Misconfiguration is one of the root causes of problems in any network. Misconfiguration can be caused either by manual or system errors. You need to take extreme care while configuring an EIGRP routing protocol in a router, because even a small configuration error can affect the network traffic. Consider the scenario depicted in Figure 8.3. There are three routers, B1, B2, and B3, in an EIGRP network.
Figure 8.3: An EIGRP network with possibility for misconfigurations.
In Figure 8.3, simulate a few possible misconfigurations and define methods to solve them. The misconfigurations could be due to:
Network not declared in EIGRP
Same Autonomous System (AS) not defined in all routers in EIGRP domain
Network Not Declared in EIGRP
Consider a network segment 192.168.1.0/24 containing the secondary DNS server of the company with IP 192.168.1.10. The misconfiguration is caused by not declaring the network 192.168.1.0/24 in the EIGRP configurations. Table 8.4 shows the configurations of the three routers, B1, B2, and B3.
Router | Configuration |
---|---|
B1 | interface Ethernet 0 |
ip address 192.168.15.1 255.255.255.0 | |
! | |
interface Ethernet 1 | |
ip address 192.168.1.1 255.255.255.0 | |
! | |
router eigrp 10 | |
network 192.168.15.0 | |
! | |
B2 | interface Ethernet 0 |
ip address 192.168.15.2 255.255.255.0 | |
! | |
interface Ethernet 1 | |
ip address 192.168.2.1 255.255.255.0 | |
! | |
router eigrp 10 | |
network 192.168.2.0 | |
network 192.168.15.0 | |
! |
The end users connected to the LAN segments 192.168.2.0/24 and 192.168.3.0/24 are not able to browse the Internet because of the misconfiguration.
The steps to isolating the problem caused due to not declaring a network in the EIGRP domain are:
Note if the problem occurs when the primary DNS server, 192.168.2.4, is down.
Require users to contact the secondary DNS server, 192.168.1.1.
Issue a ping command to 192.168.1.1 from B2 and B3 to check connectivity to this server. A 100% failure is noted. The ping command is executed as shown in Listings 8.9 and 8.10.
Listing 8.9 Ping Command at B2
B2#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 0 percent (0/5)
Listing 8.10 Ping Command at B3
B3#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 0 percent (0/5)
Issue the commands:
B2#show ip route 192.168.1.0 % Network not in table B3#show ip route 192.168.1.0 % Network not in table
Check if B1 is an EIGRP neighbor of B3 and B2 using the show ip eigrp neighbors command. The output for the show ip eigrp neighbors command is shown in Listing 8.11 and Listing 8.12. This output confirms that B1, B2, and B3 are EIGRP neighbors.
Listing 8.11 Output of show ip eigrp neighbors Command at B2
B2#show ip eigrp neighbors IP-EIGRP neighbors for process 10 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 1 192.168.15.3 Se0 14 1w6d 48 288 0 3471 0 192.168.15.1 Et0 14 1w6d 3 200 0 8558
Listing 8.12 Output of show ip eigrp neighbors Command at B3
B3#show ip eigrp neighbors IP-EIGRP neighbors for process 10 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 1 192.168.15.2 Se0 14 1w6d 48 288 0 3471 0 192.168.15.1 Et0 14 1w6d 3 200 0 8558
Check the availability of route to network 192.168.1.0 at B1 using the show ip route 192.168.1.0 command. The output for the show ip route 192.168.1.0 command showing that 192.168.1.0 is a connected network is shown in Listing 8.13.
Listing 8.13 Output for show ip route 192.168.1.0 Command at B2
B2#show ip route 192.168.1.0 Routing entry for 192.168.1.0/24 Known via "connected", distance 0, metric 0 (connected, via interface) Routing Descriptor Blocks: * directly connected, via Ethernet1 Route metric is 0, traffic share count is 1
Check if EIGRP is enabled for this network in B1 using the show ip protocols command. The output for the show ip protocols command is shown in Listing 8.14.
Listing 8.14 Output for show ip protocols Command at B1
B1#show ip protocols Routing Protocol is "eigrp 10" Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Default networks flagged in outgoing updates Default networks accepted from incoming updates EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 EIGRP maximum hopcount 100 EIGRP maximum metric variance 1 Redistributing: static, eigrp 300 Automatic network summarization is in effect Maximum path: 4 Routing for Networks: 192.168.15.0 Passive Interface(s): Routing Information Sources: Gateway Distance Last Update 192.168.15.2 90 00:05:35 192.168.15.3 90 00:05:20 Distance: internal 90 external 170
Listing 8.14 shows the networks for which EIGRP routing takes place. EIGRP routing does not occur for network 192.168.1.0. The corrected configuration of B1 should be as shown in Listing 8.15.
Listing 8.15 Correct Configuration of B1
! interface Ethernet 0 ip address 192.168.15.1 255.255.255.0 ! interface Ethernet 1 ip address 192.168.1.1 255.255.255.0 ! router eigrp 10 network 192.168.15.0 network 192.168.1.0 !
Consider the same example depicted in Figure 8.3. Table 8.5 lists the configuration of the routers in the EIGRP network.
Router | Configuration |
---|---|
B1 | interface Ethernet 0 |
ip address 192.168.15.1 255.255.255.0 | |
! | |
interface Ethernet 1 | |
ip address 192.168.1.1 255.255.255.0 | |
! | |
router eigrp 10 | |
network 192.168.15.0 | |
! | |
B2 | interface Ethernet 0 |
ip address 192.168.15.2 255.255.255.0 | |
! | |
interface Ethernet 1 | |
ip address 192.168.2.1 255.255.255.0 | |
! | |
router eigrp 20 | |
network 192.168.2.0 | |
network 192.168.15.0 | |
! | |
B3 | interface Ethernet 0 |
ip address 192.168.15.3 255.255.255.0 | |
! | |
interface Ethernet 1 | |
ip address 192.168.3.1 255.255.255.0 | |
! | |
router eigrp 10 | |
network 192.168.3.0 | |
network 192.168.15.0 | |
! |
The users connected to the LAN segments 192.168.1.0/24 and 192.168.3.0/24 are not able to connect to the internal Web server, 192.168.2.5. This problem occurs because the same AS is not defined in all the routers in the EIGRP routing domain.
The steps to isolate the problem are:
Issue a ping command to network 192.168.2.5 from B1 and B3 to check connectivity using the ping 192.168.2.5 command. The output of the ping 192.168.2.5 command is shown in Listings 8.16 and 8.17.
Listing 8.16 Output of ping 192.168.2.5 Command at B1
B1#ping 192.168.2.5 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.2.5, timeout is 2 seconds: ..... Success rate is 0 percent (0/5)
Listing 8.17 Output of ping 192.168.2.5 Command at B3
B3#ping 192.168.2.5 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 192.168.2.5, timeout is 2 seconds: ..... Success rate is 0 percent (0/5)
The listings show a 100% failure of the ping command.
Issue the commands:
B1#show ip route 192.168.2.0 % Network not in table B3#show ip route 192.168.2.0 % Network not in table
The output of these commands shows there is no route available to the network.
Check if B2 is an EIGRP neighbor of B1 and B3 using the show ip eigrp neighbors command. Listings 8.18 and 8.19 show the output for the show ip eigrp neighbors command.
Listing 8.18 Output of show ip eigrp neighbors Command at B1
B1#show ip eigrp neighbors IP-EIGRP neighbors for process 10 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 1 192.168.15.3 Se0 14 1w6d 48 288 0 3471
Listing 8.19 Output of show ip eigrp neighbors Command at B3
B3#show ip eigrp neighbors IP-EIGRP neighbors for process 10 H Address Interface Hold Uptime SRTT RTO Q Seq (sec) (ms) Cnt Num 1 192.168.15.1 Et0 14 1w6d 3 200 0 8558
The listings show that B2 is not a neighbor of B1 and B3.
Check the availability of route to network 192.168.2.0 at B2 using the show ip route 192.168.1.0 command at B2. The output shows that 192.168.2.0 is a connected network
.Check if EIGRP is enabled for this network in B2 using the show ip protocols command. The output for the command is shown in Listing 8.20.
Listing 8.20 Output for show ip protocols Command at B2
B2#show ip protocols Routing Protocol is "eigrp 20" Outgoing update filter list for all interfaces is not set Incoming update filter list for all interfaces is not set Default networks flagged in outgoing updates Default networks accepted from incoming updates EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0 EIGRP maximum hopcount 100 EIGRP maximum metric variance 1 Redistributing: static, eigrp 300 Automatic network summarization is in effect Maximum path: 4 Routing for Networks: 192.168.2.0 192.168.15.0 Passive Interface(s): Routing Information Sources: Gateway Distance Last Update Distance: internal 90 external 170
Listing 8.20 shows that the Autonomous System Number (ASN) in B2 is 20 and is 10 in B1 and B3. The corrected configuration of B2 is shown in Listing 8.21.
Listing 8.21 Correct Configuration of B2
interface Ethernet 0 ip address 192.168.15.2 255.255.255.0 ! interface Ethernet 1 ip address 192.168.2.1 255.255.255.0 ! router eigrp 20 network 192.168.2.0 network 192.168.15.0 !