Other Useful IS-IS Troubleshooting Commands

Table 10-3 lists a few more IS-IS commands useful for troubleshooting. The commands are grouped by CLNS and IS-IS, IP and System. A few IS-IS and clns clear commands are also provided. Issuing the clear command usually clears data structures and resets related objects. The table also features useful debugging commands, some of which are discussed in the next section.

Consult the Cisco IOS Software command reference guides mentioned in the references at the end of this chapter for more information about the use and impact of each command before applying them on production routers ( specifically references 3 and 4).

Table 10-3. IS-IS Useful Troubleshooting Commands

CLNS show commands:	IS-IS show command:
show clns cache	show clns route
show clns traffic
show isis route
CLNS clear commands:	IS-IS clear command:
clear clns cache	clear isis *
clear clns es-neighbors
clear clns is-neighbors
clear clns neighbors
clear clns route
CLNS debug commands:	IS-IS debug commands:
debug clns events	debug isis adj-packets
debug clns packets	debug isis snp-packets
debug clns routing	debug isis spf-events
	debug isis spf-triggers
	debug isis spf-statistics
	debug isis update-packets
System show commands:	IP show commands:
show version	show ip protocol
show run	show ip route summary
	show ip traffic

Debugging IS-IS Problems

The CLNS and IS-IS debug commands shown in Table 10-3 are all useful for troubleshooting IS-IS problems. However, the following three debugging commands are the most useful and are commonly used. Each is discussed in more detail in the following subsections:

• debug isis adj-packets

• debug isis spf-events

• debug isis update-packets

debug isis adj-packets

As the name implies, the debug isis adj-packets command helps debug adjacency problems by displaying information about hello packets sent and received by a router. Adjacent routers send hellos to each other to maintain the adjacency for each level of routing, which can be viewed by using the debug isis adj-packets command (see Example 10-13). Note also that separate hello packets are exchanged for Level 1 and Level 2.

Example 10-13 debug isis adj-packets Command Output

 RT1#  debug isis adj-packets  IS-IS Adjacency related packets debugging is on RT1# Mar  6 20:25:13: ISIS-Adj: Sending L2 IIH on Ethernet0/0, length 1497 Mar  6 20:25:13: ISIS-Adj: Sending L1 IIH on Ethernet0/0, length 1497 Mar  6 20:25:15: ISIS-Adj: Rec L1 IIH from 00d0.58eb.ff01 (Ethernet0/0), cir ty7 Mar  6 20:25:16: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0/0), cir type L1L9 Mar  6 20:25:16: ISIS-Adj: rcvd state UP, old state UP, new state UP Mar  6 20:25:16: ISIS-Adj: Action = ACCEPT Mar  6 20:25:16: ISIS-Adj: Sending L2 IIH on Ethernet0/0, length 1497 Mar  6 20:25:16: ISIS-Adj: Sending L1 IIH on Ethernet0/0, length 1497 Mar  6 20:25:18: ISIS-Adj: Sending serial IIH on Serial0/0, length 1499 Mar  6 20:25:19: ISIS-Adj: Sending L1 IIH on Ethernet0/0, length 1497 Mar  6 20:25:19: ISIS-Adj: Sending L2 IIH on Ethernet0/0, length 1497 Mar  6 20:25:21: ISIS-Adj: Sending L1 IIH on Ethernet0/0, length 1497 Mar  6 20:25:22: ISIS-Adj: Sending L2 IIH on Ethernet0/0, length 1497 Mar  6 20:25:25: ISIS-Adj: Sending L2 IIH on Ethernet0/0, length 1497 Mar  6 20:25:25: ISIS-Adj: Rec L1 IIH from 00d0.58eb.ff01 (Ethernet0/0), cir ty7 Mar  6 20:25:25: ISIS-Adj: Sending L1 IIH on Ethernet0/0, length 1497 Mar  6 20:25:25: ISIS-Adj: Rec serial IIH from *HDLC* (Serial0/0), cir type L1L9 Mar  6 20:25:25: ISIS-Adj: rcvd state UP, old state UP, new state UP Mar  6 20:25:25: ISIS-Adj: Action = ACCEPT 

debug isis spf-events

The debug isis spf-events command enables debugging of events related to the SPF process. It provides a real-time output unlike the show isis spf-log command, which provides a history of SPF activities. Example 10-14 shows an output for the sequence of events that occur when Ethernet0/0 is shut down on RT1 (refer to Figure 10-2), causing it to flag its own LSP, and that learned from RT5, over this interface for SPF recalculation. The debug output also shows SPF-related events and recomputation of the Level 1 and Level 2 shortest path trees (SPTs).

Example 10-14 Debugging SPF Events

 RT1#  debug isis spf-events  RT1(config)#int e0/0 RT1(config-if)#shut RT1(config-if)#^Z Mar  6 20:17:26: ISIS-SPF: L1 LSP 1 (0000.0000.0001.00-00) flagged for recalculC Mar  6 20:17:26: ISIS-SPF: L1 LSP 5 (0000.0000.0005.00-00) flagged for recalculC Mar  6 20:17:28: ISIS-SPF: Compute L1 SPT Mar  6 20:17:28: ISIS-SPF: 3 nodes for level-1 Mar  6 20:17:28: ISIS-SPF: Move 0000.0000.0001.00-00 to PATHS, metric 0 Mar  6 20:17:28: ISIS-SPF: Add 0000.0000.0001.01-00 to TENT, metric 10 Mar  6 20:17:28: ISIS-SPF: Add 0000.0000.0001 to L1 route table, metric 0 Mar  6 20:17:28: ISIS-SPF: Move 0000.0000.0001.01-00 to PATHS, metric 10 Mar  6 20:17:28: ISIS-SPF: Aging L1 LSP 1 (0000.0000.0001.00-00), version 214 Mar  6 20:17:28: ISIS-SPF: Aging L2 LSP 2 (0000.0000.0001.00-00), version 208 Mar  6 20:17:28: ISIS-SPF: Aging L1 LSP 3 (0000.0000.0001.01-00), version 207 Mar  6 20:17:28: ISIS-SPF: Aging L2 LSP 4 (0000.0000.0002.00-00), version 209 Mar  6 20:17:28: ISIS-SPF: Aging L1 LSP 5 (0000.0000.0005.00-00), version 207 Mar  6 20:17:28: ISIS-SPF: Aging L2 LSP 6 (0000.0000.0006.01-00), version 112 Mar  6 20:17:28: ISIS-SPF: Aging L2 LSP 7 (0000.0000.0006.00-00), version 114 Mar  6 20:17:28: ISIS-SPF: Aging L2 LSP 8 (0000.0000.0001.01-00), version 1 Mar  6 20:17:33: ISIS-SPF: Compute L2 SPT Mar  6 20:17:33: ISIS-SPF: 5 nodes for level-2 Mar  6 20:17:33: ISIS-SPF: Move 0000.0000.0001.00-00 to PATHS, metric 0 Mar  6 20:17:33: ISIS-SPF: Add 49.0001 to L2 route table, metric 0 Mar  6 20:17:33: ISIS-SPF: Add 0000.0000.0001.01-00 to TENT, metric 10 Mar  6 20:17:33: ISIS-SPF: considering adj to 0000.0000.0002 (Serial0/0) metric Mar  6 20:17:33: ISIS-SPF:   (accepted) Mar  6 20:17:33: ISIS-SPF: Add 0000.0000.0002.00-00 to TENT, metric 10 Mar  6 20:17:33: ISIS-SPF:   Next hop 0000.0000.0002 (Serial0/0) Mar  6 20:17:33: ISIS-SPF: Move 0000.0000.0001.01-00 to PATHS, metric 10 Mar  6 20:17:33: ISIS-SPF: Move 0000.0000.0002.00-00 to PATHS, metric 10 Mar  6 20:17:33: ISIS-SPF: Add 49.0002 to L2 route table, metric 10 Mar  6 20:17:33: ISIS-SPF: Redundant IP route 10.1.2.0/255.255.255.0, metric 20d Mar  6 20:17:33: ISIS-SPF: Redundant IP route 11.1.1.2/255.255.255.255, metric d Mar  6 20:17:33: ISIS-SPF: Redundant IP route 11.1.1.6/255.255.255.255, metric d Mar  6 20:17:33: ISIS-SPF: Add 192.168.1.0/255.255.255.252 to IP route table, m0 Mar  6 20:17:33: ISIS-SPF: Next hop 0000.0000.0002/192.168.1.2 (Serial0/0) (rej) Mar  6 20:17:33: ISIS-SPF: Aging L1 LSP 1 (0000.0000.0001.00-00), version 214 Mar  6 20:17:33: ISIS-SPF: Aging L2 LSP 2 (0000.0000.0001.00-00), version 209 Mar  6 20:17:33: ISIS-SPF: Aging L1 LSP 3 (0000.0000.0001.01-00), version 207 Mar  6 20:17:33: ISIS-SPF: Aging L2 LSP 4 (0000.0000.0002.00-00), version 210 Mar  6 20:17:33: ISIS-SPF: Aging L1 LSP 5 (0000.0000.0005.00-00), version 207 Mar  6 20:17:33: ISIS-SPF: Aging L2 LSP 6 (0000.0000.0006.01-00), version 113 Mar  6 20:17:33: ISIS-SPF: Aging L2 LSP 7 (0000.0000.0006.00-00), version 115 Mar  6 20:17:33: ISIS-SPF: Aging L2 LSP 8 (0000.0000.0001.01-00), version 2 

debug isis update-packets

In IS-IS, update information is propagated by means of LSPs when changes occur in the network. CNSPs are sent only one time on point-to-point links after adjacency is formed , but periodically on broadcast links to compensate for unreliable advertisement of LSPs over such media. The debug update-packets command displays any update-related information, such as LSPs and CSNPs. The related command, debug isis snp-packets, displays only sequence number packets with more detail. Examples 10-15 and 10-16 show sample outputs of these debugs. Lines 1 and 2 of Example 10-15 are actually console logs for flapping Serial0/0. The debug output starts from line 3. In line 3, a new LSP is built; this line turns out to be different from the older copy. This, therefore, triggers a full SPF to be scheduled (line 5). Lines 6 and 7 show LSP exchange over Serial0/0. Lines 11 and 14 show the one-time CSNP exchange when a point-to-point link is first brought up. In lines 15, 16, 17, a PSNP is created to obtain complete LSPs for nodes 2 and 5 as a result of the CSNP exchange. In line 18, a Level 1 LSP is built apparently to set the attach bit. The change in the Level 1 LSP results in running SPF for Level 1 in line 23. In line 22, the new Level 1 LSP is sent out on Ethernet0/0 followed by a CSNP in line 23.

Example 10-15 debug isis update-packets Command Update

 RT1#  debug isis update-packets  (1) *Mar 2 23:25:02: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/0, chp (2) *Mar 2 23:25:03: %CLNS-5-ADJCHANGE: ISIS: Adjacency to RT2 (Serial0/0) Up, newy (3) *Mar  2 23:25:07: ISIS-Update: Building L2 LSP (4) *Mar  2 23:25:07: ISIS-Update: TLV contents different, code 16 (5) *Mar  2 23:25:07: ISIS-Update: Full SPF required (6) *Mar 2 23:25:07: ISIS-Update: Sending L2 LSP 0000.0000.0001.00-00, seq 160, ht0 (7) *Mar 2 23:25:07: ISIS-Update: Rec L2 LSP 0000.0000.0002.00-00, seq 1D16, ht 11, (8) *Mar  2 23:25:07: ISIS-Update: from SNPA *HDLC* (Serial0/0) (9) *Mar  2 23:25:07: ISIS-Update: LSP newer than database copy (10) *Mar  2 23:25:07: ISIS-Update: No change (11) *Mar  2 23:25:08: ISIS-SNP: Rec L2 CSNP from 0000.0000.0002 (Serial0/0) (12) *Mar  2 23:25:08: ISIS-SNP: Rec L2 PSNP from 0000.0000.0002 (Serial0/0) (13) *Mar  2 23:25:08: ISIS-SNP: PSNP entry 0000.0000.0001.00-00, seq 160, ht 1197 (14) *Mar  2 23:25:08: ISIS-Update: Sending L2 CSNP on Serial0/0 (15) *Mar 2 23:25:08: ISIS-Update: Build L2 PSNP entry for 0000.0000.0002.00-00, se6 (16) *Mar 2 23:25:08: ISIS-Update: Build L2 PSNP entry for 0000.0000.0006.00-00, se2 (17) *Mar  2 23:25:08: ISIS-Update: Sending L2 PSNP on Serial0/0 (18) *Mar  2 23:25:09: ISIS-Update: Building L1 LSP (19) *Mar  2 23:25:09: ISIS-Update: Important fields changed (20) *Mar  2 23:25:09: ISIS-Update: Important fields changed (21) *Mar  2 23:25:09: ISIS-Update: Full SPF required (22) *Mar 2 23:25:09: ISIS-Update: Sending L1 LSP 0000.0000.0001.00-00, seq 15A, ht0 (23) *Mar  2 23:25:09: ISIS-Update: Sending L1 CSNP on Ethernet0/0 

Example 10-16 debug isis snap-packets Command Output

 RT5#  debug isis snp-packets  IS-IS CSNP/PSNP packets debugging is on RT5# Mar  6 20:02:28: ISIS-SNP: Rec L1 CSNP from 0000.0000.0001 (Ethernet0/0) Mar  6 20:02:28: ISIS-SNP: CSNP range 0000.0000.0000.00-00 to FFFF.FFFF.FFFF.FFF Mar  6 20:02:28: ISIS-SNP: Same entry 0000.0000.0001.00-00, seq 15D Mar  6 20:02:28: ISIS-SNP: Same entry 0000.0000.0001.01-00, seq 104 Mar  6 20:02:28: ISIS-SNP: Same entry 0000.0000.0005.00-00, seq FEA 

CLNS ping and traceroute

In addition to the plethora of show and debug commands available for monitoring and troubleshooting IS-IS, the ping clns and traceroute clns commands come in handy for troubleshooting forwarding problems associated with the CLNP protocol. For these commands to work in an environment with dynamic IS-IS routing, you must use the clns router isis command to enable CLNP forwarding on the relevant interfaces. These commands provide the CLNP equivalents of the ping and traceroute for testing node reachability in the IS-IS domain. These commands are irrelevant in IP-only environments where the clns router isis command is not configured on the router interfaces.

However, this is certainly a troubleshooting capability that some network operators might find useful. The CLNS ping and traceroute commands are indispensable tools for dual IP/CLNP or pure ISO CLNS environments.

Examples 10-17 through 10-19 show the configuration and CLNS routing environment of RT5. Examples 10-20 and 10-21 show the CNLS environment from the perspective of RT2, which is located in area 49.0002. This capture of the general CLNS routing environment of Figure 10-3 provides background information to help you understand the CLNS ping and traceroute from RT5 through the backbone to RT6. Examples 10-22 and 10-23 show standard and extended CLNS ping from RT5 to RT6. Example 10-24 is the output of the debug clns packet command from Example 10-23. Examples 10-25 and 10-26 demonstrate how the standard and extended CLNS traceroute commands work.

Example 10-17 Configuration for RT5 in Figure 10-3

 RT5#  show running-config  clns routing ! interface Loopback0  ip address 11.1.1.5 255.255.255.255 ! interface Ethernet0/0  ip address 10.1.1.5 255.255.255.0  ip router isis  clns router isis ! router isis  passive-interface Loopback0  net 49.0001.0000.0000.0005.00  is-type level-1  metric-style wide 

Example 10-18 show clns route from RT5

 RT5#  show clns route  CLNS Prefix Routing Table 49.0001.0000.0000.0005.00, Local NET Entry 

Example 10-19 show isis route from RT5

 RT5#  show isis route  IS-IS Level-1 Routing Table - version 13975 System Id     Next-Hop  Interface   SNPA            Metric  State RT1           RT1       Et0/0       00d0.58f7.8941  10      Up    L2-IS RT5             -- Default route out of area - (via 1 L2-attached IS) System Id     Next-Hop  Interface   SNPA            Metric  State               RT1       Et0/0       00d0.58f7.8941  10      Up 

Example 10-20 show clns route from RT5

 RT2#  show clns route  CLNS Prefix Routing Table 49.0002.0000.0000.0002.00, Local NET Entry 49.0001 [110/10]   via RT1, IS-IS, Up, Serial0/0 49.0002 [110/0]   via RT2, IS-IS, Up 

Example 10-21 show isis route from RT2 from Figure 10-3

 RT2#  show isis route  IS-IS Level-1 Routing Table - version 6873 System Id       Next-Hop        Interface   SNPA            Metric  State RT6             RT6             Et0/0       00d0.58f7.8041  10      Up RT2             -- 

Example 10-22 CLNS Standard ping Command

 RT5#  ping clns 49.0002.0000.0000.0006.00  Type escape sequence to abort. Sending 5, 100-byte CLNS Echos with timeout 2 seconds !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 4/4/4 ms 

Example 10-23 CLNS Extended ping Command

 RT5#  ping  Protocol [ip]: clns Target CLNS address: 49.0002.0000.0000.0006.00 Repeat count [5]: 2 Datagram size [100]: Timeout in seconds [2]: Extended commands [n]: y Source CLNS address [49.0001.0000.0000.0005.00]: Include global QOS option? [yes]: Pad packet? [no]: Validate reply data? [no]: Data pattern [0xABCD]: Sweep range of sizes [n]: Verbose reply? [no]: Type escape sequence to abort. Sending 2, 100-byte CLNS Echos with timeout 2 seconds !! Success rate is 100 percent (2/2), round-trip min/avg/max = 4/4/4 ms 

Example 10-24 CLNS Packet Debugs During CLNS ping

 RT5#  debug clns packet  Mar 10 07:50:43: CLNS: Originating packet, size 100 Mar 10 07:50:43:       from 49.0001.0000.0000.0005.00       to 49.0002.0000.0000.0006.00       via 0000.0000.0001 (Ethernet0/0 00d0.58f7.8941) Mar 10 07:50:43: CLNS: Echo Reply PDU received on Ethernet0/0! Mar 10 07:50:43: CLNS: Originating packet, size 100 Mar 10 07:50:43:       from 49.0001.0000.0000.0005.00       to 49.0002.0000.0000.0006.00       via 0000.0000.0001 (Ethernet0/0 00d0.58f7.8941) Mar 10 07:50:43: CLNS: Echo Reply PDU received on Ethernet0/0! 

Example 10-25 CLNS Standard traceroute

 RT5#  traceroute clns 49.0002.0000.0000.0006.00  Type escape sequence to abort. Tracing the route to 49.0002.0000.0000.0006.00   1 49.0001.0000.0000.0001.00 0 msec ! 0 msec ! 0 msec !   2 49.0002.0000.0000.0002.00 0 msec ! 0 msec ! 0 msec !   3 49.0002.0000.0000.0006.00 0 msec ! 0 msec ! 0 msec ! 

Example 10-26 CLNS Extended traceroute Command

 RT5#  traceroute  Protocol [ip]: clns Target CLNS address: 49.0002.0000.0000.0006.00 Timeout in seconds [3]: Probe count [3]: Minimum Time to Live [1]: Maximum Time to Live [30]: Extended commands [n]: y Source CLNS address [49.0001.0000.0000.0005.00]: Include global QOS option? [yes]: Pad packet? [no]: Validate reply data? [no]: Data pattern [0x60CD]: Sweep range of sizes [n]: Verbose reply? [no]: Type escape sequence to abort. Tracing the route to 49.0002.0000.0000.0006.00   1 49.0001.0000.0000.0001.00 4 msec ! 0 msec ! 0 msec !   2 49.0002.0000.0000.0002.00 0 msec ! 0 msec ! 0 msec !   3 49.0002.0000.0000.0006.00 0 msec ! 0 msec ! 0 msec !