Reachabiliy Diagnosis and Troubleshoot
- Check IPv4/IPv6 address of port and Port up/down status.
- ping each others physical interface
- Ping successful, check ping loopbacks(or advertised/ received prefixes)
- 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.
- Area types(Level 1, Level 2, and Level 1-2) mismatch. NET areas mismatch. Network type(point-to-point, broadcast) mismatch.
- Topology mismatch(single, Multi).
- Wrong consideration while interconnecting different isis levels.
- 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#
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#
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#
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
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
14:33:31.003 R11 Gi0/0/0/3 i -> u New adjacency
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#
Sun Mar 24 17:00:14.080 UTC
IS-IS 20 IS Topology Summary IPv4 Unicast
L1
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#
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#
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#
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#
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#
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#
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
Tag 20:
System Id Type Interface IP Address State Holdtime Circuit Id
R7 L2 Et0/0 20.7.11.7 UP 24 00
R11