A Red Hat Enterprise Linux system should have a single default gateway defined. However, sometimes, it does occur that a system has multiple default gateways. Here's information to detect multiple default gateways and how to get rid of them:

First, check the number of default gateways defined, by running the netstat command and looking for entries that start with 0.0.0.0:

# netstat -nr | grep ^0.0.0.0
0.0.0.0     192.168.0.1     0.0.0.0    UG        0 0        0 em1
0.0.0.0     192.168.1.1     0.0.0.0    UG        0 0        0 em2

In the example above, there are 2 default gateway entries, one to 192.168.0.1, and another one to 192.168.1.1.

Quite often, more than 1 default gateways will be defined on a RHEL system, if there are multiple network interfaces present, and a GATEWAY entry is defined in each of the network interface files in /etc/sysconfig/network-script/ifcfg-*:

# grep GATEWAY /etc/sysconfig/network-scripts/ifcfg-*
ifcfg-em1:GATEWAY=192.168.0.1
ifcfg-em2:GATEWAY=192.168.1.1

On a system with multiple network interfaces, it is best to define the default gateway in file /etc/sysconfig/network instead. This file is global network file. Put the following entries in this file, assuming your default gateway is 192.168.0.1 and the network interface to be used for the default gateway is em1:

GATEWAY=192.168.0.1
GATEWAYDEV=em1

Next, remove any GATEWAY entries in any of the ifcfg-* files in /etc/sysconfig/network-scripts.

Finally, restart the network service:

# service network restart

This should resolve multiple default gateways, and the output of the netstat command should now only show one single entry with 0.0.0.0.

Note: If the netstat command is not available on the system, you may also determine the number of default gateways, by running:

# ip route show | grep ^default

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