RT1#debug eigrp packets EIGRP Packets debugging is on (UPDATE, REQUEST, QUERY, REPLY, HELLO, IPXSAP, PROBE, ACK, STUB, SIAQUERY, SIAREPLY) RT1# 00:01:00: EIGRP: Sending HELLO on FastEthernet0/0 00:01:00: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 00:01:05: EIGRP: Sending HELLO on FastEthernet0/0 00:01:05: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 00:01:07: EIGRP: Received HELLO on FastEthernet0/0 nbr 10.10.10.2 00:01:07: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 00:01:07: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.10.10.2 (FastEthernet0/0) is up: new adjacency 00:01:07: EIGRP: Enqueueing UPDATE on FastEthernet0/0 nbr 10.10.10.2 iidbQ un/rely 0/1 peerQ un/rely 0/0 serno 1-1 00:01:07: EIGRP: Requeued unicast on FastEthernet0/0 00:01:07: EIGRP: Sending UPDATE on FastEthernet0/0 nbr 10.10.10.2 00:01:07: AS 100, Flags 0x9, Seq 1/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 1-1 00:01:09: EIGRP: Sending UPDATE on FastEthernet0/0 nbr 10.10.10.2, retry 1, RTO 3000 00:01:09: AS 100, Flags 0x9, Seq 1/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 1-1 00:01:09: EIGRP: Sending HELLO on FastEthernet0/0 00:01:09: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 00:01:10: EIGRP: Received UPDATE on FastEthernet0/0 nbr 10.10.10.2 00:01:10: AS 100, Flags 0x9, Seq 1/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 00:01:10: EIGRP: Enqueueing UPDATE on FastEthernet0/0 iidbQ un/rely 0/1 serno 2-2 00:01:10: EIGRP: Building Sequence TLV 00:01:10: EIGRP: Enqueueing UPDATE on FastEthernet0/0 nbr 10.10.10.2 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 2-2 00:01:10: EIGRP: Sending HELLO with Sequence TLV on FastEthernet0/0, seq 2 00:01:10: EIGRP: Sending HELLO on FastEthernet0/0 00:01:10: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 00:01:10: EIGRP: Sending UPDATE on FastEthernet0/0 00:01:10: AS 100, Flags 0x2, Seq 2/0 idbQ 0/0 iidbQ un/rely 0/0 serno 2-2 00:01:11: EIGRP: Received HELLO on FastEthernet0/0 nbr 10.10.10.2 00:01:11: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 00:01:12: EIGRP: Received UPDATE on FastEthernet0/0 nbr 10.10.10.2 00:01:12: AS 100, Flags 0x9, Seq 1/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2, last received seq 1, out of sequence, this seq 1 00:01:12: EIGRP: Sending UPDATE on FastEthernet0/0 nbr 10.10.10.2, retry 2, RTO 4500 00:01:12: AS 100, Flags 0x9, Seq 1/1 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 serno 1-1 00:01:12: EIGRP: Received ACK on FastEthernet0/0 nbr 10.10.10.2 00:01:12: AS 100, Flags 0x0, Seq 0/1 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/2 00:01:12: EIGRP: Sending UPDATE on FastEthernet0/0 nbr 10.10.10.2 00:01:12: AS 100, Flags 0x0, Seq 2/1 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 serno 2-2 00:01:13: EIGRP: Received ACK on FastEthernet0/0 nbr 10.10.10.2 00:01:13: AS 100, Flags 0x0, Seq 0/2 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/1 00:01:13: EIGRP: FastEthernet0/0 multicast flow blocking cleared 00:01:14: EIGRP: Sending HELLO on FastEthernet0/0 00:01:14: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 00:01:16: EIGRP: Received HELLO on FastEthernet0/0 nbr 10.10.10.2 00:01:16: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0 00:01:18: EIGRP: Sending HELLO on FastEthernet0/0 00:01:18: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 00:01:21: EIGRP: Received HELLO on FastEthernet0/0 nbr 10.10.10.2 00:01:21: AS 100, Flags 0x0, Seq 0/0 idbQ 0/0 iidbQ un/rely 0/0 peerQ un/rely 0/0 RT1# RT1#sh ip route Gateway of last resort is not set 172.16.0.0/24 is subnetted, 1 subnets D 172.16.1.0 [90/30720] via 10.10.10.2, 00:00:28, FastEthernet0/0 10.0.0.0/24 is subnetted, 1 subnets C 10.10.10.0 is directly connected, FastEthernet0/0 RT1# RT1#sh ip eigrp topology all-links IP-EIGRP Topology Table for AS(100)/ID(10.10.10.1) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 10.10.10.0/24, 1 successors, FD is 28160, serno 1 via Connected, FastEthernet0/0 P 172.16.1.0/24, 1 successors, FD is 30720, serno 2 via 10.10.10.2 (30720/28160), FastEthernet0/0 RT1# RT1#sh ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 10.10.10.2 Fa0/0 597 00:00:20 396 2376 0 1 RT1# ====================================================================== RT2#sh ip eigrp neighbors IP-EIGRP neighbors for process 100 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 0 10.10.10.1 Fa0/0 597 00:00:25 1680 5000 0 2 RT2# RT2#sh ip eigrp topology all-links IP-EIGRP Topology Table for AS(100)/ID(10.10.10.2) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 10.10.10.0/24, 1 successors, FD is 28160, serno 1 via Connected, FastEthernet0/0 P 172.16.1.0/24, 1 successors, FD is 28160, serno 2 via Connected, FastEthernet1/0 RT2#
The debug eigrp packets privileged command traces the transmission and reception of EIGRP packets. Hello packets are sent unreliably, hence the sequence number (Seq) does not increment.
When the router sends the final update packet after the EIGRP convergence to its neighboring router, values appear in the sequence number field – Seq 2/1 indicates that the router sends an update packet with a sequence number of 2 and acknowledges the receipt of a packet with a sequence number of 1 from its neighboring router. The Seq Num field in the outputs of the show ip eigrp neighbors EXEC command on both routers reflect this information.
Eventually, RT1 and RT2 are expecting to receive the next reliable packet from the corresponding neighbor with a sequence number of 2 and 3 respectively.
The serial number (serno 2-2) indicates the number of changes that the 2 neighboring routers register in their EIGRP topology tables.
The sequence number increments each time an update, query, or reply packet is sent; while the serial number increments each time the topology table changes. Therefore, if the topology table has more than 100 changes, the serial number increases substantially, but the sequence number may only increase by 1.
The debug eigrp packets privileged command must be used with caution and only use it when diving deeper into a problem. Never start troubleshooting EIGRP with this command.
Below shows the output of the debug ip eigrp privileged command captured on a router:
RT1#debug ip eigrp IP-EIGRP Route Events debugging is on RT1# 00:00:44: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor 10.10.10.2 (FastEthernet0/0) is up: new adjacency 00:00:44: IP-EIGRP(Default-IP-Routing-Table:100): 10.10.10.0/24 - do advertise out FastEthernet0/0 00:00:46: IP-EIGRP(Default-IP-Routing-Table:100): Processing incoming UPDATE packet 00:00:46: IP-EIGRP(Default-IP-Routing-Table:100): Int 172.16.1.0/24 M 30720 - 25600 5120 SM 28160 - 25600 2560 00:00:46: IP-EIGRP(Default-IP-Routing-Table:100): Int 172.16.1.0/24 metric 30720 - 25600 5120 00:00:46: IP-EIGRP(Default-IP-Routing-Table:100): 10.10.10.0/24 - do advertise out FastEthernet0/0 00:00:47: IP-EIGRP(Default-IP-Routing-Table:100): Int 172.16.1.0/24 metric 30720 - 25600 5120 RT1# RT1#sh ip eigrp topology IP-EIGRP Topology Table for AS(100)/ID(10.10.10.1) Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply, r - reply Status, s - sia Status P 10.10.10.0/24, 1 successors, FD is 28160 via Connected, FastEthernet0/0 P 172.16.1.0/24, 1 successors, FD is 30720 via 10.10.10.2 (30720/28160), FastEthernet0/0 RT1#
The debug ip eigrp [neighbor as-num neighbor-id] privileged command verifies the operation of EIGRP.
The EIGRP metric is equal to the bandwidth plus the delay by default. The EIGRP process uses the source metric (SM) information in the update packet to calculate the advertised distance (AD) from a neighboring router and place it into the EIGRP topology table. In this example, the SM for 172.16.1.0/24 via 10.10.10.2 is SM 28160 – 25600 2560, which means the source metric (AD) is 25600 (bandwidth) + 2560 (delay) = 28160.
The EIGRP metric calculation for the total delay uses the metric (M) information in the update. In this example, the M information is M 30720 – 25600 5120, which means the metric (FD) is 25600 (bandwidth) + 5120 (delay) = 30720.
RT1#sh ip eigrp topology 172.16.1.0/24 IP-EIGRP (AS 100): Topology entry for 172.16.1.0/24 State is Passive, Query origin flag is 1, 1 Successor(s), FD is 30720 Routing Descriptor Blocks: 10.10.10.2 (FastEthernet0/0), from 10.10.10.2, Send flag is 0x0 Composite metric is (30720/28160), Route is Internal Vector metric: Minimum bandwidth is 100000 Kbit Total delay is 200 microseconds Reliability is 255/255 Load is 1/255 Minimum MTU is 1500 Hop count is 1 RT1#
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