July 8, 2023

EIGRP Tables and Functions: The EIGRP Neighbor Table

2 min read

EIGRP like OSPF has three tables: NeighborTopology and Routing tables. However, donโ€™t be confused because not all EIGRP tables have the same build like OSPF.

The neighbour, topology, and routing tables are very important in implementing and troubleshooting EIGRP. I often neglect the topology and routing table before because what is important to me is that all neighbours are up. But this is not the case especially if you want to progress your learning to a higher Cisco certification level.

Letโ€™s start with the neighbour table.

If you want to know whether you have established adjacency with neighbouring EIGRP router and also to know the uptime, then you go to the neighbour table.

Neighbour table: show ip eigrp neighbor

H โ€“ Handle; it is the order in which the EIGRP adjacency is formed. It starts with 0 and so on so forth.

Address โ€“ This is your neighbour’s IP address, not the local IP address. Looking at the table it shows that the Nettle router has 2 adjacent neighbours: 192.168.103.3 and 192.168.102.2.

Interface โ€“ This is the interface of the neighbour connected.

Hold โ€“ this is the hold time value in seconds. This tells how long the router will hold a neighbour if it doesnโ€™t receive a hello. There are two default values: 15 seconds and 180 seconds.  The 15 seconds default value is from the 5-second-hello packet on high bandwidth links like PPP, Ethernet, HDLC, point-to-point ATM and frame-relay subinterfaces, and others greater than T1 circuits. The 180 seconds value is from the 60-second hello packet of slower T1 circuits.

Uptime โ€“ It tells how long the local router has established adjacency to its neighbour router.

SRTT โ€“ is the acronym for Smooth Round Trip Time. Its value is in milliseconds and tells how long an EIGRP is to be sent to the neighbour and for the local router to receive an acknowledgement of that packet. The table, it is showing us the value of 66. It is ok unless the value is 0 because the value of 0 indicates that there are no acknowledgement packets being received.

RTO โ€“ short for Retransmission Timeout whose value is also in milliseconds. It tells how long the packet will be retransmitted from the retransmission queue of the neighbour.

Q Cnt โ€“ short for Queue Count. It is the number of EIGRP packets whether it is an update packet, query packet or reply packet that the software is waiting to send. On the table, it is showing 0 which means it is good as there are no pending packets in the queue. There is some sort of unidirectional or congestion issue if the Q Cnt value is not decrementing because that means nothing is being received or acknowledged.

Seq Num โ€“ it is the sequence number. It is the last used sequence number in which the EIGRP received the last packet.

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