EIGRP Neighbor Establishing Packets

This is an EIGRP packet capture when initially forming adjacency. The setup we use is simple and has 2 routers with network 0.0.0.0 command which indicates advertise everything on every link.

Packet flow will be like the following.. (click on the images to view in full size)

1st let's analyze a Hello packet before the adjacency happen.

As you can see the K values are there and looks like by default it is supporting the wide metrics because K6 is there.

We can see there are 2 unicast Update packets exchanging. Let's see what is in it.

Actually nothing important like routing information is not there.. Looks like both routers are exchanging them for some other reason than exchanging routes.

Now let's see what is inside the 14th packet which is sent to the multicast address as an Update.

Now it is sending it's routes out. If we expand one route we can find all the valuable information about that route like metrics, next-hop, DUAL settings used to calculate the metric etc..
















Now we can see R2 is also sending a multicast Update. Let's see what is inside it..

Same routes which is advertised by R1? Well by split horizon rule it should not advertise the same routes to the neighbor it learned but looks like multicast does not care it. Anyway then the adjacency
is formed and Hello packets are exchanged to maintain the adjacency.

Looks like something actually does not work like in the book 😐

Download the packet capture from here.