While primary emphasis has been placed on the use of show commands in the previous section, this section describes some of the debugging commands that can also be used to troubleshoot EIGRP. Keep in mind, however, debugging is very processor intensive and should only be used as a last resort, i.e. after all show commands and other troubleshooting methods and tools have been applied or attempted.
The debug ip routing [acl|static] command is a powerful troubleshooting tool and command. It should be noted, however, that while this command is not EIGRP specific, it provides useful and detailed information on routing table events. Following is a sample of the information that is printed by this command:
| R1#debug ip routing IP routing debugging is on R1# *Mar 3 23:03:35.673: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to down*Mar 3 23:03:35.673: RT: is_up: FastEthernet0/0 0 state: 4 sub state: 1 line: 0 has_route: True *Mar 3 23:03:35.677: RT: interface FastEthernet0/0 removed from routing table *Mar 3 23:03:35.677: RT: del 172.16.1.0/30 via 0.0.0.0, connected metric [0/0] *Mar 3 23:03:35.677: RT: delete subnet route to 172.16.1.0/30 *Mar 3 23:03:35.677: RT: NET-RED 172.16.1.0/30 *Mar 3 23:03:35.677: RT: Pruning routes for FastEthernet0/0 (3) *Mar 3 23:03:35.689: RT: delete route to 10.1.3.0 via 172.16.1.2, FastEthernet0/0 *Mar 3 23:03:35.689: RT: no routes to 10.1.3.0, flushing *Mar 3 23:03:35.689: RT: NET-RED 10.1.3.0/24 *Mar 3 23:03:35.689: RT: delete route to 10.1.2.0 via 172.16.1.2, FastEthernet0/0 *Mar 3 23:03:35.689: RT: no routes to 10.1.2.0, flushing *Mar 3 23:03:35.689: RT: NET-RED 10.1.2.0/24 *Mar 3 23:03:35.689: RT: delete route to 10.1.1.0 via 172.16.1.2, FastEthernet0/0 *Mar 3 23:03:35.689: RT: no routes to 10.1.1.0, flushing *Mar 3 23:03:35.693: RT: NET-RED 10.1.1.0/24*Mar 3 23:03:35.693: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 150: Neighbor 172.16.1.2 (FastEthernet0/0) is down: interface down *Mar 3 23:03:39.599: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 150: Neighbor 172.16.1.2 (FastEthernet0/0) is up: new adjacency *Mar 3 23:03:40.601: RT: is_up: FastEthernet0/0 1 state: 4 sub state: 1 line: 1 has_route: False *Mar 3 23:03:40.605: RT: add 172.16.1.0/30 via 0.0.0.0, connected metric [0/0]
*Mar 3 23:03:40.605: RT: NET-RED 172.16.1.0/30 |
You can use this command in conjunction with an ACL to view information about the route or routes referenced in the ACL. Additionally, the same command can also be used for troubleshooting static route events on the local device. As a side note, instead of using this command, if you are running EIGRP, consider using the show ip eigrp events command instead as it provides a history of EIGRP internal events, and can be used to troubleshoot SIA issues, as well as route flaps and other events. Following is a sample of the information that is printed by this command:
| R1#show ip eigrp events Event information for AS 150: 1 23:03:49.135 Ignored route, metric: 192.168.3.0 28160 2 23:03:49.135 Ignored route, metric: 192.168.2.0 28160 3 23:03:49.135 Ignored route, metric: 192.168.1.0 28160 4 23:03:49.131 Rcv EOT update src/seq: 172.16.1.2 85 5 23:03:49.127 Change queue emptied, entries: 3 6 23:03:49.127 Ignored route, metric: 192.168.3.0 28160 7 23:03:49.127 Ignored route, metric: 192.168.2.0 28160 8 23:03:49.127 Ignored route, metric: 192.168.1.0 28160 9 23:03:49.127 Metric set: 10.1.3.0/24 156160 10 23:03:49.127 Update reason, delay: new if 4294967295 11 23:03:49.127 Update sent, RD: 10.1.3.0/24 4294967295 12 23:03:49.127 Update reason, delay: metric chg 4294967295 13 23:03:49.127 Update sent, RD: 10.1.3.0/24 4294967295 14 23:03:49.123 Route install: 10.1.3.0/24 172.16.1.2 15 23:03:49.123 Find FS: 10.1.3.0/24 4294967295 16 23:03:49.123 Rcv update met/succmet: 156160 128256 17 23:03:49.123 Rcv update dest/nh: 10.1.3.0/24 172.16.1.2 18 23:03:49.123 Metric set: 10.1.3.0/24 4294967295 19 23:03:49.123 Metric set: 10.1.2.0/24 156160 20 23:03:49.123 Update reason, delay: new if 4294967295 21 23:03:49.123 Update sent, RD: 10.1.2.0/24 4294967295 22 23:03:49.123 Update reason, delay: metric chg 4294967295[Truncated Output] |
In addition to the debug ip routing command, two additional EIGRP-specific debugging commands are also available in Cisco IOS software. The debug eigrp command can be used to provide real-time information on the DUAL Finite State Machine, EIGRP neighbor relationships, Non-Stop Forwarding events, packets and transmission events. The options that are available with this command are shown below:
| R1#debug eigrp ? fsm EIGRP Dual Finite State Machine events/actions neighbors EIGRP neighbors nsf EIGRP Non-Stop Forwarding events/actions packets EIGRP packets transmit EIGRP transmission events |
In addition to the debug eigrp command, the debug ip eigrp command prints detailed information on EIGRP route events, such as how EIGRP processes incoming updates. The additional keywords that can be used in conjunction with this command are illustrated below:
| R1#debug ip eigrp ? <1-65535> Autonomous System neighbor IP-EIGRP neighbor debugging notifications IP-EIGRP event notifications summary IP-EIGRP summary route processing vrf Select a VPN Routing/Forwarding instance <cr> |
And in conclusion, following is sample output of the debug ip eigrp command:
| R1#debug ip eigrp IP-EIGRP Route Events debugging is on R1# *Mar 3 23:49:47.028: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 150: Neighbor 172.16.1.2 (FastEthernet0/0) is up: new adjacency *Mar 3 23:49:47.044: IP-EIGRP(Default-IP-Routing-Table:150): 10.1.0.0/24 – do advertise out FastEthernet0/0 *Mar 3 23:49:47.044: IP-EIGRP(Default-IP-Routing-Table:150): Int 10.1.0.0/24 metric 128256 – 256 128000 *Mar 3 23:49:48.030: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/0, changed state to up *Mar 3 23:49:56.179: IP-EIGRP(Default-IP-Routing-Table:150): Processing incoming UPDATE packet *Mar 3 23:49:56.544: IP-EIGRP(Default-IP-Routing-Table:150): Processing incoming UPDATE packet *Mar 3 23:49:56.544: IP-EIGRP(Default-IP-Routing-Table:150): Int 10.1.1.0/24 M 156160 – 25600 130560 SM 128256 – 256 128000 *Mar 3 23:49:56.544: IP-EIGRP(Default-IP-Routing-Table:150): route installed for 10.1.1.0 () *Mar 3 23:49:56.544: IP-EIGRP(Default-IP-Routing-Table:150): Int 10.1.2.0/24 M 156160 – 25600 130560 SM 128256 – 256 128000 *Mar 3 23:49:56.548: IP-EIGRP(Default-IP-Routing-Table:150): route installed for 10.1.2.0 () *Mar 3 23:49:56.548: IP-EIGRP(Default-IP-Routing-Table:150): Int 10.1.3.0/24 M 156160 – 25600 130560 SM 128256 – 256 128000[Truncated Output] |