Neighborship Process

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Let’s enable EIGRP between two routers and will understand the concept of Neighborship between two EIGRP routers

      *R1(config)#router eigrp 10

      *R1(config-router)#network 12.0.0.0

      *R1(config-router)#exit

      *R2(config)#router eigrp 10

      *R2(config-router)#network 12.0.0.0

      *R2(config-router)#exit

Once we run the Network command under router EIGRP, it perform two task

      1. device check all the active interfaces belong to same subnet and put those subnets is local Topology Table

      2. device will start sending hello packets on the same interface to perform dynamic neighbor discovery

Now both routers will get hello from each other and now routers will send unicast Null update to each other with INIT flag enable & Seq number 1:- this null update does not carry any prefixes

      1. first R1 is sending first Null update packet to R2

      2. Then R2 is sending Null update to R1 and containing ACK of previous update received from R1

      3. Finally R1 is sending hello to R1 containing ACK of previous update packet received from R2

      4. EIGRP use Hello packet to give ACK to other router

      5. When you will do the practical, open all the packets to check the packet sequence how they are sending packet to each other and what they are containing*

After Null update if routers have other prefixes to share so they will send a full update (routers never send subnet information in update over the same link the subnet belongs to)

After every update routers send Ack to each other

               Check out our Complete EIGRP Video on Youtube