Auto-Summary Feature

Auto-summary feature is default enable in OS Version 12 & is disable in new Version 15.2 & other latest release
So we will discuss on Version 15 and on latest release.

So in new version of OS Auto-summary is disabled but we can enable this feature manually using command:

      *R3(config)#router eigrp 10
      *R3(config-router)#auto-summary
      *R3(config-router)#exit

Once we enable Auto-summary on a router that will start advertising all the prefixes on class default subnet mask & will suppress individual prefixes.

So this is the table before enabling Auto-summa

Commands to enable Auto-Summary

      *R3(config)#router eigrp 10
      *R3(config-router)#auto-summary
      *R3(config-router)#exit

After enabling Auto-Summary this output we get

We can see after enabling Router R3 is sending only single subnet and with class default subnet mask.

Neighbor Table

Now we will see the neighbor table view and will also discuss the entire component present in EIGRP neighbor table

We can run Sh ip eigrp neighbors command to get the output

*H
      here we see the count of the neighbor and that start from 0, so here we can see we have 2 neighbors one is 12.0.0.2 & other 14.0.0.4
*Address
      Here we see neighbor interface address by using this address router get’s hello packet from neighbor
*Interface
      This is the local interface on router that is used to connect neighbor
*Hold(sec)
      Here router is running a hold timer for the neighbor
      Router pick this hold time from the hello packet of the neighbor
      Timers can be different for different neighbor if neighbor has done some changes in hold timer
*Uptime
      This is the total up time of the neighbor
*SRTT(ms)
      Smooth Round Trip timer
      Is the average timer that router calculate by sending a packet and getting reply of the packet
*RTO
      Request Time out
      This is the time out timer for the neighbor
*Q Cnt
      Whenever a router sends a packet to EIGRP neighbor and did not get reply so QCnt will start increasing (depend on the number of packets)
      And if we see Q Cnt is 0, it means everything is fine and the neighborship is up.
*Seq Num
      This number indicate how many update packets we have received from the neighbor
      Updates including route with valid metric and with infinite metric also.

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