Month: September 2018

Dynamic adjacencies are determined by sending multicast hello packets on 224.0.0.10 (IPv4) or FF02::A (IPv6). Static adjacencies are manually configured (typically deployed across networks not supporting broadcast or multicast). For both static and dynamic he following have to match in order for the adjacency to come up:

Authentication
K-Values
Autonomous system number
The Neighbours must be on a common subnet

Note that times (Hello and hold) do not need to match.

The default is hello timer is 60 seconds on NBMA networks and 5 seconds on other interfaces. To adjust the hello timer: ip hello-interval eigrp 100. By default the hold time is three times the hello, being either 15 seconds to 180 seconds. To adjust the hold time: ip hold-time eigrp 100

Note changing the hold timer, does not automatically change the hello timer, and vice-versa.

Information about each neighbour is recorded in the neighbour table. To see this, use the “show ip eigrp neighbors” command.

EIGRP-IPv4 VR(sia) Address-Family Neighbors for AS(100)
H   Address       Interface    Hold Uptime   SRTT   RTO  Q  Seq
                               (sec)         (ms)       Cnt Num
0   1.2.1.1       Fa0/1          13 00:00:05    1  3000  1  39
1   2.3.2.3       Fa0/0          11 04:12:28   72   432  0  8

Note the “Q Cnt” value from this command. This shows the number of enqueued reliable packets. i.e. packets that have not received an ACK. In a stable network this must be zero. A non zero amount over a prolonged period indicated a neighbour issue.

Note the “Seq Num” from this command. This shows the sequence number from the last reliable packet received from the neighbour.

“H” stands for “handle” and represents an internal number assigned to each number.