Lab 6 - Configuring an EIGRP Network with Multiple ASNs

Submitted by Jason Neurohr on Wed, 08/19/2009 - 09:21

In this lab we'll configure an EIGRP network with multiple Autonomous System Numbers (ASNs), and redistribute the routing information between each ASN. We'll also play with EIGRPs Metrics, and configure Route Summarization. For this lab we'll be using content from some of the previous labs to cut out the leg work:

We'll use the same network design and IP addressing scheme from Lab 5 - Part 2 - Adding Additional Routers To The OSPF Network so check this out first if you haven't already.

Make sure to check out the other EIGRP labs for more info and configuration examples.

The Network:

Lab 6 - Multiple EIGRP ASN

Configuring EIGRP

The first thing we'll do is configure our EIGRP ASNs. The network consists of three ASNs, and using the redistribute EIGRP router subcommand to redistribute the routes between each ASN. Similarly to OSPF will use wildcard masks with our network statements (although this isn't required).

R0(config)#router eigrp 10
R0(config-router)#no auto-summary
R0(config-router)#network 10.0.0.0 0.0.0.3
R0(config-router)#network 192.168.1.0 0.0.0.255

R1(config)#router eigrp 10
R1(config-router)#no auto-summary
R1(config-router)#network 10.0.0.0 0.0.0.3
R1(config)#router eigrp 20
R1(config-router)#no auto-summary
R1(config-router)#network 10.1.1.0 0.0.0.3
R1(config-router)#redistribute eigrp 10
R1(config)#router eigrp 10
R1(config-router)#redistribute eigrp 20

R2(config)#router eigrp 20
R2(config-router)#no auto-summary
R2(config-router)#network 10.1.1.0 0.0.0.3
R2(config)#router eigrp 30
R2(config-router)#no auto-summary
R2(config-router)#redistribute eigrp 20
R2(config-router)#network 10.2.3.0 0.0.0.3   
R2(config-router)#network 10.2.4.0 0.0.0.3
R2(config-router)#router eigrp 20
R2(config-router)#redistribute eigrp 30

R3(config)#router eigrp 30
R3(config-router)#no auto-summary
R3(config-router)#network 10.2.3.0 0.0.0.3
R3(config-router)#network 10.3.5.0 0.0.0.3
R3(config-router)#network 10.3.6.0 0.0.0.3
R3(config-router)#network 172.16.3.0 0.0.0.255

R4(config)#router eigrp 30
R4(config-router)#no auto-summary
R4(config-router)#network 10.2.4.0 0.0.0.3
R4(config-router)#network 10.4.5.0 0.0.0.3
R4(config-router)#network 172.16.4.0 0.0.0.255

R5(config)#router eigrp 30
R5(config-router)#no auto-summary
R5(config-router)#network 10.3.5.0 0.0.0.3
R5(config-router)#network 10.4.5.0 0.0.0.3
R5(config-router)#network 172.16.5.0 0.0.0.255

R6(config)#router eigrp 30
R6(config-router)#no auto-summary
R6(config-router)#network 10.3.6.0 0.0.0.3
R6(config-router)#network 172.16.6.0 0.0.0.255

Once the EIGRP configuration is complete the routing table on R0 looks like the below:

Gateway of last resort is not set

     172.16.0.0/24 is subnetted, 4 subnets
D EX    172.16.4.0 [170/161280] via 10.0.0.2, 00:47:04, FastEthernet0/0
D EX    172.16.5.0 [170/163840] via 10.0.0.2, 00:44:35, FastEthernet0/0
D EX    172.16.6.0 [170/163840] via 10.0.0.2, 00:41:38, FastEthernet0/0
D EX    172.16.3.0 [170/161280] via 10.0.0.2, 00:42:56, FastEthernet0/0
     10.0.0.0/30 is subnetted, 7 subnets
D EX    10.1.1.0 [170/30720] via 10.0.0.2, 00:56:27, FastEthernet0/0
C       10.0.0.0 is directly connected, FastEthernet0/0
D EX    10.4.5.0 [170/35840] via 10.0.0.2, 00:47:04, FastEthernet0/0
D EX    10.2.3.0 [170/33280] via 10.0.0.2, 00:50:15, FastEthernet0/0
D EX    10.3.5.0 [170/35840] via 10.0.0.2, 00:43:11, FastEthernet0/0
D EX    10.2.4.0 [170/33280] via 10.0.0.2, 00:47:06, FastEthernet0/0
D EX    10.3.6.0 [170/35840] via 10.0.0.2, 00:43:05, FastEthernet0/0
C    192.168.1.0/24 is directly connected, Loopback0

Running traceroute from R0 to the loopback interface on R5:

R0#traceroute 172.16.5.1

Type escape sequence to abort.
Tracing the route to 172.16.5.1

  1 10.0.0.2 12 msec 16 msec 16 msec
  2 10.1.1.2 24 msec 20 msec 40 msec
  3 10.2.4.2 52 msec 16 msec 52 msec
  4 10.4.5.2 28 msec *  20 msec

Running a ping from R0 to the loopback interface on R5:

R0#ping 172.16.6.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.6.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/44/72 ms

The routing table on R5 looks like the below:

Gateway of last resort is not set

     172.16.0.0/24 is subnetted, 4 subnets
D       172.16.4.0 [90/156160] via 10.4.5.1, 00:44:12, FastEthernet1/0
C       172.16.5.0 is directly connected, Loopback0
D       172.16.6.0 [90/158720] via 10.3.5.1, 00:42:42, FastEthernet0/0
D       172.16.3.0 [90/156160] via 10.3.5.1, 00:43:59, FastEthernet0/0
     10.0.0.0/30 is subnetted, 7 subnets
D EX    10.1.1.0 [170/33280] via 10.4.5.1, 00:44:13, FastEthernet1/0
                 [170/33280] via 10.3.5.1, 00:44:13, FastEthernet0/0
D EX    10.0.0.0 [170/35840] via 10.4.5.1, 00:44:13, FastEthernet1/0
                 [170/35840] via 10.3.5.1, 00:44:13, FastEthernet0/0
C       10.4.5.0 is directly connected, FastEthernet1/0
D       10.2.3.0 [90/30720] via 10.3.5.1, 00:44:13, FastEthernet0/0
C       10.3.5.0 is directly connected, FastEthernet0/0
D       10.2.4.0 [90/30720] via 10.4.5.1, 00:44:13, FastEthernet1/0
D       10.3.6.0 [90/30720] via 10.3.5.1, 00:44:09, FastEthernet0/0
D EX 192.168.1.0/24 [170/163840] via 10.4.5.1, 00:44:13, FastEthernet1/0
                    [170/163840] via 10.3.5.1, 00:44:13, FastEthernet0/0

Running traceroute from R5 to the loopback interface on R0:

R5#traceroute 192.168.1.1

Type escape sequence to abort.
Tracing the route to 192.168.1.1

  1 10.4.5.1 12 msec
    10.3.5.1 8 msec
    10.4.5.1 8 msec
  2 10.2.3.1 12 msec
    10.2.4.1 12 msec
    10.2.3.1 12 msec
  3 10.1.1.1 20 msec 20 msec 20 msec
  4 10.0.0.1 32 msec *  40 msec

Running a ping from R5 to the loopback interface on R0:

R5#ping 192.168.1.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/36/56 ms

Influencing the Route Table

R5 currently has two Successor routes to the 192.168.1.0/24 subnet via R3 and R4, as both these routes have the same Feasible Distance (metric). Lets say we wanted the traffic to only go via R3. To make this happen we'll set R5s interface connecting to R4 with a lower bandwidth value, which will make the FD higher then the R5-R3 route. This is an exert from R5s routing table showing the two Successor routes:

D EX 192.168.1.0/24 [170/163840] via 10.4.5.1, 00:00:18, FastEthernet1/0
                    [170/163840] via 10.3.5.1, 00:00:18, FastEthernet0/0

You can also view them in the eigrp topology table, using the show ip eigrp topology all-links:

P 192.168.1.0/24, 2 successors, FD is 163840, serno 33
        via 10.3.5.1 (163840/161280), FastEthernet0/0
        via 10.4.5.1 (163840/161280), FastEthernet1/0

Using the bandwidth interface subcommand we'll lower the bandwidth value for the fastethernet 1/0 interface, and the clear the routing table:

R5#configure terminal
R5(config)#interface fastethernet 1/0
R5(config-if)#bandwidth 10000
R5(config-if)#^Z
R5#clear ip route *

The routing table will then update and you can now see that there is only one route present via R3:

Gateway of last resort is not set

     172.16.0.0/24 is subnetted, 4 subnets
D       172.16.4.0 [90/161280] via 10.3.5.1, 00:00:07, FastEthernet0/0
C       172.16.5.0 is directly connected, Loopback0
D       172.16.6.0 [90/158720] via 10.3.5.1, 00:00:11, FastEthernet0/0
D       172.16.3.0 [90/156160] via 10.3.5.1, 00:00:11, FastEthernet0/0
     10.0.0.0/30 is subnetted, 7 subnets
D EX    10.1.1.0 [170/33280] via 10.3.5.1, 00:00:07, FastEthernet0/0
D EX    10.0.0.0 [170/35840] via 10.3.5.1, 00:00:07, FastEthernet0/0
C       10.4.5.0 is directly connected, FastEthernet1/0
D       10.2.3.0 [90/30720] via 10.3.5.1, 00:00:07, FastEthernet0/0
C       10.3.5.0 is directly connected, FastEthernet0/0
D       10.2.4.0 [90/33280] via 10.3.5.1, 00:00:07, FastEthernet0/0
D       10.3.6.0 [90/30720] via 10.3.5.1, 00:00:11, FastEthernet0/0
D EX 192.168.1.0/24 [170/163840] via 10.3.5.1, 00:00:07, FastEthernet0/0

Again viewing the EIGRP topology table you can still see both routes however you'll notice the FD (metric) of the route via R4 is now higher:

P 192.168.1.0/24, 1 successors, FD is 163840, serno 41
        via 10.3.5.1 (163840/161280), FastEthernet0/0
        via 10.4.5.1 (394240/161280), FastEthernet1/0

Using traceroute we can verify that our traffic is now going via R3 only:

R5#traceroute 192.168.1.1

Type escape sequence to abort.
Tracing the route to 192.168.1.1

  1 10.3.5.1 16 msec 44 msec 8 msec
  2 10.2.3.1 16 msec 12 msec 48 msec
  3 10.1.1.1 28 msec 28 msec 32 msec
  4 10.0.0.1 40 msec *  64 msec

EIGRP Route Summarization

We'll now configure route summarization to summarize the 172.16.*.0/24 subnets. Right now the routing table on R0 contains an individual route for each of the 172.16.*.0/24 subnets. To make the routing table updates/and the table itself smaller, we'll enable route summarization on R2 to summarize these subnets into a single route:

R0s route table:

Gateway of last resort is not set

     172.16.0.0/24 is subnetted, 4 subnets
D EX    172.16.4.0 [170/161280] via 10.0.0.2, 00:58:41, FastEthernet0/0
D EX    172.16.5.0 [170/163840] via 10.0.0.2, 00:56:12, FastEthernet0/0
D EX    172.16.6.0 [170/163840] via 10.0.0.2, 00:53:15, FastEthernet0/0
D EX    172.16.3.0 [170/161280] via 10.0.0.2, 00:54:33, FastEthernet0/0
     10.0.0.0/30 is subnetted, 7 subnets
D EX    10.1.1.0 [170/30720] via 10.0.0.2, 01:08:04, FastEthernet0/0
C       10.0.0.0 is directly connected, FastEthernet0/0
D EX    10.4.5.0 [170/35840] via 10.0.0.2, 00:03:27, FastEthernet0/0
D EX    10.2.3.0 [170/33280] via 10.0.0.2, 01:01:52, FastEthernet0/0
D EX    10.3.5.0 [170/35840] via 10.0.0.2, 00:54:48, FastEthernet0/0
D EX    10.2.4.0 [170/33280] via 10.0.0.2, 00:58:43, FastEthernet0/0
D EX    10.3.6.0 [170/35840] via 10.0.0.2, 00:54:42, FastEthernet0/0
C    192.168.1.0/24 is directly connected, Loopback0

EIGRP route summarization is configured at the interface configuration level unlike OSPF which is done at the router configuration level. In this case we configure the summarization using the ip summary-address command on the fastethernet interface which is the interface between R2 and R1. Let's take a quick look at how we work out what the summary address would be. First right out the subnets where trying to summarize:

172.16.3.0/24
172.16.4.0/24
172.16.5.0/24
172.16.6.0/24

In order write the binary equivalent of each address. Once you have them all match each binary bit from left to right, once you reach a row of bits that are not all matching make a mark. In this case I've put brackets around the matching bits:

[10101100.00010000.00000]011.00000000
[10101100.00010000.00000]100.00000000
[10101100.00010000.00000]101.00000000
[10101100.00010000.00000]110.00000000

As you can see the first 21 bits are the same. To get the summary address number write the first 21 bits as they are above, then make the remaining bits 0. Then just convert that back to decimal.

[10101100.00010000.00000000.00000000] = 172.16.0.0

Next we'll work out the summary address mask, to do this write the first 21 matching bits as 1's, then set the remaining bits to 0. Finally convert the address back to decimal:

[10101100.00010000.00000000.00000000] = 255.255.248.0

And that's how you work out the summary address. Now that we have the summary address and mask lets configure summarization on R2:

R2(config)#interface fastethernet 0/0
R2(config-if)#ip summary-address eigrp 20 172.16.0.0 255.255.248.0

Now that we've configured the route summarization, the route table on R0 now shows a single route for all our 172.16.*.0/24 subnets as 172.16.0.0/21.:

Gateway of last resort is not set

     172.16.0.0/21 is subnetted, 1 subnets
D EX    172.16.0.0 [170/161280] via 10.0.0.2, 00:00:05, FastEthernet0/0
     10.0.0.0/30 is subnetted, 7 subnets
D EX    10.1.1.0 [170/30720] via 10.0.0.2, 00:10:47, FastEthernet0/0
C       10.0.0.0 is directly connected, FastEthernet0/0
D EX    10.4.5.0 [170/35840] via 10.0.0.2, 00:03:32, FastEthernet0/0
D EX    10.2.3.0 [170/33280] via 10.0.0.2, 00:03:32, FastEthernet0/0
D EX    10.3.5.0 [170/35840] via 10.0.0.2, 00:03:32, FastEthernet0/0
D EX    10.2.4.0 [170/33280] via 10.0.0.2, 00:03:32, FastEthernet0/0
D EX    10.3.6.0 [170/35840] via 10.0.0.2, 00:03:32, FastEthernet0/0
C    192.168.1.0/24 is directly connected, Loopback0

We'll verify we still have connectivity by pinging the loopback interface on R6:

R0#ping 172.16.6.1

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.6.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/44/88 ms

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