Volume 1 4.16 Inter AS C

I'm revisiting the volume 1 lads to refresh on some of the finer points.  I just completed 4.16 which is the Inter AS opt C lab and I came across an issue with XR, maybe a bug, maybe a process problem.

Anyway XR1 (ASBR) was allocating labels for the routes it received from R1 (other ASBR).  XR1 has link local LDP peerings to R4 and XR2 and all looks dandy there.  The problem is the LFIB on R4 and XR2 were reporting the egress label for R1s prefixes as no label. I did all the usual checking, interfaces runnign correctly, neighbours properly discovered but nothing so I assumed XR1 was the problem given both its LDP peers had the same issue. I did a commit replace/rollback super-combo and the problem was fixed. 

#allocating labels locally on XR1

16006  20          2.2.2.2/32                      12.1.19.1       0
16007  19          5.5.5.5/32                      12.1.19.1       0

RP/0/0/CPU0:XR1(config-static-afi)#do sho mpls int
Fri Sep 20 20:39:48.140 UTC
Interface                  LDP      Tunnel   Enabled
-------------------------- -------- -------- --------
GigabitEthernet0/1/0/0.419 Yes      No       Yes
GigabitEthernet0/1/0/0.1920 Yes     No       Yes
RP/0/0/CPU0:XR1(config-static-afi)#commit replace

This commit will replace or remove the entire running configuration. This
operation can be service affecting.
Do you wish to proceed? [no]: yes
RP/0/0/CPU0:Sep 20 20:42:21.465 : bgp[139]: %ROUTING-BGP-5-ADJCHANGE : neighbor 12.1.19.1 Down - Router ID changed (VRF: default)
RP/0/0/CPU0:Sep 20 20:42:21.519 : isis[285]: %ROUTING-ISIS-5-ADJCHANGE : Adjacency to XR2 (GigabitEthernet0/1/0/0.1920) (L2) Down, Interface state down
RP/0/0/CPU0:Sep 20 20:42:25.906 : ike[233]: %SECURITY-IKE-4-WARNING : You may want to configure a hostname
RP/0/0/CPU0:Sep 20 20:42:25.994 : ike[233]: %SECURITY-IKE-4-WARNING : You may want to configure a domain-name
RP/0/0/CPU0:Sep 20 20:42:27.421 : config[65749]: %MGBL-CONFIG-6-DB_COMMIT : Configuration committed by user 'xr1'. Use 'show configuration commit changes 1000001331' to view the changes.
RP/0/0/CPU0:ios(config-static-afi)#
RP/0/0/CPU0:ios(config-static-afi)#
RP/0/0/CPU0:ios(config-static-afi)#exi
RP/0/0/CPU0:ios(config-static)#exi
RP/0/0/CPU0:ios(config)#exi
RP/0/0/CPU0:Sep 20 20:43:15.655 : config[65749]: %MGBL-SYS-5-CONFIG_I : Configured from console by xr1
RP/0/0/CPU0:ios#
RP/0/0/CPU0:ios#
RP/0/0/CPU0:ios#
RP/0/0/CPU0:ios#
RP/0/0/CPU0:ios#rollback confi las 1
Fri Sep 20 20:43:22.253 UTC
Loading Rollback Changes.
Loaded Rollback Changes in 1 sec
Committing...RP/0/0/CPU0:Sep 20 20:43:25.932 : isis[285]: %ROUTING-ISIS-6-INFO_STARTUP_START : Cold controlled start beginning
.RP/0/0/CPU0:Sep 20 20:43:27.219 : ike[233]: %SECURITY-IKE-4-WARNING : You may want to configure a domain-name
.............RP/0/0/CPU0:Sep 20 20:43:39.838 : isis[285]: %ROUTING-ISIS-5-ADJCHANGE : Adjacency to 49.0001.0000.0000.0020 (GigabitEthernet0/1/0/0.1920) (L2) Up, New adjacency

49 items committed in 17 sec (2)items/sec
Updating.RP/0/0/CPU0:Sep 20 20:43:41.276 : config_rollback[65749]: %MGBL-CONFIG-6-DB_COMMIT : Configuration committed by user 'xr1'. Use 'show configuration commit changes 1000001332' to view the changes.

Updated Commit database in 1 sec
Configuration successfully rolled back 1 commits.
RP/0/0/CPU0:XR1#RP/0/0/CPU0:Sep 20 20:43:43.658 : bgp[139]: %ROUTING-BGP-5-ADJCHANGE : neighbor 12.1.19.1 Up (VRF: default)
RP/0/0/CPU0:Sep 20 20:43:44.003 : isis[285]: %ROUTING-ISIS-6-INFO_STARTUP_FINISH : Cold controlled start completed

RP/0/0/CPU0:XR1#
RP/0/0/CPU0:XR1#
RP/0/0/CPU0:XR1#
RP/0/0/CPU0:XR1#sho mpls for
Fri Sep 20 20:45:30.320 UTC
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes
Label  Label       or ID              Interface                    Switched
------ ----------- ------------------ ------------ --------------- ------------
16001  Pop         20.4.20.0/24       Gi0/1/0/0.1920 20.19.20.20     0         
16004  Pop         20.20.20.20/32     Gi0/1/0/0.1920 20.19.20.20     150       
16005  Pop         12.1.19.1/32       Gi0/1/0/0.119 12.1.19.1       107


#same labels

16006  20          2.2.2.2/32         Gi0/1/0/0.119 12.1.19.1       0
16007  19          5.5.5.5/32         Gi0/1/0/0.119 12.1.19.1       0

RP/0/0/CPU0:XR1#RP/0/0/CPU0:Sep 20 20:46:21.594 : isis[285]: %ROUTING-ISIS-5-ADJCHANGE : Adjacency to 49.0001.0000.0000.0004 (GigabitEthernet0/1/0/0.419) (L2) Up, New adjacency

But before the process restart this was the state on

R4

17         No Label   2.2.2.2/32       0             Fa0/0.419  20.4.19.19
18         No Label   5.5.5.5/32       0             Fa0/0.419  20.4.19.19

and XR2

16005  Unlabelled  5.5.5.5/32         Gi0/4/0/0.1920 20.19.20.19     0         
16006  Unlabelled  2.2.2.2/32         Gi0/4/0/0.1920 20.19.20.19     0

 

once XR1 had its config restored we see this on

R4

17         16006      2.2.2.2/32       5642          Fa0/0.419  20.4.19.19
18         16007      5.5.5.5/32       0             Fa0/0.419  20.4.19.19

XR2

16005  16007       5.5.5.5/32         Gi0/4/0/0.1920 20.19.20.19     1984      
16006  16006       2.2.2.2/32         Gi0/4/0/0.1920 20.19.20.19     0 

 

I haven't seen a problem like this before on XR and I've been runnig a GSR for about a year now. Have others seen this issue?  Im glad of course i found it now but I wasted 20minutes.  How long would you go 'that looks fine' before doing a commit replace?

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