Troubleshoot IS-IS Adjacency Issues
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Introduction
This document describes how to troubleshoot IS-IS protocol for Cisco IOS® XE platforms.
Prerequisites
Requirements
Cisco recommends that you have knowledge of these topics:
- Intermediate System to Intermediate System (IS-IS)
- Cisco IOS XE
For more information on these topics, see:
Components Used
The information in this document is based on Cisco IOS XE software.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.
IS-IS Adjacency Down
This section provides a solution to the common problem of IS-IS down. This network diagram is used as an example:
Baseline Topology
IS-IS is down between DeviceA and DeviceB.
DeviceA#show isis neighbors detail System Id Type Interface IP Address State Holdtime Circuit Id DeviceA#
DeviceB#show isis neighbors detail System Id Type Interface IP Address State Holdtime Circuit Id DeviceA L1L2 Twe1/0/9 192.0.2.1 DOWN 28 05 Area Address(es): 49.0001 SNPA: a84f.b1c3.9484 State Changed: never Format: Phase V Remote TID: 0 Local TID: 0 Interface name: TwentyFiveGigE1/0/9 Neighbor Circuit Id: 5 Adj sync: Full
Diagnose the Problem:
1. Validate the connectivity between the devices.
DeviceA#ping 192.0.2.2 size 1500 df-bit Type escape sequence to abort. Sending 5, 1500-byte ICMP Echos to 192.0.2.2, timeout is 2 seconds: Packet sent with the DF bit set !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms DeviceA#
DeviceB#ping 192.0.2.1 size 1500 df-bit Type escape sequence to abort. Sending 5, 1500-byte ICMP Echos to 192.0.2.1, timeout is 2 seconds: Packet sent with the DF bit set !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms DeviceB#
2. Review the configuration on both sides.
DeviceA#show running-config | sec router isis ip router isis router isis net 49.0001.0000.0000.000a.00 DeviceA#
DeviceB#show running-config | sec router isis ip router isis router isis net 49.0001.0000.0000.000b.00 DeviceB#
3. Validate if the adjacency is up at the Connectionless Network Service (CLNS). This provides a summary of the neighbors connected to your device.
DeviceA#show clns neighbors detail System Id Interface SNPA State Holdtime Type Protocol 0000.0000.000B Te0/0/4 6c31.0edb.3b5f Up 257 IS ES-IS Area Address(es): 49.0001 Uptime: 02:02:11 Interface name: TenGigabitEthernet0/0/4 DeviceA#
DeviceB#show clns neighbors detail System Id Interface SNPA State Holdtime Type Protocol 0000.0000.000A Twe1/0/9 a84f.b1c3.9484 Down 20 L1L2 IS-IS Area Address(es): 49.0001 IP Address(es): 192.0.2.1* Uptime: 02:02:09 NSF capable Interface name: TwentyFiveGigE1/0/9 DeviceB#
The mac-addresses listed on each CLNS neighbor are the mac addresses of the remote devices which peer with the local device.
DeviceA#show interface TenGigabitEthernet0/0/4
TenGigabitEthernet0/0/4 is up, line protocol is up
Hardware is 8xSFP+, address is a84f.b1c3.9484 (bia a84f.b1c3.9484) < mac address appeared on SNPA DeviceB
Internet address is 192.0.2.1/30
MTU 1500 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255 DeviceB#show interface TwentyFiveGigE1/0/9
TwentyFiveGigE1/0/9 is up, line protocol is up (connected)
Hardware is Twenty Five Gigabit Ethernet, address is 6c31.0edb.3b5f (bia 6c31.0edb.3b5f) < mac address appeared on SNPA DeviceA
Internet address is 192.0.2.2/30
MTU 9216 bytes, BW 10000000 Kbit/sec, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set4. Run the command show clns interface <interface> in order to validate if the parameters match with the peer.
Ensure to match these values:
- Maximum Transmission Unit (MTU)
- Circuit Type
| DeviceA |
DeviceA#show clns interface TenGigabitEthernet0/0/4 |
| DeviceB |
DeviceB#show clns interface TwentyFiveGigE1/0/9 |
In this scenario, the problem is related to the MTU mismatch. If the remote peer is not accessible, the debug isis adj-packets <interface> can show the MTU value being sent and received.
Note: This applies only when the command show clns interfaceprints if state INIT.
DeviceA#debug isis adj-packets TenGigabitEthernet 0/0/4
IS-IS Adjacency related packets debugging is on for router process null
*Jul 18 23:24:16.598: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5
*Jul 18 23:24:16.599: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 < MTU sent to the neighbor >
*Jul 18 23:24:25.189: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5
*Jul 18 23:24:25.189: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496
*Jul 18 23:24:34.057: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5
*Jul 18 23:24:34.057: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496
*Jul 18 23:24:42.866: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5
*Jul 18 23:24:42.866: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496
*Jul 18 23:24:51.646: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5
*Jul 18 23:24:51.646: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496
*Jul 18 23:24:59.606: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5
*Jul 18 23:24:59.606: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496
DeviceB#debug isis adj-packets twentyFiveGigE 1/0/9
*Jul 18 23:53:22.420: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:INIT, length 9212 < MTU sent to the neighbor >
*Jul 18 23:53:22.591: ISIS-Adj: Rec serial IIH from a84f.b1c3.9484 (TwentyFiveGigE1/0/9)
*Jul 18 23:53:22.591: ISIS-Adj: cir type L1L2, cir id 05, length 1496 < MTU received from neighbor >
*Jul 18 23:53:22.592: ISIS-Adj: rcvd state DOWN, old state INIT, new state INIT, nbr usable TRUE
*Jul 18 23:53:22.592: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x49000184 Length:5
*Jul 18 23:53:22.592: ISIS-Adj: Nghbr Ckt ID changed: FALSE
*Jul 18 23:53:22.592: ISIS-Adj: newstate:1, state_changed:0, going_up:0, going_down:0
*Jul 18 23:53:22.592: ISIS-Adj: Action = ACCEPT
*Jul 18 23:53:22.592: ISIS-Adj: ACTION_ACCEPT:
...
ISIS Adjacency Down (Not MTU Mismatch Related)
IS-IS is down and MTU matches on the interfaces.
DeviceA#show clns neighbors System Id Interface SNPA State Holdtime Type Protocol DeviceA#
DeviceB#show clns neighbors System Id Interface SNPA State Holdtime Type Protocol DeviceB#
- Validate the configuration that is matching with the peer.
- Ensure that the physical interface is in a good condition to transmit (no errors or light levels problem).
- Check connectivity between peers (ping test adding the MTU size and the df-bit).
- Validate the CLNS neighbors between the peers.
- Ensure that both ends have the same MTU and same Circuit-Type along with the state.
| DeviceA |
DeviceA#show clns interface TenGigabitEthernet 0/0/4 |
| DeviceB |
DeviceB#show clns interface twentyFiveGigE 1/0/9 |
6. Enable debug isis adj-packet <interface> and validate the packets that are sent and received.
DeviceA#debug isis adj-packets TenGigabitEthernet 0/0/4
IS-IS Adjacency related packets debugging is on for router process null *Jul 19 13:32:52.788: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5 *Jul 19 13:32:52.788: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 *Jul 19 13:33:00.708: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5 *Jul 19 13:33:00.709: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 *Jul 19 13:33:09.726: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5 *Jul 19 13:33:09.726: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 *Jul 19 13:33:18.376: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5 *Jul 19 13:33:18.376: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 *Jul 19 13:33:26.132: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5 *Jul 19 13:33:26.132: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 DeviceA#
DeviceB#debug isis adj-packets TwentyFiveGigE1/0/9 IS-IS Adjacency related packets debugging is on for router process null *Jul 19 14:01:32.125: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x0 Length:5 *Jul 19 14:01:32.125: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:DOWN, length 1496 *Jul 19 14:01:40.005: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x0 Length:5 *Jul 19 14:01:40.005: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:DOWN, length 1496 *Jul 19 14:01:49.602: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x0 Length:5 *Jul 19 14:01:49.602: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:DOWN, length 1496 *Jul 19 14:01:58.284: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x0 Length:5 *Jul 19 14:01:58.284: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:DOWN, length 1496
Both devices are sending, but they do not receive the Hello Packet from their neighbors.
7. Enable a capture in order to validate that the packets are sent to each neighbor. Once the capture is complete, export it to the bootflash or flash as a.pcap file
DeviceA#show monitor cap cap parameter
monitor capture cap interface TenGigabitEthernet0/0/4 BOTH < Interface from where send and receive the Hello Packets >
monitor capture cap control-plane IN < Packets to be process and generated by the CPU >
monitor capture cap access-list TAC < ACL for capture only the IS-IS packets >
monitor capture cap buffer size 10
monitor capture cap limit pps 1000
DeviceA#show access-list TAC
Extended MAC access list TAC
permit host a84f.b1c3.9484 host 0900.2b00.0005 < Local MAC address towards the IS-IS Hello >
permit host 6c31.0edb.3b5f host 0900.2b00.0005 < Remote MAC address towards the IS-IS Hello >DeviceB#show monitor capture cap parameter monitor capture cap interface TwentyFiveGigE1/0/9 BOTH < Interface from where send and receive the Hello Packets > monitor capture cap control-plane BOTH < Packets to be process and generated by the CPU > monitor capture cap match any < match all the packets on the switch > monitor capture cap buffer size 10
Note: EPC at Catalyst Cisco IOS XE switches only captures outgoing IS-IS hellos and not the ingress packets. As an alternative, SPAN captures are recommended.
Reference to the Hello Packets is shown in this table.
| Name | Destination Mac address |
| All L1 ISs | 0180.c200.0014 |
| All L2 ISs | 0180.c200.0015 |
| All ISs | 0900.2b00.0005 |
| All ESs | 0900.2b00.0004 |
8. Review the exported capture and ensure that the hello packets are exchanged between neighbors.
DeviceA sends the hello packets adding their system ID (red square). It is expected to receive a packet from its neighbor with its system ID. In this capture, you can appreciate that DeviceB does not forward these packets to the peer.
DeviceA ISIS Down Capture
DeviceB capture shows that the hello packets are sent to its neighbor (red square). However, similar to the last capture, it does not receive the Hello packets from its neighbor.
DeviceB ISIS Down Capture
The problem in this scenario is due to an intermediate device that does not allow to send the hello packets. If you observe a similar situation and need to troubleshoot further, open a Cisco TAC Case.
IS-IS Adjacency Unstable
This section provides a solution to the common problem of IS-IS flaps.
Diagnose the Problem:
IS-IS is unstable between DeviceA and DeviceB.
DeviceA#show logging
Jul 19 15:05:03.623: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired
Jul 19 15:05:15.075: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Up, new adjacency
Jul 19 15:07:04.575: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired
Jul 19 15:07:15.759: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Up, new adjacency
Jul 19 15:09:04.983: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired
Jul 19 15:09:14.835: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Up, new adjacency
DeviceB#show logging
Jul 19 15:05:02.316: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired
Jul 19 15:05:18.191: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Up, new adjacency
Jul 19 15:07:09.280: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired
Jul 19 15:07:18.876: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Up, new adjacency
Jul 19 15:09:06.080: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired!
Jul 19 15:09:17.948: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Up, new adjacency
1. Check connectivity between peers (ping test with MTU size and the df-bit set).
2. Ensure that the physical interface is in a good condition to transmit (no errors or light levels problem).
3. Validate the CLNS neighbors send traffic to each other with the command show clns traffic interface <interface>.
DeviceA#show clns traffic interface TenGigabitEthernet0/0/4 CLNS: Time since last clear: 00:01:57 CLNS & ESIS Output: 3, Input: 21 Dropped Protocol not enabled on interface: 0 CLNS Local: 0, Forward: 0
<snip>
Interface TenGigabitEthernet0/0/4: IS-IS: Time since last clear: 00:01:57 IS-IS: Level-1 Hellos (sent/rcvd): 0/0 IS-IS: Level-2 Hellos (sent/rcvd): 0/0 IS-IS: PTP Hellos (sent/rcvd): 15/11 < DeviceA sends hello packets and receives less than its sends> IS-IS: Level-1 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-2 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-1 CSNPs (sent/rcvd): 1/1 IS-IS: Level-2 CSNPs (sent/rcvd): 1/1 IS-IS: Level-1 PSNPs (sent/rcvd): 1/1 IS-IS: Level-2 PSNPs (sent/rcvd): 1/1 IS-IS: Level-1 DR Elections: 0 IS-IS: Level-2 DR Elections: 0
DeviceB#show clns traffic interface TwentyFiveGigE1/0/9 CLNS: Time since last clear: 00:00:27 CLNS queue depth: 0/100, drops: 0, highest: 2 CLNS & ESIS Output: 1, Input: 14 Dropped Protocol not enabled on interface: 0 CLNS Local: 0, Forward: 0 <snip> Interface TwentyFiveGigE1/0/9: IS-IS: Time since last clear: 00:00:27 IS-IS: Level-1 Hellos (sent/rcvd): 0/0 IS-IS: Level-2 Hellos (sent/rcvd): 0/0 IS-IS: PTP Hellos (sent/rcvd): 4/5 < DeviceB, sends and receives a couple of hellos in comparison with DeviceA> IS-IS: Level-1 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-2 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-1 CSNPs (sent/rcvd): 1/1 IS-IS: Level-2 CSNPs (sent/rcvd): 1/1 IS-IS: Level-1 PSNPs (sent/rcvd): 1/1 IS-IS: Level-2 PSNPs (sent/rcvd): 1/1 IS-IS: Level-1 DR Elections: 0 IS-IS: Level-2 DR Elections: 0
Tip: The command clns traffic displays the IS-IS Hellos based on the IS-IS Level and IS-IS network type.
4. Enable debug ISIS adj-packets <interface>in order to see which packets are exchanged between neighbors.
DeviceA#show isis adj-packets TenGigabitEthernet0/0/4 < Hellos sent to the DeviceB with no response > Jul 19 18:58:34.779: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 19 18:58:34.779: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 19 18:58:42.719: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 19 18:58:42.719: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 19 18:58:50.430: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 19 18:58:50.430: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 19 18:58:58.356: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 19 18:58:58.356: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 < IS-IS declares the protocol down > Jul 19 18:59:01.879: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired < IS-IS sends hellos to the neighbor and receives a response from DeviceB > Jul 19 18:59:01.879: ISIS-Adj: L2 adj count 0 Jul 19 18:59:07.724: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5 Jul 19 18:59:07.724: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 Jul 19 18:59:15.894: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x0 Length:5 Jul 19 18:59:15.894: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:DOWN, length 1496 Jul 19 18:59:15.896: ISIS-Adj: Rec serial IIH from 6c31.0edb.3b5f (TenGigabitEthernet0/0/4) Jul 19 18:59:15.896: ISIS-Adj: cir type L2, cir id 0B, length 1496 Jul 19 18:59:15.896: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15 Jul 19 18:59:15.896: ISIS-Adj: Nghbr Ckt ID changed: TRUE Jul 19 18:59:15.896: ISIS-Adj: received Neighbor System-ID (must be our) 0000.0000.000A Jul 19 18:59:15.896: ISIS-Adj: received Neighbor ext.circuit ID (must be our) 0x5 Jul 19 18:59:15.896: ISIS-Adj: newstate:1, state_changed:1, going_up:0, going_down:0 Jul 19 18:59:15.896: ISIS-Adj: Action = GOING UP, new type = L2 < DeviceA declares that the adjacency is UP and starts to establish the session > Jul 19 18:59:15.896: ISIS-Adj: New serial adjacency Jul 19 18:59:15.896: ISIS-Adj: rcvd state INIT, old state DOWN, new state INIT, nbr usable TRUE Jul 19 18:59:15.898: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 19 18:59:15.898: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:INIT, length 1496 Jul 19 18:59:15.900: ISIS-Adj: Rec serial IIH from 6c31.0edb.3b5f (TenGigabitEthernet0/0/4) Jul 19 18:59:15.900: ISIS-Adj: cir type L2, cir id 0B, length 1496 Jul 19 18:59:15.900: ISIS-Adj: rcvd state UP, old state INIT, new state UP, nbr usable TRUE Jul 19 18:59:15.900: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15 Jul 19 18:59:15.900: ISIS-Adj: Nghbr Ckt ID changed: FALSE Jul 19 18:59:15.900: ISIS-Adj: received Neighbor System-ID (must be our) 0000.0000.000A Jul 19 18:59:15.900: ISIS-Adj: received Neighbor ext.circuit ID (must be our) 0x5 Jul 19 18:59:15.900: ISIS-Adj: newstate:0, state_changed:1, going_up:1, going_down:0 Jul 19 18:59:15.900: ISIS-Adj: Action = GOING UP, new type = L2 Jul 19 18:59:15.900: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Up, new adjacency
DeviceB#debug isis adj-packets TwentyFiveGigE1/0/9 < Hello sent to the DeviceA with no response > Jul 19 18:58:44.105: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15 Jul 19 18:58:44.105: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496 Jul 19 18:58:51.814: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15 Jul 19 18:58:51.814: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496 Jul 19 18:58:59.768: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15 Jul 19 18:58:59.768: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496 < IS-IS declares the protocol down > Jul 19 18:59:07.886: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired
< IS-IS sends hellos to the neighbor and receives a response from DeviceA >
Jul 19 18:59:07.887: ISIS-Adj: L2 adj count 0 Jul 19 18:59:08.422: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x0 Length:5 Jul 19 18:59:08.422: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:DOWN, length 1496 Jul 19 18:59:16.144: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x0 Length:5 Jul 19 18:59:16.144: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:DOWN, length 1496 Jul 19 18:59:19.001: ISIS-Adj: Rec serial IIH from a84f.b1c3.9484 (TwentyFiveGigE1/0/9) Jul 19 18:59:19.001: ISIS-Adj: cir type L2, cir id 05, length 1496 Jul 19 18:59:19.001: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0x49000184 Length:5 Jul 19 18:59:19.001: ISIS-Adj: Nghbr Ckt ID changed: TRUE Jul 19 18:59:19.001: ISIS-Adj: newstate:1, state_changed:1, going_up:0, going_down:0 Jul 19 18:59:19.001: ISIS-Adj: Action = GOING UP, new type = L2 < DeviceB declares that the adjacency is UP and starts to establish the session > Jul 19 18:59:19.001: ISIS-Adj: New serial adjacency Jul 19 18:59:19.001: ISIS-Adj: rcvd state DOWN, old state DOWN, new state INIT, nbr usable TRUE Jul 19 18:59:19.002: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15 Jul 19 18:59:19.002: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:INIT, length 1496 Jul 19 18:59:19.004: ISIS-Adj: Rec serial IIH from a84f.b1c3.9484 (TwentyFiveGigE1/0/9) Jul 19 18:59:19.004: ISIS-Adj: cir type L2, cir id 05, length 1496 Jul 19 18:59:19.004: ISIS-Adj: rcvd state INIT, old state INIT, new state UP, nbr usable TRUE Jul 19 18:59:19.004: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 19 18:59:19.004: ISIS-Adj: Nghbr Ckt ID changed: FALSE Jul 19 18:59:19.004: ISIS-Adj: received Neighbor System-ID (must be our) 0000.0000.000B Jul 19 18:59:19.004: ISIS-Adj: received Neighbor ext.circuit ID (must be our) 0xB Jul 19 18:59:19.004: ISIS-Adj: newstate:0, state_changed:1, going_up:1, going_down:0 Jul 19 18:59:19.004: ISIS-Adj: Action = GOING UP, new type = L2 Jul 19 18:59:19.004: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Up, new adjacency
5. Enable a capture in order to validate that the packets are sent to each neighbor. Once the capture is complete, export the capture to the bootflash as a .pcap file and upload it to a TFTP server for more details.
DeviceA receives a packet from DeviceB (19:15.05) after this packet is received. DeviceA sends its corresponding hello without any reply from the neighbor until it reaches the hold time expired which is 30 seconds by default (red square).
This is when this router declares the adjacency down. After this period, DeviceB sends its hello and is received by DeviceA and these packets are exchanged with no problem (green square).
ISIS unstable DeviceA
Capture from DeviceB is similar to the symptom from the peer. The device does not receive the hello packets from its neighbor. The last packet is sent from DeviceB with no reply from DeviceA until it reaches the 30 seconds hold timer. This switch considers the adjacency down. After this failure, the switch receives the hello from DeviceA and starts the neighborship.
ISIS Unstable DeviceB
This concludes there is a problem with the transport and you must review why the packets are being lost.
IS-IS Adjacency Unstable (Random Flaps)
IS-IS is unstable between DeviceA and DeviceB. The protocol encounters random flaps.
DeviceA#show logging Jul 21 10:03:38.633: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired Jul 21 10:05:10.272: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Up, new adjacency Jul 21 10:33:41.528: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired Jul 21 10:35:07.979: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Up, new adjacency Jul 21 11:03:42.442: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired Jul 21 11:05:08.469: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Up, new adjacency
DeviceB#show logging Jul 21 10:03:44.535: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired Jul 21 10:05:13.281: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Up, new adjacency Jul 21 10:33:38.408: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired Jul 21 10:35:10.989: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Up, new adjacency Jul 21 11:03:39.291: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired Jul 21 11:05:11.479: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Up, new adjacency
When the problem occurs, ensure to proceed with these actions:
- Validate that the configuration matches with the peer.
- Ensure that the physical interface is in a good condition to transmit (no errors or light levels problem).
- Check connectivity between peers (ping test with MTU size and the df-bit set).
Tip: It is not easy to troubleshoot these kinds of issues due to the condition of the random flaps. In order to tackle this situation, consider using scripts to run the necessary commands and continue to troubleshoot.
4. Proceed to configure a monitor capture with an Access-list in order to be more specific on the troubleshooting.
5. Disable the logging console and enable the debug isis adj-packets <interface>.
DeviceA(config)#no logging console DeviceA(config)#exit DeviceA#debug isis adj-packets TenGigabitEthernet0/0/4
6. Enable the packet capture on the equipment and activate it.
DeviceA#show monitor capture cap parameter
monitor capture cap interface TenGigabitEthernet0/0/4 BOTH monitor capture cap control-plane IN monitor capture cap access-list TAC > match only the packets allowed on the ACL monitor capture cap buffer size 100 circular > when the capture reaches the size of 100 MB this overwrite the previous information. monitor capture cap limit pps 1000
DeviceA#show access-lists TAC Extended MAC access list TAC permit host a84f.b1c3.9484 host 0900.2b00.0005 < Local MAC address towards the IS-IS Hello > permit host 6c31.0edb.3b5f host 0900.2b00.0005 < Remote MAC address towards the IS-IS Hello >
DeviceA#monitor capture cap start
7. Configure the Embedded Event Manager (EEM) on the Cisco device. Once the issue triggers the syslog pattern, this generates logs that are stored on the flash as a .txt file. Proceed to upload them to a TFTP server for more information.
DeviceA#show running-config | sec event event manager applet ISIS_Flap authorization bypass
event syslog pattern "%CLNS-5-ADJCHANGE:.*hold time expired"
action 1.0 syslog msg "ISIS down Please wait - capturing the traffic"
action 1.1 cli command "enable"
action 1.2 cli command "show clns interface ten0/0/4 | append bootflash:ISIS_DeviceA.txt"
action 1.3 cli command "show clns traffic interface tenGigabitEthernet 0/0/4 | append bootflash:ISIS_DeviceA.txt"
action 2.0 cli command "show logging | append bootflash:debug_DeviceA.txt"
action 2.1 cli command "undebug all"
action 2.2 cli command "monitor capture cap stop"
action 3.0 cli command "end"
For switches to append the logs it is neccesary to use the append flash:<document.txt> , as example:
event manager applet ISIS_Flap authorization bypass event syslog pattern "%CLNS-5-ADJCHANGE:.*hold time expired" action 1.0 syslog msg "ISIS down Please wait - capturing the traffic" action 1.1 cli command "enable" action 1.2 cli command "show clns interface ten0/0/4 | append flash:ISIS_DeviceB.txt"
<snip>
action 3.0 cli command "end"
8. Once the issue triggers, proceed to export the capture on the bootflash/flash and ensure that the .txt files are stored properly in the same location.
DeviceA#monitor capture cap export bootflash:ISIS_DeviceA.pcap Exported Successfully DeviceA#dir bootflash:*.txt Directory of bootflash:/*.txt Directory of bootflash:/ 19 -rw- 6048 Jul 22 2023 13:33:40 +00:00 ISIS_DeviceA.txt 20 -rw- 103153 Jul 22 2023 13:33:40 +00:00 debug_DeviceA.txt 26975526912 bytes total (20527607808 bytes free)
DeviceB#monitor capture cap export location flash:ISIS_DeviceB.pcap
Exported Successfully
DeviceB#dir bootflash:*.txt Directory of bootflash:/*.txt Directory of bootflash:/ 356939 -rw- 660 Jul 22 2023 13:33:42 +00:00 ISIS_DeviceB.txt 356943 -rw- 103283 Jul 22 2023 13:33:42 +00:00 debug_DeviceB.txt
9. Upload the files to a TFTP server in order to compare the logs between devices.
DeviceA#copy bootflash:ISIS_DeviceA.txt tftp: Address or name of remote host []? < TFTP IP address > Destination filename [ISIS_DeviceA.txt]? <This name appears on the TFTP server> !! 18144 bytes copied in 0.095 secs (190989 bytes/sec)
10. Compare the captures and logs in order to validate if the packets are sent and received from both routers.
Analysis of the IS-IS logs:
- Both IS-IS interfaces are configured with the same network type L1-L2.
- The Interfaces state (if state DOWN) shows that both interfaces do not receive the hello packet.
- IS-IS: PTP Hellos has a mismatch in the packets sent and received. While DeviceA sends 205 packets and receives 199 from the peer, DeviceB has 202 out of 202. This indicates that the transport is not reliable.
DeviceA
TenGigabitEthernet0/0/4 is up, line protocol is up Attached to: isis Checksums enabled, MTU 1497, Encapsulation SAP ERPDUs enabled, min. interval 10 msec. CLNS fast switching disabled CLNS SSE switching disabled DEC compatibility mode OFF for this interface Next ESH/ISH in 30 seconds Routing Protocol: IS-IS Circuit Type: level-1-2 Interface number 0x0, local circuit ID 0x5 Neighbor Extended Local Circuit ID: 0x0 Level-1 Metric: 10, Priority: 64, Circuit ID: DeviceA.05 Level-1 IPv6 Metric: 10 Number of active level-1 adjacencies: 0 Level-2 Metric: 10, Priority: 64, Circuit ID: DeviceA.05 Level-2 IPv6 Metric: 10 Number of active level-2 adjacencies: 0 Next IS-IS Hello in 574 milliseconds if state DOWN CLNS: Time since last clear: 00:29:37 CLNS & ESIS Output: 33, Input: 241 Dropped Protocol not enabled on interface: 0 CLNS Local: 0, Forward: 0
<snip>
Interface TenGigabitEthernet0/0/4: IS-IS: Time since last clear: 00:29:37 IS-IS: Level-1 Hellos (sent/rcvd): 0/0 IS-IS: Level-2 Hellos (sent/rcvd): 0/0 IS-IS: PTP Hellos (sent/rcvd): 205/199 IS-IS: Level-1 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-2 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-1 CSNPs (sent/rcvd): 0/0 IS-IS: Level-2 CSNPs (sent/rcvd): 0/0 IS-IS: Level-1 PSNPs (sent/rcvd): 2/2 IS-IS: Level-2 PSNPs (sent/rcvd): 2/2 IS-IS: Level-1 DR Elections: 0 IS-IS: Level-2 DR Elections: 0 DeviceB TwentyFiveGigE1/0/9 is up, line protocol is up Attached to: isis Checksums enabled, MTU 1497, Encapsulation SAP ERPDUs enabled, min. interval 10 msec. CLNS fast switching disabled CLNS SSE switching disabled DEC compatibility mode OFF for this interface Next ESH/ISH in 20 seconds Routing Protocol: IS-IS Circuit Type: level-1-2 Interface number 0x0, local circuit ID 0xB Neighbor Extended Local Circuit ID: 0x0 P2P retransmit queue size: 0 Level-1 Metric: 10, Priority: 64, Circuit ID: DeviceB.0B Level-1 IPv6 Metric: 10 Number of active level-1 adjacencies: 0 Level-2 Metric: 10, Priority: 64, Circuit ID: DeviceB.0B Level-2 IPv6 Metric: 10 Number of active level-2 adjacencies: 0 Next IS-IS Hello in 7 seconds if state DOWN CLNS: Time since last clear: 00:29:34 CLNS queue depth: 0/100, drops: 0, highest: 1 CLNS & ESIS Output: 34, Input: 243 Dropped Protocol not enabled on interface: 0 CLNS Local: 0, Forward: 0 <snip> Interface TwentyFiveGigE1/0/9: IS-IS: Time since last clear: 00:29:34 IS-IS: Level-1 Hellos (sent/rcvd): 0/0 IS-IS: Level-2 Hellos (sent/rcvd): 0/0 IS-IS: PTP Hellos (sent/rcvd): 202/202 IS-IS: Level-1 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-2 LSPs flooded (sent/rcvd): 2/2 IS-IS: Level-1 CSNPs (sent/rcvd): 0/0 IS-IS: Level-2 CSNPs (sent/rcvd): 0/0 IS-IS: Level-1 PSNPs (sent/rcvd): 2/2 IS-IS: Level-2 PSNPs (sent/rcvd): 2/2 IS-IS: Level-1 DR Elections: 0 IS-IS: Level-2 DR Elections: 0
The next step is to compare the debugs and captures.
DeviceA
Jul 22 19:17:24.929: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 22 19:17:24.929: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 22 19:17:31.685: ISIS-Adj: Rec serial IIH from 6c31.0edb.3b5f (TenGigabitEthernet0/0/4) Jul 22 19:17:31.685: ISIS-Adj: cir type L1L2, cir id 0B, length 1496 Jul 22 19:17:31.685: ISIS-Adj: rcvd state UP, old state UP, new state UP, nbr usable TRUE Jul 22 19:17:31.685: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15 Jul 22 19:17:31.685: ISIS-Adj: Nghbr Ckt ID changed: FALSE Jul 22 19:17:31.685: ISIS-Adj: received Neighbor System-ID (must be our) 0000.0000.000A Jul 22 19:17:31.685: ISIS-Adj: received Neighbor ext.circuit ID (must be our) 0x5 Jul 22 19:17:31.685: ISIS-Adj: newstate:0, state_changed:0, going_up:0, going_down:0 Jul 22 19:17:31.685: ISIS-Adj: Action = ACCEPT Jul 22 19:17:31.685: ISIS-Adj: ACTION_ACCEPT: Jul 22 19:17:33.626: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 22 19:17:33.627: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 22 19:17:42.671: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 22 19:17:42.672: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 22 19:17:52.008: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 22 19:17:52.008: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 22 19:18:01.475: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15 Jul 22 19:18:01.475: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 22 19:18:01.685: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired Jul 22 19:18:01.685: ISIS-Adj: L1 adj count 0 Jul 22 19:18:01.685: ISIS-Adj: L2 adj count 0
DeviceB
Jul 22 19:17:25.693: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:17:25.693: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
Jul 22 19:17:27.882: ISIS-Adj: Rec serial IIH from a84f.b1c3.9484 (TwentyFiveGigE1/0/9)
Jul 22 19:17:27.882: ISIS-Adj: cir type L1L2, cir id 05, length 1496
Jul 22 19:17:27.882: ISIS-Adj: rcvd state UP, old state UP, new state UP, nbr usable TRUE
Jul 22 19:17:27.882: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15
Jul 22 19:17:27.882: ISIS-Adj: Nghbr Ckt ID changed: FALSE
Jul 22 19:17:27.882: ISIS-Adj: received Neighbor System-ID (must be our) 0000.0000.000B
Jul 22 19:17:27.882: ISIS-Adj: received Neighbor ext.circuit ID (must be our) 0xB
Jul 22 19:17:27.882: ISIS-Adj: newstate:0, state_changed:0, going_up:0, going_down:0
Jul 22 19:17:27.882: ISIS-Adj: Action = ACCEPT
Jul 22 19:17:27.882: ISIS-Adj: ACTION_ACCEPT:
Jul 22 19:17:34.637: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:17:34.637: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
Jul 22 19:17:36.579: ISIS-Adj: Rec serial IIH from a84f.b1c3.9484 (TwentyFiveGigE1/0/9)
Jul 22 19:17:36.579: ISIS-Adj: cir type L1L2, cir id 05, length 1496
Jul 22 19:17:36.579: ISIS-Adj: rcvd state UP, old state UP, new state UP, nbr usable TRUE
Jul 22 19:17:36.579: ISIS-Adj: RCV:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15
Jul 22 19:17:36.579: ISIS-Adj: Nghbr Ckt ID changed: FALSE
Jul 22 19:17:36.579: ISIS-Adj: received Neighbor System-ID (must be our) 0000.0000.000B
Jul 22 19:17:36.579: ISIS-Adj: received Neighbor ext.circuit ID (must be our) 0xB
Jul 22 19:17:36.579: ISIS-Adj: newstate:0, state_changed:0, going_up:0, going_down:0
Jul 22 19:17:36.579: ISIS-Adj: Action = ACCEPT
Jul 22 19:17:36.579: ISIS-Adj: ACTION_ACCEPT:
Jul 22 19:17:43.270: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:17:43.271: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
Jul 22 19:17:51.658: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:17:51.658: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
Jul 22 19:18:00.248: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:18:00.248: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
Jul 22 19:18:06.579: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired
Jul 22 19:18:06.579: ISIS-Adj: L1 adj count 0
Jul 22 19:18:06.579: ISIS-Adj: L2 adj count 0
Analysis of IS-IS debug logs:
- DeviceA sends a hello packet (Jul 22 19:17:24), DeviceB responds to this packet (Jul 22 19:17:25), DeviceA receives this response (Jul 22 19:17:31).
DeviceA
Jul 22 19:17:24.929: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15
Jul 22 19:17:24.929: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496
Jul 22 19:17:31.685: ISIS-Adj: Rec serial IIH from 6c31.0edb.3b5f (TenGigabitEthernet0/0/4)
DeviceB
Jul 22 19:17:25.693: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:17:25.693: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
Jul 22 19:17:27.882: ISIS-Adj: Rec serial IIH from a84f.b1c3.9484 (TwentyFiveGigE1/0/9)
- DeviceA sends another hello packet (Jul 22 19:17:33), DeviceB sends its hello packet (Jul 22 19:17:34), and two seconds later receives the packet from its peer.
DeviceA
Jul 22 19:17:33.626: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15
Jul 22 19:17:33.627: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496
DeviceB
Jul 22 19:17:34.637: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:17:34.637: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
Jul 22 19:17:36.579: ISIS-Adj: Rec serial IIH from a84f.b1c3.9484 (TwentyFiveGigE1/0/9)
- During the period that DeviceA does not receive the packet sent by DeviceB, the protocol declares itself down after 30 seconds.
DeviceA
Jul 22 19:17:42.671: ISIS-Adj: SND:3way Adj. Local Ckt ID:0x5 Nghbr Ckt ID:0xB Length:15
Jul 22 19:17:42.672: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496 Jul 22 19:18:01.475: ISIS-Adj: Sending serial IIH on TenGigabitEthernet0/0/4, 3way state:UP, length 1496
Jul 22 19:18:01.685: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceB (TenGigabitEthernet0/0/4) Down, hold time expired
- DeviceB does not receive any packet from its peer. After the default hold time period, this protocol declares itself down.
DeviceB
Jul 22 19:17:43.270: ISIS-Adj: SND:3way Adj. Local Ckt ID:0xB Nghbr Ckt ID:0x5 Length:15
Jul 22 19:17:43.271: ISIS-Adj: Sending serial IIH on TwentyFiveGigE1/0/9, 3way state:UP, length 1496
<snip>
Jul 22 19:18:06.579: %CLNS-5-ADJCHANGE: ISIS: Adjacency to DeviceA (TwentyFiveGigE1/0/9) Down, hold time expired
Captures analysis:
DeviceA receives packets from DeviceB, but the last packet that this router receives from the peer is at minute 13:17.31. Then DeviceA sends Hello packets
without any response from the peer.
ISIS Random Flaps DeviceA
DeviceB capture shows a similar condition, the switch receives the last hello packet from its peer, however, DeviceB starts to send its hello packets with no response.
ISIS Unstable DeviceB
In the exported captures, the hello packets are not delivered between peers. This problem appears to be with the transport.
Revision History
| Revision | Publish Date | Comments |
|---|---|---|
1.0 |
27-Jul-2023 |
Initial Release |
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