Diagnosis and Troubleshoot

Network Diagnose & Troubleshoot

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Reachabiliy Diagnosis and Troubleshoot

  1. Check IPv4/IPv6 address of port and Port up/down status.
  2. ping each others physical interface
  3. Ping successful, check ping loopbacks(or advertised/ received prefixes)
  4. In case of Link State protocols, the link neiborship happens via link-local address(same IP address for IPv4 adjacencies whereas link-local FE:xx for IPv6 adjacencies), check for link-local address blocking.
  5. Area types(Level 1, Level 2, and Level 1-2) mismatch. NET areas mismatch. Network type(point-to-point, broadcast) mismatch.
  6. Topology mismatch(single, Multi).
  7. Wrong consideration while interconnecting different isis levels.
  8. ISIS metrics and metric-type mismatches.

 

Show Outputs

RP/0/0/CPU0:R7#sh isis neighbors
Sun Mar 24 16:53:21.928 UTC

IS-IS 20 neighbors:
System Id      Interface        SNPA           State Holdtime Type IETF-NSF
R8             Gi0/0/0/0        *PtoP*         Up    29       L1   Capable
R8             Gi0/0/0/1        *PtoP*         Up    29       L2   Capable
R11            Gi0/0/0/3        *PtoP*         Up    22       L2   Capable

Total neighbor count: 3
RP/0/0/CPU0:R7#


RP/0/0/CPU0:R7#sh isis database 
Sun Mar 24 16:56:46.474 UTC

IS-IS 20 (Level-1) Link State Database
LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime  ATT/P/OL
R7.00-00            * 0x0000000e   0xac76        1043            0/0/0
R8.00-00              0x00000012   0x73b9        653             0/0/0
R12.00-00             0x0000000f   0x418a        1152            0/0/0

 Total Level-1 LSP count: 3     Local Level-1 LSP count: 1

IS-IS 20 (Level-2) Link State Database
LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime  ATT/P/OL
R7.00-00            * 0x00000012   0xcf1f        1065            0/0/0
R8.00-00              0x00000013   0xed58        929             0/0/0
R11.00-00             0x0000000d   0xbb18        568             0/0/0

 Total Level-2 LSP count: 3     Local Level-2 LSP count: 1
RP/0/0/CPU0:R7#


RP/0/0/CPU0:R7#sh isis adjacency-log first 100
Sun Mar 24 16:57:39.960 UTC

   IS-IS 20 Level 1 Adjacency log
When          System          Interface          State   Details
--- Sun Mar 24 2019 ---
14:33:30.973  R8              Gi0/0/0/0          d -> i 
14:33:30.993  R8              Gi0/0/0/0          i -> u  New adjacency
                                                         IPv4 Unicast Up
                                                         IPv6 Unicast Up

   IS-IS 20 Level 2 Adjacency log
When          System          Interface          State   Details
--- Sun Mar 24 2019 ---
14:33:30.973  R8              Gi0/0/0/1          d -> i 
14:33:30.973  R11             Gi0/0/0/3          d -> i 
14:33:30.993  R8              Gi0/0/0/1          i -> u  New adjacency
                                                         IPv4 Unicast Up
                                                         IPv6 Unicast Up
14:33:31.003  R11             Gi0/0/0/3          i -> u  New adjacency
                                                         IPv4 Unicast Up
                                                         IPv6 Unicast Up
RP/0/0/CPU0:R7#



RP/0/0/CPU0:R7#sh isis topology summary
Sun Mar 24 17:00:14.080 UTC

IS-IS 20 IS Topology Summary IPv4 Unicast
                          L1                              L2
               Reach  UnReach   Total/All      Reach  UnReach  Total/All
                      In Top                          In Top
              ------- ------- -------------   ------- ------- -------------
Router nodes:       3       0      3/3              2       1      3/3    
Pseudo nodes:       0       0      0/0              0       0      0/0    

 Total nodes:       3       0      3/3              2       1      3/3    
RP/0/0/CPU0:R7#



RP/0/0/CPU0:R7#sh isis error-log
Sun Mar 24 17:01:37.384 UTC

   IS-IS 20 Error Log
When          Log Level  Err String Err Code   Details                         
RP/0/0/CPU0:R7#



RP/0/0/CPU0:R7#sh isis afi-all safi-all fast-reroute
Sun Mar 24 17:06:34.244 UTC

IS-IS 20 IPv4 Unicast FRR backups

Codes: L1 - level 1, L2 - level 2, ia - interarea (leaked into level 1)
       df - level 1 default (closest attached router), su - summary null
       C - connected, S - static, R - RIP, B - BGP, O - OSPF
       E - EIGRP, A - access/subscriber, M - mobile, a - application
       i - IS-IS (redistributed from another instance)
       D - Downstream, LC - Line card disjoint, NP - Node protecting
       P - Primary path, SRLG - SRLG disjoint, TM - Total metric via backup

Maximum parallel path count: 8

C  20.0.0.7/32
     is directly connected, Loopback0
   L2 RIB backup [20/115]
     via 20.77.8.8, GigabitEthernet0/0/0/1, R8, Weight: 0
       No FRR backup
L1 20.0.0.8/32 [10/115]
     via 20.7.8.8, GigabitEthernet0/0/0/0, R8, Weight: 0
       No FRR backup
L1 20.0.0.12/32 [20/115]
     via 20.7.8.8, GigabitEthernet0/0/0/0, R8, Weight: 0
       No FRR backup
L1 20.7.8.0/24 [20/115]
     via 20.7.8.8, GigabitEthernet0/0/0/0, R8, Weight: 0
       No FRR backup
L1 20.8.12.0/24 [20/115]
     via 20.7.8.8, GigabitEthernet0/0/0/0, R8, Weight: 0
       No FRR backup
L2 20.77.8.0/24 [20/115]
     via 20.77.8.8, GigabitEthernet0/0/0/1, R8, Weight: 0
       No FRR backup

IS-IS 20 IPv6 Unicast FRR backups

Codes: L1 - level 1, L2 - level 2, ia - interarea (leaked into level 1)
       df - level 1 default (closest attached router), su - summary null
       C - connected, S - static, R - RIP, B - BGP, O - OSPF
       E - EIGRP, A - access/subscriber, M - mobile, a - application
       i - IS-IS (redistributed from another instance)
       D - Downstream, LC - Line card disjoint, NP - Node protecting
       P - Primary path, SRLG - SRLG disjoint, TM - Total metric via backup

Maximum parallel path count: 8

C  2012:20::7/128
     is directly connected, Loopback0
   L2 RIB backup [20/115]
     via fe80::8, GigabitEthernet0/0/0/1, R8, Weight: 0
       No FRR backup
L1 2012:20::8/128 [10/115]
     via fe80::8, GigabitEthernet0/0/0/0, R8, Weight: 0
       No FRR backup
L1 2012:20::12/128 [20/115]
     via fe80::8, GigabitEthernet0/0/0/0, R8, Weight: 0
       No FRR backup
RP/0/0/CPU0:R7#



RP/0/0/CPU0:R7#sh isis protocol
Sun Mar 24 17:12:23.040 UTC

IS-IS Router: 20
  System Id: 0020.2000.0007
  IS Levels: level-1-2
  Manual area address(es):
    49
  Routing for area address(es):
    49
  Non-stop forwarding: Disabled
  Most recent startup mode: Cold Restart
  Topologies supported by IS-IS:
    IPv4 Unicast
      Level-1
        Metric style (generate/accept): Wide/Wide
        Metric: 10
        ISPF status: Disabled
      Level-2
        Metric style (generate/accept): Wide/Wide
        Metric: 10
        ISPF status: Disabled
      No protocols redistributed
      Distance: 115
      Advertise Passive Interface Prefixes Only: Yes
    IPv6 Unicast
      Level-1
        Metric: 10
        ISPF status: Disabled
      Level-2
        Metric: 10
        ISPF status: Disabled
      No protocols redistributed
      Distance: 115
      Advertise Passive Interface Prefixes Only: Yes
  Interfaces supported by IS-IS:
    Loopback0 is running passively (passive in configuration)
    GigabitEthernet0/0/0/0 is running suppressed (active in configuration)
    GigabitEthernet0/0/0/1 is running suppressed (active in configuration)
    GigabitEthernet0/0/0/3 is running suppressed (active in configuration)
RP/0/0/CPU0:R7#


R11#sh isis * topology

Tag 20:

IS-IS TID 0 paths to level-2 routers
System Id            Metric     Next-Hop             Interface   SNPA
R7                   10         R7                   Et0/0       5000.0007.0004
R8                   20         R7                   Et0/0       5000.0007.0004
R11                  --


IS-IS TID 2 paths to level-2 routers
System Id            Metric     Next-Hop             Interface   SNPA
R7                   10         R7                   Et0/0       5000.0007.0004
R8                   20         R7                   Et0/0       5000.0007.0004
R11                  --
R11#

R11#sh isis * rib


IPv4 local RIB for IS-IS process 20

IPV4 unicast topology base (TID 0, TOPOID 0x0) =================

20.0.0.7/32
  [115/L2/10] via 20.7.11.7(Ethernet0/0), from 20.0.0.7, tag 0, LSP[2/17]
              (installed)
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.8, tag 0, LSP[4/2]

20.0.0.8/32
  [115/L2/20] via 20.7.11.7(Ethernet0/0), from 20.0.0.7, tag 0, LSP[2/17]
              (installed)
  [115/L2/20] via 20.7.11.7(Ethernet0/0), from 20.0.0.8, tag 0, LSP[4/2]

20.0.0.12/32
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.7, tag 0, LSP[2/17]
              (installed)
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.8, tag 0, LSP[4/2]

20.7.8.0/24
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.7, tag 0, LSP[2/17]
              (installed)
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.8, tag 0, LSP[4/2]
         
20.8.12.0/24
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.7, tag 0, LSP[2/17]
              (installed)
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.8, tag 0, LSP[4/2]
         
20.77.8.0/24
  [115/L2/30] via 20.7.11.7(Ethernet0/0), from 20.0.0.8, tag 0, LSP[4/2]
              (installed)
IS-IS IPv6 process 20, local RIB
* 2012:20::7/128
    via FE80::7/Ethernet0/0, type L2  metric 10 tag 0 LSP [2/11]
    via FE80::7/Ethernet0/0, type L2  metric 30 tag 0 LSP [4/2]
* 2012:20::8/128
    via FE80::7/Ethernet0/0, type L2  metric 20 tag 0 LSP [2/11]
    via FE80::7/Ethernet0/0, type L2  metric 20 tag 0 LSP [4/2]
* 2012:20::12/128
    via FE80::7/Ethernet0/0, type L2  metric 30 tag 0 LSP [2/11]
    via FE80::7/Ethernet0/0, type L2  metric 30 tag 0 LSP [4/2]
R11#


R11#sh isis database

Tag 20:
IS-IS Level-2 Link State Database:
LSPID                 LSP Seq Num  LSP Checksum  LSP Holdtime      ATT/P/OL
R7.00-00              0x00000017   0xC524        1092              0/0/0
R8.00-00              0x00000016   0xE75B        1051              0/0/0
R11.00-00           * 0x00000011   0xB31C        1092              0/0/0
R11#                 


R11#sh isis neighbors

Tag 20:
System Id      Type Interface   IP Address      State Holdtime Circuit Id
R7             L2   Et0/0       20.7.11.7       UP    24       00
R11
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