Chapter 12: Troubleshooting Redistribution Routing Environments

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Overview

Redistribution among routing protocols is common in the current networking environment. You need to configure redistribution in scenarios such as mergers and acquisition of companies, which might require combining diverse networks, expanding step by step, or incorporating equipment from multiple vendors.

Redistribution leads to sharing routing information among various routing protocols, a phenomenon that does not happen by default. The routing tables become more complex after incorporating redistribution. As a result, redistribution requires detailed study of the network, careful planning, and proper decision on the points of redistribution and the routes to be redistributed. The common problems due to redistribution are:

Probable routing loops: Arise due to inconsistencies in the routing states of different routers present in an interconnected network. These loops result in packet loss and delays in packet transmission.

Nonoptimal path selection: In the case of an optimal routing system, the path through which data traverses is considered the best available path. This path is selected by routers to achieve faster data packet delivery. In the case of nonoptimal path selection, the data delivery time will be longer, resulting in delay and less network performance.

To prevent problems related to redistribution, use route maps and distribution lists in order. There are no generic Cisco IOS commands to troubleshoot all types of redistribution scenarios. For troubleshooting redistribution related issues, a thorough understanding of the network is a primary requirement. The commands used in troubleshooting redistribution problems are generic IP routing-related commands, such as show ip route, show ip interface, show interface, show ip protocols, show running-configuration, ping, and traceroute.

Later in the chapter we will discuss different redistribution scenarios, problems that can arise in them, and ways to troubleshoot the problems.