This section discusses several possible scenarios that can prevent routes
from being installed in the routing table.
Missing routes in the routing
table create reachability problems. Users start complaining that they cannot
reach a server or a printer. When this problem is investigated, one of the
first things to look for is if the appropriate routers have a route for this
destination in their routing tables.
Three possibilities exist for
routes not being installed in the routing table:
Receiver problem – The router is receiving the updates, but it is not
installing the routes.
Intermediate media problem, Layer 2 – The sender has sent the updates, but
they were lost along the way and the receiver did not receive them.
Sender problem – The sender is not advertising the routes, so the receiving
side is not seeing the routes in the routing table.
Some of the common causes for routes not being installed in the routing
table are:
Missing or incorrect network or neighbor statement
Lab
Exercise: Troubleshooting Problems at the Physical, Data Link, and Network
Layers II
After completing this lab, the student will be able to follow a
logical troubleshooting process to define, isolate, and correct problems
outlined in a trouble ticket.