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 Level 1 support indicating that following some scheduled changes, they have lost connectivity to router R2. Troubleshoot and resolve this issue.
Trouble Ticket # 2
Users are complaining about excessive latency between the 150.1.1.0/24 and 150.3.3.0/24 subnet. Previously, this traffic was load-shared across R2 because of the low-bandwidth 512Kbps connecting R1 and R3. Troubleshoot and resolve this issue.
Trouble Ticket # 3
You have received several complaints that the NOC is unable to reach some Loopback subnets configured on R1 from the other routers. Management has forbidden the modification of the EIGRP configuration on R1. With this restriction in mind, troubleshoot and resolve this issue.
Trouble Ticket # 4
You have received an urgent call from the NOC stating that while they were troubleshooting TCP connectivity issues between the 150.4.4.0/24 and 150.1.1.0/24 subnets they lost all connectivity to R4. Troubleshoot and resolve this issue.
Lab Solutions
Solution # 1
The issue is that R2 has been configured with all interfaces, except for FastEthernet0/0, as passive under EIGRP. This prevents the router from forming neighbor relationships with routers running EIGRP in the same autonomous system:
| R2#show running-config | section eigrp router eigrp 254 passive-interface default no passive-interface FastEthernet0/0 network 10.0.0.2 0.0.0.0 network 10.0.0.9 0.0.0.0 network 150.2.2.2 0.0.0.0 no auto-summary |
To resolve this issue, modify the configuration on R2 as follows:
| R2(config)#router eigrp 254 R2(config-router)#passive-interface fastethernet 0/0 R2(config-router)#no passive-interface serial 0/0 R2(config-router)#no passive-interface serial 0/1 R2(config-router)#exit |
Solution # 2
The issue is that while R1 and R3 have been configured to use unequal cost load sharing, they have been configured to forward packets using only the lowest metric (cost) path:
| R3#show running-config | section eigrp router eigrp 254 variance 4 traffic-share min across-interfaces passive-interface FastEthernet0/0 network 10.0.0.6 0.0.0.0 network 10.0.0.10 0.0.0.0 network 10.0.0.13 0.0.0.0 network 150.3.3.3 0.0.0.0 no auto-summary |
| R1#show running-config | section eigrp router eigrp 254 variance 4 traffic-share min across-interfaces redistribute static passive-interface FastEthernet0/0 network 10.0.0.1 0.0.0.0 network 10.0.0.5 0.0.0.0 network 150.1.1.1 0.0.0.0 no auto-summary |
To resolve this issue, modify the configuration on these routers as follows:
| R1(config)#router eigrp 254 R1(config-router)#no traffic-share min across-interfaces |
| R3(config)#router eigrp 254 R3(config-router)#no traffic-share min across-interfaces |
Solution # 3
The issue is that the unreachable subnets are not covered in any of the advertised aggregate prefixes. To resolve this, without modifying the EIGRP configuration, do one of two things:
- Configure and advertise a summary route
- Configure and advertise a default route
| R1(config)#ip route 172.30.48.0 255.255.240.0 null 0 |
OR
| R1(config)#ip route 0.0.0.0 0.0.0.0 null 0 |
Solution # 4
The issue is that the clocking has been removed from the Serial1/2 interface on R3. The interface will therefore not come up:
| R3#show controllers serial 1/2 CD2430 Slot 1, Port 2, Controller 0, Channel 2, Revision 19 Channel mode is synchronous serial idb 0x84D4D7D8, buffer size 1524, V.35 DCE cable |
| R4#show controllers serial 0/0 Interface Serial0/0 Hardware is PowerQUICC MPC860 DTE V.35 clocks stopped. |
To resolve this issue, configure R3s Serial1/2 interface to provide clocking:
| R3(config)#interface serial 1/2 R3(config-if)#clock rate 128000 |
Final Working Router Configurations
R1
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R1#term len 0 Current configuration : 1567 bytes R1# |
R2
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R2#term len 0 Current configuration : 954 bytes R2# |
R3
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R3#term len 0 Current configuration : 1362 bytes R3# |
R4
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R4#term len 0 Current configuration : 883 bytes R4# |