5.7.2 - Default Route and Routing Loop Issues

Flashcards covering default routes, routing loops, and prevention mechanisms.

Default Gateway

A gateway that each end host must be configured with to communicate with remote hosts.

Default Route

An entry in the host's routing table for 0.0.0.0/0 that uses the router's IP address as the path.

Default Gateway Address

Verify you can ping this address if the host cannot contact remote networks.

Router Issues Impact

A faulty router configuration or a router/interface being down likely results in connectivity problems for multiple hosts.

Default Routes (Router)

Misconfigured or propagating these to other routers can cause routing loops.

Routing Loop

Occurs when two routers use one another as the path to a network.

Routing Loop Behavior

Packets caught in this continue circling until the TTL expires.

Potential Routing Loop

Routers generating ICMP Time Exceeded error messages are a symptom of this.

Maximum Hop Count

If the cost exceeds a certain value (16 in RIP), the network is deemed unreachable.

Poison Route

A route advertised with a hop count of 16; provides explicit failure notice.

Holddown Timer

Neighbors start this if a node declares a network unreachable; updates are discarded for the timer's duration.

Split Horizon

Prevents a routing update from being copied back to the source.

Link State Protocols

Ensures each node has a consistent view through timely updates flooded to all nodes.

Traceroute

Can be used to diagnose a routing loop by looking for IP addresses that appear multiple times.