System information

Troubleshooting TCP/IP
Book Title
7-118
Subnet mask mismatch Problems occur when two or more interfaces on the same major network have
different subnet masks configured.
Step 1 Use the show running-config privileged exec command to view the
configuration of each router in the major network.
Step 2 Use the show ip interface privileged exec command. Check the subnet
mask specified for each interface. There is a subnet mask mismatch if two
or more interfaces on the same major network have different subnet
masks.
Step 3 If two interfaces on the same network have different subnet masks, you
must change the subnet mask specification for one of the interfaces using
the ip address ip-address mask interface configuration command (or use
a classless routing protocol such as OSPF or Enhanced IGRP).
For example, to configure Ethernet interface 1 with the IP address
192.168.52.46 using a subnet mask of 255.255.255.0, enter the following
commands:
C4000(config)#interface e1
c4000(config-if)#ip address 192.168.52.46 255.255.255.0
For more information about subnet masks, see the section “Host and Router
Subnet Mask Mismatch Example” later in this chapter.
Missing default-metric
command
This problem is restricted to environments in which route redistribution is being
performed between autonomous systems or between multiple routing protocols.
Step 1 Use the show running-config privileged exec command on suspect
routers. Look for default-metric router configuration command entries.
This command assigns default metric values to redistributed routes.
Step 2 IGRP requires a default-metric parameter to redistribute routes. If you are
running IGRP, define the default metrics for redistributed routes using the
default-metric router configuration command.
The following example shows a configuration that redistributes RIP
routes and assigns them IGRP metrics with values as follows:
bandwidth = 1000, delay = 100, reliability = 250, loading = 100, and
mtu = 1500:
router igrp 109
network 131.108.0.0
redistribute rip
default-metric 1000 100 250 100 1500
Step 3
If you are running RIP, you do not have to configure a default metric in
order to redistribute routes. By default, the metric assigned to all routes
redistributed into RIP is 1. However, this value can be changed using the
default-metric command.
If a default-metric statement that is applied to RIP appears in the
configuration, make sure that the metric value it assigns will not adversely
affect network performance. If you are unsure, restore the default value
for the routing metric using the no default-metric router configuration
command.
For more information on the default-metric router configuration command, see
the Cisco IOS configuration guides and command references.
Possible Problem Solution