Cisco 8000 PBTS Implementation (Basic)
Introduction
This post aims to describe PBTS implementation on Cisco 8000 routers.
It will go over feature operation, configuration, verification, and other notes like constraints and supported scale.
Feature Description
PBTS (Policy Based Tunnel Selection) is a feature where operator can classify incoming network traffic and forward that traffic to destination via specific MPLS traffic engineering tunnels (TE tunnel).
PBTS implementation on Cisco 8000 described in this article classifies the incoming traffic on ingress interface based on EXP field (for MPLS traffic) or prec/DSCP field (for IP traffic).
Thus it is possible, for instance, to forward traffic with specific EXP/Prec/DSCP value via a specific TE tunnel like shown in below picture.
In Cisco 8000 platform, PBTS is implemented in following manner:
Plain IPv4 / plain IPv6 / MPLS traffic arrives on ingress interface.
Using class-map inside policy-map set in inbound direction on ingress interface, traffic is classified based on MPLS EXP or IP prec/DSCP fields and assigned to specific forward-class (FC).
Each TE tunnel is associated with a specific FC.
In this way, specific traffic flow can then be steered to TE tunnel with the matching FC.
e.g.
Traffic with IP prec_6 ➜ FC 3 ➜ tunnel-te1
PBTS support on 8000 platform comes in phases.
The following constraints apply for phase 1 in IOS XR 7.5.3:
Supported PBTS over TE tunnel and also LDP-over-TE tunnel.
Supported PBTS for IPv4, IPv6, MPLS traffic.
NOT Supported PBTS for services (L3VPN, 6VPE, 6PE, L2VPN) and overlays over this prefix over TE tunnel with PBTS enabled.
NOT Supported Statically configured MPLS prefix over LDP-over-TE tunnel.
NOT Supported Statically configured MPLS prefix over TE tunnel.
NOT Supported Labeled Unicast over TE tunnel.
The NOT Supported items will be addressed in future phase in later IOS XR release.
Some important notes:
PBTS doesn’t override routing decision.
Rather the use case is if routing have multiple TE tunnel paths toward destination, then with PBTS we will be able to pick which TE tunnels should carry the traffic based on traffic’s MPLS EXP or IP prec/DSCP values.8 unique FC values are supported (class 0 to class 7).
Only one FC can be associated with a TE tunnel at any time.FC 0 is treated as the default class and doesn’t need to be explicitly configured under a TE tunnel.
If a TE tunnel is not configured with an explicit FC, it will be associated with a default FC 0.
PBTS is supported on both named tunnels and numbered tunnels.
However, using “named” tunnels is recommended.When many TE tunnels are equal best paths to same destination, they will be load balanced: up to 64 path ECMP TE tunnels can be used for a given destination.
However, this can cause issue when we have more than 64 tunnels for a given PBTS destination.
consider this config:- tunnel-te1 up to tunnel-te64:
configured with FC3, use it for FC3 traffic to destination X. - tunnel-te65 up to tunnel-te100:
configured with FC0, use it for FC0 traffic to destination X.
- tunnel-te1 up to tunnel-te64:
If we have the above config, it could happen that only FC3 paths will be programmed, causing traffic blackhole for FC0 traffic.
The recommendation is to have no more than 64 tunnel-te paths to a given destination, with 64 paths ECMP configured.
- Fallback mechanism is available:
- When any FC (except FC 0) paths are down, traffic will switch to default class FC 0 path unless fallback PBTS class is configured.
- If the fallback PBTS class path itself is not available, default class path will be used.
- If both fallback PBTS class and default class paths are not available, then traffic will be dropped.
- All TE related features (such as TE-FRR etc.) will continue to work as is.
Supported Software
This feature is introduced in IOS XR 7.5.3.
Supported Hardware
This feature is supported on Cisco 8000 platform using Silicon One Q200 ASIC.
e.g.
- fixed systems:
8201-32FH, 8202-32FH-M, 8201-24H8FH - line cards for distributed systems:
88-LC0-36FH-M, 88-LC0-36FH, 88-LC0-34H14FH
Supported Scale
Up to 1,000 TE tunnels per box and 64 paths ECMP per destination.
Note: With the following config enabled:
hw-module profile cef te-tunnel highscale-ldp-over-te-no-sr-over-srte
The scale of TE tunnels can be increased from 1,000 to 4,000. (only supported on Silicon One Q200 systems).
Configuring PBTS : Basic Configuration
Class-map configuration.
class-map match-any exp-0
match mpls experimental topmost 0
end-class-map
!
class-map match-any exp-1
match mpls experimental topmost 1
end-class-map
!
class-map match-any prec_5
match precedence 5
end-class-map
!
class-map match-any prec_6
match precedence 6
end-class-map
!
class-map match-any prec_7
match precedence 7
end-class-map
!
class-map match-any low_lat_af21
match dscp af21
end-class-map
!
class-map match-any bcast_vid_cs3
match dscp cs3
end-class-map
!
class-map match-any multimedia_conf_af41
match dscp af41
end-class-map
!
Note:
PBTS classification only works with matching directly with Prec/DSCP or MPLS EXP field, not ACL.
For instance, following classification config will not work in PBTS use case:
ipv4 access-list acl_prec_7
10 permit ipv4 any host 202.4.0.1 precedence network
!
!
class-map match-any acl_prec_7
match access-group ipv4 acl_prec_7
end-class-map
!
String class-map with forward-class using policy-map.
policy-map MY_PBTS
!
class exp-1
set forward-class 1
!
class prec_5
set forward-class 2
!
class prec_6
set forward-class 3
!
class prec_7
set forward-class 4
!
class low_lat_af21
set forward-class 5
!
class bcast_vid_cs3
set forward-class 6
!
class multimedia_conf_af41
set forward-class 7
!
class class-default
!
end-policy-map
Assign the policy-map on ingress interface in inbound direction.
interface Bundle-Ether1
service-policy input MY_PBTS
root
Assign forward-class to TE tunnels.
interface tunnel-te0
forward-class 0
!
interface tunnel-te1
forward-class 1
!
interface tunnel-te2
forward-class 2
!
interface tunnel-te3
forward-class 3
!
mpls traffic-eng
named-tunnels
tunnel-te named_4
forward-class 4
!
tunnel-te named_5
forward-class 5
!
tunnel-te named_6
forward-class 6
!
tunnel-te named_7
forward-class 7
!
!
!
When the above is configured, following PBTS path will be used:
exp-0 traffic ➜ no explicit config within policy-map ; use default FC ➜ FC 0 ➜ tunnel-te0
exp-1 traffic ➜ explicit config within policy-map ➜ FC 1 ➜ tunnel-te1
prec_5 traffic ➜ explicit config within policy-map ➜ FC 2 ➜ tunnel-te2
prec_6 traffic ➜ explicit config within policy-map ➜ FC 3 ➜ tunnel-te3
prec_7 traffic ➜ explicit config within policy-map ➜ FC 4 ➜ tunnel-te named_4
low_lat_af21 traffic ➜ explicit config within policy-map ➜ FC 5 ➜ tunnel-te named_5
bcast_vid_cs3 traffic ➜ explicit config within policy-map ➜ FC 6 ➜ tunnel-te named_6
multimedia_conf_af41 traffic ➜ explicit config within policy-map ➜ FC 7 ➜ tunnel-te named_7
all other traffic ➜ no explicit config within policy-map ; use default FC ➜ FC 0 ➜ tunnel-te0
Configuring PBTS : Optional Configuration
Optimizing hardware resource usage for forward-classes
If we know for sure which FCs that we will use, we can optimize the hardware resource usage used by ECMP for those FCs by using the following config:
hw-module profile cef cbf forward-class-list <a list consisting of 0-7 values>
e.g.
hw-module profile cef cbf forward-class-list 0 1 2 3 5
Note:
- Chassis needs to be reloaded for this config to go into effect.
- There won’t be optimization taking place if all FC is listed.
i.e.hw-module profile cef cbf forward-class-list 0 1 2 3 4 5 6 7
Custom Fallback
When TE tunnels associated with an FC go down, traffic can be redirected to another FC, any FC or chosen to be dropped via fallback PBTS configuration.
This config will override the default behavior on the box when PBTS enabled TE tunnel goes down.
We can specify sequence of preferred fallback classes to revert to when TE tunnel of an FC goes down:
RP/0/RP0/CPU0:Rean--C8201-32FH(config)#cef pbts class ?
<0-7> Forward Class number
any Any forward class
RP/0/RP0/CPU0:Rean--C8201-32FH(config)#cef pbts class 7 ?
fallback-to Fallback to configuration
RP/0/RP0/CPU0:Rean--C8201-32FH(config)#cef pbts class 7 fallback-to ?
<0-7> Fallback Class number
any Fallback to any class
drop Fallback to drop
For example, an operator that is using FC 0,1,2,3,5 can configure these following fallback paths:
cef pbts class 0 fallback-to 1 2 3 5
cef pbts class 1 fallback-to 0 2 3 5
cef pbts class 2 fallback-to 0 1 3 5
cef pbts class 3 fallback-to 0 1 2 5
cef pbts class 5 fallback-to 0 1 2 3
In this way, first FC 0 and its paths will be present as fallback class for all other classes.
If paths of FC 0 go down, then the next available FC in ascending order of 0-7 will be chosen as the fallback FC, i.e FC 1.
When paths in FC 1 go down, the next FC 2 will be chosen as fallback so on and so forth.
We can also use any as fallback instead of specifying FC number. In this way, next available FC in ascending order of 0-7 will be chosen as the fallback FC.
cef pbts class 1 fallback-to any
or even:
cef pbts class any fallback-to any
When “cef pbts class any fallback-to any” is specified, then the lowest available forward class ascending order of 0-7, is chosen as fallback for when paths to any class go down.
Keeping the above in mind, note that the following single line:
cef pbts class any fallback-to any
will actually has same effect as configuring multiple config lines like these:
cef pbts class 0 fallback-to 1 2 3 5
cef pbts class 1 fallback-to 0 2 3 5
cef pbts class 2 fallback-to 0 1 3 5
cef pbts class 3 fallback-to 0 1 2 5
cef pbts class 5 fallback-to 0 1 2 3
Operation
Behavior when no PBTS is configured
Let’s start from the basic : router’s default behavior when no PBTS is configured.
We’re going to use following topology:
Underlying network features:
- MPLS-TE cloud has ISIS for IGP, LDP for LDP-over-TE (LDPoTE), and MPLS TE tunnels.
- 8 TE tunnels with router “Rean” as head end router (where we’ll configure PBTS) and router “Musse” as tail end.
- To allow for LDPoTE session to come up, 1 TE tunnel is also created on Musse as head end and Rean as tail end.
- Configure these TE tunnels under LDP to bring up LDPoTE.
RP/0/RP0/CPU0:Rean--C8201-32FH#sh mpls traffic-eng tunnels tabular
Tue Oct 11 00:34:34.162 -07
Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te0 2 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te1 2 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te2 2 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te3 2 202.158.0.2 202.158.0.6 up Inact Head Inact
named_4 2 202.158.0.2 202.158.0.6 up Inact Head Inact
named_5 2 202.158.0.2 202.158.0.6 up Inact Head Inact
named_6 2 202.158.0.2 202.158.0.6 up Inact Head Inact
named_7 2 202.158.0.2 202.158.0.6 up Inact Head Inact
The LSP config:
group numbered_te
interface 'tunnel-te.*'
ipv4 unnumbered Loopback0
autoroute announce
!
destination 202.158.0.2
path-option 10 dynamic
!
end-group
interface tunnel-te0
apply-group numbered_te
description exp_0
!
interface tunnel-te1
apply-group numbered_te
description exp_1
!
interface tunnel-te2
apply-group numbered_te
description exp_2
!
interface tunnel-te3
apply-group numbered_te
description exp_3
!
group named_te
mpls traffic-eng
named-tunnels
tunnel-te '.*'
path-option STATIC
preference 10
computation dynamic
!
autoroute announce
!
destination 202.158.0.2
!
!
!
end-group
mpls traffic-eng
named-tunnels
tunnel-te named_4
apply-group named_te
!
tunnel-te named_5
apply-group named_te
!
tunnel-te named_6
apply-group named_te
!
tunnel-te named_7
apply-group named_te
!
!
!
Note that we have autoroute announce under all tunnels which means that these tunnels will be considered by IGP when forwarding traffic. We also have 64 paths ECMP configured to make sure all tunnels will be used.
router isis main
address-family ipv4 unicast
maximum-paths 64
!
address-family ipv6 unicast
maximum-paths 64
!
Here’s CEF output for prefix “102.1.0.0/16” that is using the TE tunnels.
RP/0/RP0/CPU0:Rean--C8201-32FH#sh cef 102.1.0.0/16
Tue Oct 11 00:53:08.180 -07
102.1.0.0/16, version 2683, internal 0x1000001 0xf0 (ptr 0x940b61b0) [1], 0x400 (0x931456e8), 0x0 (0x0)
Updated Oct 11 00:01:09.979
Prefix Len 16, traffic index 0, precedence n/a, priority 15
gateway array (0x92faa2d0) reference count 2, flags 0x0, source rib (7), 0 backups
[3 type 3 flags 0x8401 (0xa96978c8) ext 0x0 (0x0)]
LW-LDI[type=3, refc=1, ptr=0x931456e8, sh-ldi=0xa96978c8]
gateway array update type-time 1 Oct 11 00:01:09.976
LDI Update time Oct 11 00:32:31.661
LW-LDI-TS Oct 11 00:32:31.665
via 202.158.0.2/32, tunnel-te1, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 0 NHID 0x0 [0xa933e428 0x0]
next hop 202.158.0.2/32
local adjacency
via 202.158.0.2/32, named_4, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 1 NHID 0x0 [0xa933eb18 0x0]
next hop 202.158.0.2/32
local adjacency
via 202.158.0.2/32, named_5, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 2 NHID 0x0 [0xa933ed68 0x0]
next hop 202.158.0.2/32
local adjacency
via 202.158.0.2/32, named_6, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 3 NHID 0x0 [0xa933efb8 0x0]
next hop 202.158.0.2/32
local adjacency
via 202.158.0.2/32, named_7, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 4 NHID 0x0 [0xa933f208 0x0]
next hop 202.158.0.2/32
local adjacency
via 202.158.0.2/32, tunnel-te0, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 5 NHID 0x0 [0xa933e1d8 0x0]
next hop 202.158.0.2/32
local adjacency
via 202.158.0.2/32, tunnel-te2, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 6 NHID 0x0 [0xa933e678 0x0]
next hop 202.158.0.2/32
local adjacency
via 202.158.0.2/32, tunnel-te3, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 7 NHID 0x0 [0xa933e8c8 0x0]
next hop 202.158.0.2/32
local adjacency
Load distribution: 0 1 2 3 4 5 6 7 (refcount 3)
Hash OK Interface Address
0 Y tunnel-te1 point2point
1 Y named_4 point2point
2 Y named_5 point2point
3 Y named_6 point2point
4 Y named_7 point2point
5 Y tunnel-te0 point2point
6 Y tunnel-te2 point2point
7 Y tunnel-te3 point2point
Now let’s try sending traffic flows toward destinations that fall within this subnet 102.1.0.0/16. All flows have different /32 desination IPs, but they all have same IP precedence field set with value 7.
“show interface accounting” output:
named_4
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 9389 1032790
named_5
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 4224 464640
named_6
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 7981 877910
named_7
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 8918 980980
tunnel-te0
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 5633 619630
tunnel-te1
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 7981 877910
tunnel-te2
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 9854 1083940
tunnel-te3
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 6101 671110
Note that:
- All tunnels are currently being used.
Recall that by default all tunnels are assigned as FC0 where non-PBTS-classified traffic are forwarded. - All tunnels are being utilized since we have ECMP configured.
This is behavior that we will see if PBTS is not configured.
Behavior when PBTS is configured for plain IP traffic.
Now let’s configure following PBTS config:
class-map match-any prec_7
match precedence 7
end-class-map
!
!
policy-map MY_PBTS
class prec_7
set forward-class 4
!
class class-default
!
end-policy-map
!
interface BE1
service-policy input MY_PBTS
!
mpls traffic-eng
named-tunnels
tunnel-te named_4
forward-class 4
!
!
!
Note that with the above configured, we will have PBTS to match traffic with IP prec 7 and send it to destination via tunnel-te named_4.
Commit that config and send traffic again. Now you will see following result in “show interface accounting”:
named_4
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 87496 9624560
No accounting statistics available for named_5
No accounting statistics available for named_6
No accounting statistics available for named_7
No accounting statistics available for tunnel-te0
No accounting statistics available for tunnel-te1
No accounting statistics available for tunnel-te2
No accounting statistics available for tunnel-te3
Now all traffic with IP prec 7 is sent via tunnel-te named_4 as configured.
Let’s try sending other flows with IP prec 5, which TE tunnel it will take?
Following result will show in “show interface accounting”:
named_4
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 58410 6425100
named_5
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 5941 653510
named_6
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 4591 505010
named_7
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 5941 653510
tunnel-te0
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 5672 623920
tunnel-te1
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 4864 535040
tunnel-te2
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 2973 327030
tunnel-te3
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 4593 505230
We’re sending 58,410 packets with IP prec 7, it’s forwarded using TE tunnel named_4. The rest of traffic is sent using other tunnels as we have ECMP.
Recall that unclassified traffic will simply take TE tunnels that have no FC explicitly configured (i.e. tunnels that are assigned by default to forward class FC 0).
Behavior when PBTS is configured for MPLS traffic.
We can also run LDP over these TE tunnels so that LDP FEC can also take benefits of PBTS.
Since LDP is using MPLS forwarding, we will deal with 2 types of incoming traffic for this use case:
- MPLS encapsulated traffic
PBTS will classify based on MPLS EXP bits and then do label swap-push toward the matching TE tunnel.
We don’t classify MPLS traffic based on the inner payload. - Plain IP traffic
PBTS will classify based on IP prec/DSCP bits and then do label-push toward the matching TE tunnel.
Let’s activate LDP now on router “Rean”.
mpls ldp
log
neighbor
!
router-id 202.158.0.6
interface Bundle-Ether1
!
interface tunnel-te0
!
interface tunnel-te1
!
interface tunnel-te2
!
interface tunnel-te3
!
interface tunnel-te named_4
!
interface tunnel-te named_5
!
interface tunnel-te named_6
!
interface tunnel-te named_7
!
!
now sh cef shows local label and labels imposed (because LDP control plane is now in use).
RP/0/RP0/CPU0:Rean--C8201-32FH#sh cef 102.1.0.0/16
Tue Oct 11 02:01:57.245 -07
102.1.0.0/16, version 2283, internal 0x1000001 0x30 (ptr 0x940b61b0) [1], 0x600 (0x93145a18), 0xa20 (0xa9875588)
Updated Oct 11 02:00:00.630
Prefix Len 16, traffic index 0, precedence n/a, priority 3, encap-id 0x1001000000001
gateway array (0x92fa9d60) reference count 6, flags 0x68, source lsd (5), 1 backups
[3 type 5 flags 0x208401 (0x94c754b8) ext 0x0 (0x0)]
LW-LDI[type=5, refc=3, ptr=0x93145a18, sh-ldi=0x94c754b8]
gateway array update type-time 1 Oct 11 01:59:56.590
LDI Update time Oct 11 01:59:56.603
LW-LDI-TS Oct 11 02:00:00.630
via 202.158.0.2/32, tunnel-te1, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 0 NHID 0x0 [0xa933e300 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_4, 5 dependencies, weight 0, forward class 4 [flags 0x0]
path-idx 1 NHID 0x0 [0xa933e9f0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_5, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 2 NHID 0x0 [0xa933ec40 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_6, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 3 NHID 0x0 [0xa933ee90 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_7, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 4 NHID 0x0 [0xa933f0e0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te0, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 5 NHID 0x0 [0xa933e0b0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te2, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 6 NHID 0x0 [0xa933e550 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te3, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 7 NHID 0x0 [0xa933e7a0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
Weight distribution:
slot 0, weight 0, normalized_weight 1, class 0
slot 1, weight 0, normalized_weight 1, class 0
slot 2, weight 0, normalized_weight 1, class 0
slot 3, weight 0, normalized_weight 1, class 0
slot 4, weight 0, normalized_weight 1, class 0
slot 5, weight 0, normalized_weight 1, class 0
slot 6, weight 0, normalized_weight 1, class 0
slot 7, weight 0, normalized_weight 1, forward class 4
PBTS class information:
class 0: 7 paths, offset 0
forward class 4: 1 paths, offset 7
Load distribution: 0 1 2 3 4 5 6 7 (refcount 3)
Hash OK Interface Address
0 Y tunnel-te1 point2point
1 Y named_5 point2point
2 Y named_6 point2point
3 Y named_7 point2point
4 Y tunnel-te0 point2point
5 Y tunnel-te2 point2point
6 Y tunnel-te3 point2point
7 Y named_4 point2point
Also pay attention to this part from output above that only shows when PBTS is active:
PBTS class information:
class 0: 7 paths, offset 0 ← 7 TE tunnels for FC0 (hash 0 to hash 6)
forward class 4: 1 paths, offset 7 ← 1 TE tunnel for FC4 (hash 7)
Load distribution: 0 1 2 3 4 5 6 7 (refcount 3)
Hash OK Interface Address
0 Y tunnel-te1 point2point ← FC0 tunnel
1 Y named_5 point2point ← FC0 tunnel
2 Y named_6 point2point ← FC0 tunnel
3 Y named_7 point2point ← FC0 tunnel
4 Y tunnel-te0 point2point ← FC0 tunnel
5 Y tunnel-te2 point2point ← FC0 tunnel
6 Y tunnel-te3 point2point ← FC0 tunnel
7 Y named_4 point2point ← FC4 tunnel
From sh cef output above, we also know that prefix 102.1.0.0/16 has local MPLS label 24014.
We can also get PBTS information based on MPLS label info by referencing that local label.
This command will give same forwarding info as when we referenced the prefix instead of the label.
sh cef mpls local-label 24014 eoS detail
Tue Oct 11 02:16:23.976 -07
Label/EOS 24014/1, Label-type LDP, version 2283, internal 0x1000001 0x30 (ptr 0x94d4b178) [1], 0x600 (0x93145a18), 0xa20 (0xa9875588)
Updated Oct 11 02:00:00.629
Prefix Len 21, traffic index 0, precedence n/a, priority 3, encap-id 0x1001000000001
gateway array (0x92fa9d60) reference count 6, flags 0x68, source lsd (5), 0 backups
[3 type 5 flags 0x208401 (0x94c754b8) ext 0x0 (0x0)]
LW-LDI[type=5, refc=3, ptr=0x93145a18, sh-ldi=0x94c754b8]
gateway array update type-time 1 Oct 11 01:59:56.589
LDI Update time Oct 11 01:59:56.602
LW-LDI-TS Oct 11 02:00:00.629
via 202.158.0.2/32, tunnel-te1, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 0 NHID 0x0 [0xa933e300 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_4, 5 dependencies, weight 0, forward class 4 [flags 0x0]
path-idx 1 NHID 0x0 [0xa933e9f0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_5, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 2 NHID 0x0 [0xa933ec40 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_6, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 3 NHID 0x0 [0xa933ee90 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_7, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 4 NHID 0x0 [0xa933f0e0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te0, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 5 NHID 0x0 [0xa933e0b0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te2, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 6 NHID 0x0 [0xa933e550 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te3, 7 dependencies, weight 0, class 0 [flags 0x0]
path-idx 7 NHID 0x0 [0xa933e7a0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
Weight distribution:
slot 0, weight 0, normalized_weight 1, class 0
slot 1, weight 0, normalized_weight 1, class 0
slot 2, weight 0, normalized_weight 1, class 0
slot 3, weight 0, normalized_weight 1, class 0
slot 4, weight 0, normalized_weight 1, class 0
slot 5, weight 0, normalized_weight 1, class 0
slot 6, weight 0, normalized_weight 1, class 0
slot 7, weight 0, normalized_weight 1, forward class 4
PBTS class information:
class 0: 7 paths, offset 0
forward class 4: 1 paths, offset 7
Load distribution: 0 1 2 3 4 5 6 7 (refcount 3)
Hash OK Interface Address
0 Y tunnel-te1 point2point
1 Y named_5 point2point
2 Y named_6 point2point
3 Y named_7 point2point
4 Y tunnel-te0 point2point
5 Y tunnel-te2 point2point
6 Y tunnel-te3 point2point
7 Y named_4 point2point
Since now LDP control plane is active, let’s try classify based on MPLS EXP in addition to the existing classification based on IP prec.
We will configure PBTS to steer traffic with MPLS EXP 1 to tunnel-te1.
class-map match-any exp-1
match mpls experimental topmost 1
end-class-map
!
!
policy-map MY_PBTS
class exp-1
set forward-class 1
!
class prec_7
set forward-class 4
!
class class-default
!
end-policy-map
!
interface Bundle-Ether1
service-policy input MY_PBTS
!
interface tunnel-te1
apply-group numbered_te
forward-class 1
!
Commit that and send traffic flow with MPLS EXP 1 and another flow of plain IP with prec 7.
Following result will show in “show interface accounting”:
named_4
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 29479 3242690
No accounting statistics available for named_5
No accounting statistics available for named_6
No accounting statistics available for named_7
No accounting statistics available for tunnel-te0
tunnel-te1
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 11557 1225042
No accounting statistics available for tunnel-te2
No accounting statistics available for tunnel-te3
We’re sending 11,557 MPLS encapsulated packet with EXP bit 1, and it shows that they’re forwarded using tunnel-te1.
We’re sending 29,479 plain IP packet with prec bit 7, and it shows that they’re forwarded using tunnel named_4.
Behavior when default fallback is taking place.
Now what happens if TE tunnel that is carrying PBTS steered traffic goes down?
Let’s see the fallback mechanism that is available by default.
Recall from previous example that we configured MPLS encapsulated packet with EXP bit 1 to be forwarded using tunnel-te1.
exp-1 traffic ➜ explicit config within policy-map ➜ FC 1 ➜ tunnel-te1
Also note that we have 8 TE tunnels, only 2 of which are configured with FC.
RP/0/RP0/CPU0:Rean--C8201-32FH#sh run formal | i forward-class
interface tunnel-te1 forward-class 1
mpls traffic-eng named-tunnels tunnel-te named_4 forward-class 4
Now let’s shut down tunnel-te1.
interface tunnel-te1
shutdown
!
And send related traffic and show interface accounting:
No accounting statistics available for named_4
named_5
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 2112 223872
named_6
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 2209 234154
named_7
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 1826 193556
tunnel-te0
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 2113 223978
No accounting statistics available for tunnel-te1
tunnel-te2
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 1825 193450
tunnel-te3
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 2210 234260
Note that now exp-1 traffic is forwarded using all TE tunnels that are NOT configured with FC.
These tunnels that have no FC configured are associated with FC0 and we fallback PBTS steered traffic by default to these tunnels when the primary tunnel goes down.
TE tunnel named_4, on the other hand, is not forwarding the fallback traffic since it’s explicitly configured with FC4.
Now let’s try to shut down all tunnels that have no FC configured.
What happens with PBTS steered traffic if the fallback tunnels themselves are down?
interface tunnel-te0
shutdown
!
interface tunnel-te2
shutdown
!
interface tunnel-te3
shutdown
!
mpls traffic-eng
named-tunnels
tunnel-te named_5
shutdown
!
tunnel-te named_6
shutdown
!
tunnel-te named_7
shutdown
!
!
!
RP/0/RP0/CPU0:Rean--C8201-32FH#sh mpls traffic-eng tunnels tabular
Wed Oct 12 02:28:14.189 -07
Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te0 0 202.158.0.2 0.0.0.0 down Inact Head Inact
tunnel-te1 0 202.158.0.2 0.0.0.0 down Inact Head Inact
tunnel-te2 0 202.158.0.2 0.0.0.0 down Inact Head Inact
tunnel-te3 0 202.158.0.2 0.0.0.0 down Inact Head Inact
named_4 2 202.158.0.2 202.158.0.6 up Inact Head Inact
named_5 0 202.158.0.2 0.0.0.0 down Inact Head Inact
named_6 0 202.158.0.2 0.0.0.0 down Inact Head Inact
named_7 0 202.158.0.2 0.0.0.0 down Inact Head Inact
Send traffic again, and check interface accounting:
No accounting statistics available for named_4
No accounting statistics available for named_5
No accounting statistics available for named_6
No accounting statistics available for named_7
No accounting statistics available for tunnel-te0
No accounting statistics available for tunnel-te1
No accounting statistics available for tunnel-te2
No accounting statistics available for tunnel-te3
No TE tunnels are forwarding traffic now, traffic is actually being dropped as per the designed fallback behavior:
- When any FC (except FC 0) paths are down, traffic will switch to default class FC 0 path unless fallback PBTS class is configured.
- If the fallback PBTS class path itself is not available, default class path will be used.
- If both fallback PBTS class and default class paths are not available, then traffic will be dropped.
Behavior when custom fallback is taking place.
We have discussed default fallback behavior above.
We can actually customize the fallback behavior using following CLI config:
cef pbts class <> fallback-to <>
RP/0/RP0/CPU0:Rean--C8201-32FH(config)#cef pbts class ?
<0-7> Forward Class number
any Any forward class
RP/0/RP0/CPU0:Rean--C8201-32FH(config)#cef pbts class 7 ?
fallback-to Fallback to configuration
RP/0/RP0/CPU0:Rean--C8201-32FH(config)#cef pbts class 7 fallback-to ?
<0-7> Fallback Class number
any Fallback to any class
drop Fallback to drop
Let’s try to customize fallback order in our setup.
First, bring up all TE tunnels and start fresh.
RP/0/RP0/CPU0:Rean--C8201-32FH#sh mpls traffic-eng tunnels tabular
Wed Oct 12 02:36:01.791 -07
Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te0 3 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te1 3 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te2 3 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te3 3 202.158.0.2 202.158.0.6 up Inact Head Inact
named_4 2 202.158.0.2 202.158.0.6 up Inact Head Inact
named_5 3 202.158.0.2 202.158.0.6 up Inact Head Inact
named_6 3 202.158.0.2 202.158.0.6 up Inact Head Inact
named_7 3 202.158.0.2 202.158.0.6 up Inact Head Inact
Recall again that we have the following configured:
exp-1 traffic ➜ explicit config within policy-map ➜ FC 1 ➜ tunnel-te1
Also recall that we have 8 TE tunnels, only 2 of which are configured with FC.
RP/0/RP0/CPU0:Rean--C8201-32FH#sh run formal | i forward-class
interface tunnel-te1 forward-class 1
mpls traffic-eng named-tunnels tunnel-te named_4 forward-class 4
Now let’s configure the custom fallback as follows:
cef pbts class 1 fallback-to 4
Then shut tunnel-te1 again and send traffic.
You will get this output from show cef:
RP/0/RP0/CPU0:Rean--C8201-32FH#sh cef mpls local-label 24014 eoS detail
Wed Oct 12 02:46:58.227 -07
Label/EOS 24014/1, Label-type LDP, version 2340, internal 0x1000001 0x30 (ptr 0x94d4b178) [1], 0x600 (0x93133808), 0xa20 (0xa9ae8170)
Updated Oct 12 02:46:46.581
Prefix Len 21, traffic index 0, precedence n/a, priority 3, encap-id 0x1001000000001
gateway array (0x92faa588) reference count 6, flags 0x68, source lsd (5), 0 backups
[3 type 5 flags 0x208401 (0x94c6a2b0) ext 0x0 (0x0)]
LW-LDI[type=5, refc=3, ptr=0x93133808, sh-ldi=0x94c6a2b0]
gateway array update type-time 1 Oct 12 02:46:46.571
LDI Update time Oct 12 02:46:46.577
LW-LDI-TS Oct 12 02:46:46.581
via 202.158.0.2/32, named_4, 5 dependencies, weight 0, forward class 4 [flags 0x0]
path-idx 0 NHID 0x0 [0xa933e9f0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_5, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 1 NHID 0x0 [0xa933e300 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_6, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 2 NHID 0x0 [0xa933efb8 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_7, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 3 NHID 0x0 [0xa933e1d8 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te0, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 4 NHID 0x0 [0xa933e8c8 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te2, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 5 NHID 0x0 [0xa933e0b0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te3, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 6 NHID 0x0 [0xa933e7a0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
Weight distribution:
slot 0, weight 0, normalized_weight 1, class 0
slot 1, weight 0, normalized_weight 1, class 0
slot 2, weight 0, normalized_weight 1, class 0
slot 3, weight 0, normalized_weight 1, class 0
slot 4, weight 0, normalized_weight 1, class 0
slot 5, weight 0, normalized_weight 1, class 0
slot 6, weight 0, normalized_weight 1, forward class 4
PBTS class information:
class 0: 6 paths, offset 0
forward class 1: 1 paths, offset 6, fallback-to forward class 4
forward class 4: 1 paths, offset 6
Load distribution: 0 1 2 3 4 5 6 (refcount 3)
Hash OK Interface Address
0 Y named_5 point2point
1 Y named_6 point2point
2 Y named_7 point2point
3 Y tunnel-te0 point2point
4 Y tunnel-te2 point2point
5 Y tunnel-te3 point2point
6 Y named_4 point2point
Note that since we shut tunnel-te1, now forward class 1 points to fallback tunnel named_4 as configured.
Traffic accounting result when we’re sending FC 1 traffic:
named_4
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 8683 920398
No accounting statistics available for named_5
No accounting statistics available for named_6
No accounting statistics available for named_7
No accounting statistics available for tunnel-te0
No accounting statistics available for tunnel-te1
No accounting statistics available for tunnel-te2
No accounting statistics available for tunnel-te3
Now FC 1 traffic fell back to tunnel named_4 which is associated with FC4.
Remember that without custom config, FC1 traffic will fall back to FC0 tunnels by default.
Similarly we can configure this kind of fallback for other FC.
For instance:
cef pbts class 0 fallback-to 4
cef pbts class 1 fallback-to 4
cef pbts class 2 fallback-to 4
...
cef pbts class 7 fallback-to 4
or use this one line to cover all FCs:
cef pbts class any fallback-to 4
Now back to our example, what happens if the fallback FC4 TE tunnel also goes down?
Let’s try that out, shut FC4 tunnel now:
mpls traffic-eng named-tunnels tunnel-te named_4 shut
RP/0/RP0/CPU0:Rean--C8201-32FH#sh mpls traffic-eng tunnels tabular
Tue Oct 18 09:21:45.884 -07
Tunnel LSP Destination Source Tun FRR LSP Path
Name ID Address Address State State Role Prot
----------------- ----- --------------- --------------- ------ ------ ---- -----
tunnel-te0 3 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te1 0 202.158.0.2 0.0.0.0 down Inact Head Inact
tunnel-te2 3 202.158.0.2 202.158.0.6 up Inact Head Inact
tunnel-te3 3 202.158.0.2 202.158.0.6 up Inact Head Inact
named_4 0 202.158.0.2 0.0.0.0 down Inact Head Inact
named_5 3 202.158.0.2 202.158.0.6 up Inact Head Inact
named_6 3 202.158.0.2 202.158.0.6 up Inact Head Inact
named_7 3 202.158.0.2 202.158.0.6 up Inact Head Inact
And send traffic again to FC1.
Here’s the resulting traffic path for traffic with exp-1:
No accounting statistics available for named_4
named_5
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 1820 192920
named_6
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 1906 202036
named_7
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 1824 193344
tunnel-te0
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 1734 183804
tunnel-te2
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 2169 229914
tunnel-te3
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 1651 175006
Since tunnel-te1 is down, and the fallback path named_4 is also down, traffic will fall back again to FC0 TE tunnels.
We also have option to specify a list of FCs to be used as fallback.
Instead of this:
cef pbts class 1 fallback-to 4
We can have something like this:
cef pbts class 1 fallback-to 4 5
With the above configured, let’s now assign FC5 to tunnel-te named_5.
mpls traffic-eng named-tunnels tunnel-te named_5 forward-class 5
Since tunnel-te1 is down, fallback path named_4 is down, traffic should now use FC5 TE tunnel as per configuration, which is tunnel-te named_5.
Let’s see if that’s really the path that the traffic would take:
RP/0/RP0/CPU0:Rean--C8201-32FH#sh cef mpls local-label 24014 eoS detail
Sun Dec 11 23:45:45.887 -07
Label/EOS 24014/1, Label-type LDP, version 81, internal 0x1000001 0x30 (ptr 0x9a1e3550) [1], 0x600 (0x931b8378), 0xa20 (0xa9afb168)
Updated Dec 11 23:26:14.199
Prefix Len 21, traffic index 0, precedence n/a, priority 3, encap-id 0x1001300000001
gateway array (0x92fea280) reference count 6, flags 0x68, source lsd (5), 0 backups
[3 type 5 flags 0x200401 (0x9a1112b0) ext 0x0 (0x0)]
LW-LDI[type=5, refc=3, ptr=0x931b8378, sh-ldi=0x9a1112b0]
gateway array update type-time 4 Dec 11 23:43:48.828
LDI Update time Dec 11 23:44:03.254
LW-LDI-TS Dec 11 23:44:03.255
via 202.158.0.2/32, named_5, 5 dependencies, weight 0, forward class 5 [flags 0x0]
path-idx 0 NHID 0x0 [0xa97e1c40 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_6, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 1 NHID 0x0 [0xa97e1e90 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, named_7, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 2 NHID 0x0 [0xa97e20e0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te0, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 3 NHID 0x0 [0xa97e10b0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te2, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 4 NHID 0x0 [0xa97e1550 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
via 202.158.0.2/32, tunnel-te3, 5 dependencies, weight 0, class 0 [flags 0x0]
path-idx 5 NHID 0x0 [0xa97e17a0 0x0]
next hop 202.158.0.2/32
local adjacency
local label 24014 labels imposed {ImplNull}
Weight distribution:
slot 0, weight 0, normalized_weight 1, class 0
slot 1, weight 0, normalized_weight 1, class 0
slot 2, weight 0, normalized_weight 1, class 0
slot 3, weight 0, normalized_weight 1, class 0
slot 4, weight 0, normalized_weight 1, class 0
slot 5, weight 0, normalized_weight 1, forward class 5
PBTS class information:
class 0: 5 paths, offset 0
forward class 1: 1 paths, offset 5, fallback-to forward class 5
forward class 5: 1 paths, offset 5
Load distribution: 0 1 2 3 4 5 (refcount 3)
Hash OK Interface Address
0 Y named_6 point2point
1 Y named_7 point2point
2 Y tunnel-te0 point2point
3 Y tunnel-te2 point2point
4 Y tunnel-te3 point2point
5 Y named_5 point2point
show interface accounting …
No accounting statistics available for named_4
named_5
Protocol Pkts In Chars In Pkts Out Chars Out
MPLS 0 0 4817 510602
No accounting statistics available for named_6
No accounting statistics available for named_7
No accounting statistics available for tunnel-te0
No accounting statistics available for tunnel-te2
No accounting statistics available for tunnel-te3
Now traffic falls back to FC5 tunnel-te named_5 as expected.
That is all for basic PBTS operation overview.
Read on to get full configuration example for both head-end router and tail-end router.
Full Configuration Example
Head-end / PBTS router
group named_te
mpls traffic-eng
named-tunnels
tunnel-te '.*'
path-option STATIC
preference 10
computation explicit chu_pyke_peyto_turin
!
autoroute announce
!
destination 202.158.0.2
fast-reroute
!
!
!
end-group
group numbered_te
interface 'tunnel-te.*'
ipv4 unnumbered Loopback0
autoroute announce
!
destination 202.158.0.2
fast-reroute
path-option 10 explicit name chu_pyke_peyto_turin
!
end-group
explicit-path name chu_pyke_peyto_turin
index 1 next-address strict ipv4 unicast 103.1.3.3
index 2 next-address strict ipv4 unicast 103.1.6.5
index 3 next-address strict ipv4 unicast 103.1.7.2
!
ipv4 unnumbered mpls traffic-eng Loopback0
ipv4 source-route
interface Bundle-Ether1
ipv4 address 103.1.1.6 255.255.255.0
ipv6 address 103:1:1::6/64
lacp mode on
!
interface Bundle-Ether2
ipv4 address 103.1.3.6 255.255.255.0
ipv6 address 103:1:3::6/64
lacp mode on
!
interface Loopback0
ipv4 address 202.158.0.6 255.255.255.255
ipv6 address 202:158::6/128
!
interface tunnel-te0
apply-group numbered_te
forward-class 0
!
interface tunnel-te1
apply-group numbered_te
forward-class 1
!
interface tunnel-te2
apply-group numbered_te
forward-class 2
!
interface tunnel-te3
apply-group numbered_te
forward-class 3
!
router isis main
net 47.0005.6666.6666.6666.00
nsr
distribute link-state
log adjacency changes
address-family ipv4 unicast
metric-style wide
mpls traffic-eng level-1-2
mpls traffic-eng router-id Loopback0
router-id Loopback0
!
address-family ipv6 unicast
metric-style wide
router-id Loopback0
!
interface Bundle-Ether1
point-to-point
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
interface Bundle-Ether2
point-to-point
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
interface Loopback0
passive
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
!
rsvp
interface Bundle-Ether2
bandwidth 10000000
!
!
mpls traffic-eng
interface Bundle-Ether2
!
logging events all
auto-tunnel backup
timers removal unused 5
tunnel-id min 65000 max 65500
!
reoptimize 604800
bandwidth-accounting
!
soft-preemption
!
named-tunnels
tunnel-te named_4
apply-group named_te
forward-class 4
!
tunnel-te named_5
apply-group named_te
forward-class 5
!
tunnel-te named_6
apply-group named_te
forward-class 6
!
tunnel-te named_7
apply-group named_te
forward-class 7
!
!
!
mpls ldp
log
neighbor
!
router-id 202.158.0.6
interface Bundle-Ether1
!
interface tunnel-te0
!
interface tunnel-te1
!
interface tunnel-te2
!
interface tunnel-te3
!
interface tunnel-te named_4
!
interface tunnel-te named_5
!
interface tunnel-te named_6
!
interface tunnel-te named_7
!
!
PBTS configuration
class-map match-any exp-0
match mpls experimental topmost 0
end-class-map
!
class-map match-any exp-1
match mpls experimental topmost 1
end-class-map
!
class-map match-any prec_5
match precedence 5
end-class-map
!
class-map match-any prec_6
match precedence 6
end-class-map
!
class-map match-any prec_7
match precedence 7
end-class-map
!
class-map match-any low_lat_af21
match dscp af21
end-class-map
!
class-map match-any bcast_vid_cs3
match dscp cs3
end-class-map
!
class-map match-any multimedia_conf_af41
match dscp af41
end-class-map
!
policy-map MY_PBTS
!
class exp-1
set forward-class 1
!
class prec_5
set forward-class 2
!
class prec_6
set forward-class 3
!
class prec_7
set forward-class 4
!
class low_lat_af21
set forward-class 5
!
class bcast_vid_cs3
set forward-class 6
!
class multimedia_conf_af41
set forward-class 7
!
class class-default
!
end-policy-map
interface Bundle-Ether1
service-policy input MY_PBTS
root
Tail-end router
No special config is needed here, as PBTS is only configured on head-end router.
explicit-path name to_rean
index 1 next-address strict ipv4 unicast 200.4.0.1
index 2 next-address strict ipv4 unicast 103.1.3.6
!
ipv4 unnumbered mpls traffic-eng Loopback0
interface Loopback0
ipv4 address 202.158.0.2 255.255.255.255
ipv6 address 202:158::2/128
!
interface tunnel-te1
ipv4 unnumbered Loopback0
autoroute announce
!
destination 202.158.0.6
path-option 10 explicit name to_rean
!
interface TenGigE0/0/0/0.1
ipv4 address 200.4.0.2 255.255.0.0
ipv6 address 200:4::2/64
encapsulation dot1q 1
!
interface TenGigE0/0/0/32.1
ipv4 address 102.1.1.1 255.255.0.0
ipv6 address 102:1:1::1/64
encapsulation dot1q 1
!
router isis main
net 47.0005.2222.2222.2222.00
nsr
distribute link-state
log adjacency changes
address-family ipv4 unicast
metric-style wide
mpls traffic-eng level-1-2
mpls traffic-eng router-id Loopback0
router-id Loopback0
!
address-family ipv6 unicast
metric-style wide
router-id Loopback0
!
interface Loopback0
passive
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
interface TenGigE0/0/0/0.1
point-to-point
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
interface TenGigE0/0/0/32.1
passive
address-family ipv4 unicast
!
address-family ipv6 unicast
!
!
!
rsvp
interface TenGigE0/0/0/0.1
bandwidth 10000000
!
!
mpls traffic-eng
interface TenGigE0/0/0/0.1
logging events all
reoptimize 604800
bandwidth-accounting
!
soft-preemption
!
!
mpls ldp
router-id 202.158.0.2
interface tunnel-te1
!
!
Verification Commands
See PBTS path based on IP info:
sh cef 102.1.0.0/16
See PBTS path based on MPLS LDP info:
sh mpls ldp forwarding 101.1.0.0/16 (grab `Label In`)
sh cef mpls local-label <label_in> eoS detail
Check if PBTS policy map is in use:
sh qos interface <ingress interface> input
Check whether traffic is taking correct tunnel-te:
sh interface tunnel-te <> accounting
Logs to get in case of issues
Basic info:
show ofa trace | inc forward_class | file harddisk:/0614a_show_ofa_trace.txt
show cef 102.1.0.0/16 hardware egress loc 0/RP0/CPU0 | file harddisk:/0614a_show_cef_hw_egress_ipv4.txt
show cef ipv6 102:1:1::2 hardware egress loc 0/RP0/CPU0 | file harddisk:/0614a_show_cef_hw_egress_ipv6.txt
show tech platform-fwd file harddisk:/0614a_show_tech_platform_fwd
show tech ofa file harddisk:/0614a_show_tech_ofa
show tech fabric file harddisk:/0614a_show_tech_fabric
show tech mpls lsd file harddisk:/0614a_show_tech_mpls_lsd
show tech mpls traffic-eng file harddisk:/0614a_show_tech_mpls_te
show tech cef file harddisk:/0614a_show_tech_cef
SDK chain info:
show controllers npu debugshell 0 "script print_prefix 0 102.1.0.0" loc 0/RP0/CPU0 | file harddisk:/0614a_show_sdk_chain_ipv4.txt
show controllers npu debugshell 0 "script print_prefix 0 102:1:1::" loc 0/RP0/CPU0 | file harddisk:/0614a_show_sdk_chain_ipv6.txt
Conclusion
PBTS offers additional flexibility in utilizing MPLS-TE tunnels.
Instead of having to use all tunnels in an ECMP manner, users can now steer specific traffic streams to use only certain tunnels.
The feature also comes with default fallback feature which can be customized to offer even more failover flexibility. When there is failure affecting the primary tunnels, traffic can fall back to back up tunnels as configured.
The feature is simple to configure and will be a nice addition to any MPLS-TE engineers toolbox.
Future:
PBTS phase 2 in IOS-XR 7.5.4 will add more capability to PBTS when it comes to steering overlay services to TE tunnels.
We will describe phase 2 feature in future document.
Glossary
EXP : “Experimental” bits field on an MPLS header
Prec : “Precedence” bits field on an IPv4 header
DSCP : “Differentiated Service Code Point” bits field on an IPv4/IPv6 header
TE : Traffic engineering
TE tunnel / tunnel-te : MPLS TE tunnel created by user to carry traffic via label switching
FC : Forward-class
LDPoTE : LDP-over-TE
ECMP : Equal cost multi paths
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