Lab Objective:
The focus of this lab is to hone your trouble isolation and resolution skills. This lab will include Layer 2 and Layer 3 technologies which fall within the scope of the current CCNP curriculum.
Lab Topology:
The lab network topology is illustrated below:
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IMPORTANT NOTE If you are using the www.howtonetwork.net racks, please download and paste the troubleshooting lab configurations. If you are using your own rack or lab, please modify this configuration to reflect the actual interface types, etc, that you have on your devices. Prior to beginning all labs, apply the pre-lab configuration for each individual device. When completing these labs, it is important to resolve the trouble tickets in the order in which they are listed because they build on each other. For example, if you begin with Trouble Ticket # 3, you might not get the expected resolution or result if you have not completed Trouble Ticket # 1 and Trouble Ticket # 2. It is very important to follow the order listed. |
Trouble Ticket # 1
You have received a call from the ISP indicating that the BGP adjacency between them and your edge router (R1) has gone down. Troubleshoot and resolve this issue.
Trouble Ticket # 2
You have received a call from the NOC indicating that users on all the 150.0.3.0/24 subnet are unable to reach the 198.1.1.0/24 subnet. At the moment, depart policy stipulates that IGP configurations cannot be modified until further notice. While adhering to the current restriction, troubleshoot and resolve this issue.
Trouble Ticket # 3
The NOC has called you to advise that after they enable BGP on R4, they failed to establish an adjacency with R3. Troubleshoot and resolve this issue.
Trouble Ticket # 4
You have received notification that users within AS 65500 are unable to reach the 150.4.4.0/24 subnet and vice-versa. Troubleshoot and resolve this issue.
Lab Solutions
Solution # 1
The issue is that the BGP peer IP address has been mis-configured on R2:
| R2#show running-config | include neighbor bgp log-neighbor-changes neighbor 10.0.0.10 remote-as 65500 neighbor 10.0.0.10 next-hop-self neighbor 201.0.0.1 remote-as 254 |
To resolve this issue, configure the correct BGP peer IP address on R2:
| R2(config)#router bgp 65500 R2(config-router)#no neighbor 201.0.0.1 remote-as 254 R2(config-router)#neighbor 210.0.0.1 remote-as 254 |
Solution # 2
The issue is that the BGP NEXT_HOP attribute is unchanged when routes are advertised from an iBGP speaker to another iBGP speaker. Therefore, because the 210.0.0.0/30 subnet is unknown to the routers in AS 65500, the 198.1.1.0/24 prefix will be marked as inaccessible. To resolve this issue, while adhering to the restrictions, implement the following on R2:
| R2(config)#router bgp 65500 R2(config-router)#neighbor 10.0.0.10 next-hop-self |
Solution # 3
The issue is that there is a BGP password mismatch between R3 and R4:
| R3#show running-config | section bgp router bgp 65500 no synchronization bgp router-id 3.3.3.3 bgp log-neighbor-changes network 150.0.3.0 mask 255.255.255.0 neighbor INTERNAL peer-group neighbor INTERNAL remote-as 65500 neighbor INTERNAL password CCNP2011 neighbor INTERNAL route-reflector-client neighbor 10.0.0.9 peer-group INTERNAL neighbor 10.0.0.14 peer-group INTERNAL no auto-summary |
| R4#show running-config | section bgp router bgp 65500 no synchronization bgp router-id 4.4.4.4 bgp log-neighbor-changes network 150.0.4.0 mask 255.255.255.255 neighbor 10.0.0.13 remote-as 65500 neighbor 10.0.0.13 password CCNP2O11 no auto-summary |
This password mis-configuration will cause the following error messages on these routers:
| R3# *Jul 10 05:22:23.507: %TCP-6-BADAUTH: Invalid MD5 digest from 10.0.0.14(32321) to 10.0.0.13(179) *Jul 10 05:22:25.507: %TCP-6-BADAUTH: Invalid MD5 digest from 10.0.0.14(32321) to 10.0.0.13(179) *Jul 10 05:22:29.507: %TCP-6-BADAUTH: Invalid MD5 digest from 10.0.0.14(32321) to 10.0.0.13(179) |
| R4# *Jul 10 04:01:39.919: %TCP-6-BADAUTH: Invalid MD5 digest from 10.0.0.13(14756) to 10.0.0.14(179) *Jul 10 04:01:43.919: %TCP-6-BADAUTH: Invalid MD5 digest from 10.0.0.13(14756) to 10.0.0.14(179) *Jul 10 04:01:51.919: %TCP-6-BADAUTH: Invalid MD5 digest from 10.0.0.13(14756) to 10.0.0.14(179) |
To resolve this issue, configure the correct password on R4:
| R4(config)#router bgp 65500 R4(config-router)#neighbor 10.0.0.13 password CCNP2011 |
Solution # 4
The issue is that the BGP network command configured on R4 is incorrect:
| R4#show running-config | section bgp router bgp 65500 no synchronization bgp router-id 4.4.4.4 bgp log-neighbor-changes network 150.0.4.0 mask 255.255.255.255 neighbor 10.0.0.13 remote-as 65500 no auto-summary |
To resolve this issue, configure the correct network statement under BGP:
| 4(config)#router bgp 65500 R4(config-router)#no network 150.0.4.0 mask 255.255.255.255 R4(config-router)#network 150.0.4.0 mask 255.255.255.255 |
Final Working Router Configurations
R1
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R1#term len 0 Current configuration : 971 bytes R1# |
R2
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R2#term len 0 Current configuration : 1104 bytes R2# |
R3
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R3#term len 0 Current configuration : 1526 bytes R3# |
R4
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R4#term len 0 Current configuration : 1024 bytes R4# |