Information Technology Reference
In-Depth Information
Command Output
Description
C
Source is connected route
172.16.72.0
Third child route
/23
Mask for third child route
FastEthernet0/0
Exit interface for second child route
Routing Table Lookup Process
When a router receives a packet on one of its interfaces, the routing table lookup process compares
the destination IP address of the packet with the entries in the routing table. The best match between
the packet's destination IP address and the route in the routing table is used to determine out which
interface to forward the packet. Just exactly how that happens is the focus of the exercises in the fol-
lowing section.
Complete the Chart
Figure 8-1 shows an incomplete version of the chart used to explain the routing table lookup process.
Write in the correct labels for the chart.
Figure 8-1
Routing Table: Parent/Child Relationship (Answer)
Next-Hop IP Address
and/or Exit Interface
Level 1 Routes
Level 2 Routes
Ultimate
Route
Ultimate
Route
Default
Path/Interface
Supernet
Path/Interface
Ultimate
Route
Network
Path/Interface
Parent Route
Child Route
Ultimate
Route
Network
Subnet
Path/Interface
Ultimate
Route
Subnet
Path/Interface
Routing Table Lookup Exercise
The routing table shown in Example 8-3 will be used in this exercise.
Example 8-3
Routing Table for B2
B2#
show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
<output omitted>
continues
