EIGRP Verification
In the previous section we had quiet a few show commands to use with OSPF, well EIGRP will not be any different. There is a lot of information that can be very useful to the troubleshooting process that needs to be known with EIGRP. We know that EIGRP maintains 2 separate tables that hold information about routes and backup routes.
We've already went over the EIGRP routing table, so let's go ahead and take a look at the neighbor table in EIGRP.
This output lists each neighbor this router has through EIGRP. The H column indicates the order in which neighbors were formed. We can see that router 1 formed neighborship with router 2 before router 3. The next column tells us the neighbors IP address, and the next is the interface the neighbor was discovered on. The Hold Uptime column indicates how long the router will wait to receive a hello packet from the neighbor before it drops the neighbor. The SRTT column stands for Smooth Round Trip Timer, and it indicates the time it takes to get to the neighbor and back. The RTO is a restransmission indicator. The Q Cnt, or Queue count, tells if any messages are waiting to be processed. The sequence column keeps track of the updates received from neighbors.
There is quiet a bit of useful information that can be obtained from the neighbor table. Now let's take a look at the topology table.
There is quiet a bit of useful information that can be obtained from the neighbor table. Now let's take a look at the topology table.
As you can see, the topology table holds a lot of information. Here you can find information about successor and feasible successor routes, as well as advertised and feasible distances. Let's take a closer look at the route to router 5's LAN subnet 172.16.0.0/25.
The first thing to notice is the P next to the IP address. The P stands for passive and is a good thing. EIGRP routes will go to an Active state when they are searching for a route. The next thing to notice is that the route has 1 successor with a FD of 2835456, which we see below it is a route through 172.16.21.106 which is router 2. Notice that EIGRP is routing through router 2 instead of router 3. Remember in the last section we changed the bandwidth of the link to alter the OSPF route, then we change the cost of the other link to alter it back. Since EIGRP doesn't use cost to calculate a metric it is using the bandwidth setting to alter the route.
The entry directly underneath the successor route is a feasible successor. This route is a backup should the link to router 2 go down.
The entry directly underneath the successor route is a feasible successor. This route is a backup should the link to router 2 go down.
The output of 'show ip protocols' will displace information about the EIGRP configuration. We can see our EIGRP metric weight K values here. These values can be manipulated to adjust the EIGRP metric but that is beyond the CCNA curriculum. Instead we will just alter bandwidth and delay of the links to manipulate traffic. We see a line that says 'Automatic network summarization is in effect'. This line indicates that EIGRP is summarizing routes. Dis-contiguous networks will not work when EIGRP uses summarized routes. There is a simple fix for this -
Issuing the 'no auto' command in EIGRP configuration on every router in the network will allow dis-contiguous networks.
We also see a line in the output from 'show ip protocols' that says 'Maximum path: 4'. This states that EIGRP will load balance across 4 paths. So EIGRP will actually make use of each link by sending an appropriate amount of information across each one to achieve best throughput.
The ending of the 'show ip protocols' command displays which networks EIGRP has been configured to route for. It also displays the AD for EIGRP internal and external routes.
Now let's go ahead and manipulate the EIGRP network to adjust traffic and take a look at how EIGRP load balances.
We also see a line in the output from 'show ip protocols' that says 'Maximum path: 4'. This states that EIGRP will load balance across 4 paths. So EIGRP will actually make use of each link by sending an appropriate amount of information across each one to achieve best throughput.
The ending of the 'show ip protocols' command displays which networks EIGRP has been configured to route for. It also displays the AD for EIGRP internal and external routes.
Now let's go ahead and manipulate the EIGRP network to adjust traffic and take a look at how EIGRP load balances.