ACIM Personal Knowledgebase

This page is read only. You can view the source, but not change it. Ask your administrator if you think this is wrong.
====== Two default gateways on Linux ======

===== Two default gateways on CentOS =====


You have two or more network cards (interfaces) in one Linux system and each of these interfaces has its own default gateway. By default, you can only have one default gateway on a system.

We assume that we have two interfaces:

<code bash>
eth0
eth1
</code>

Two networks that should be used are:

<code bash>
192.168.1.0/24
10.10.0.0/24
</code>

whereby the first IP address in each respective network should be the gateway. Config files for these interfaces are in

<code bash>
/etc/sysconfing/network-scripts/ifcfg-eth0
</code>

and

<code bash>
ifcfg-eth1
</code>

and it looks like this:

<code bash>
# cat /etc/sysconfig/network-scripts/ifcfg-eth0
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=no
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME=eth0
UUID=7f164bfd-1ae4-4062-aadd-e2ea8bc0121e
DEVICE=eth0
ONBOOT=yes
IPADDR=192.168.1.5
PREFIX=24
GATEWAY=192.168.1.1
DNS1=8.8.8.8
DNS2=1.1.1.1
</code>

<code bash>
# cat /etc/sysconfig/network-scripts/ifcfg-eth1
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
IPADDR=10.10.0.124
PREFIX=24
DNS1=8.8.8.8
DNS2=1.1.1.1
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=no
NAME=eth1
UUID=9320b706-e68e-3610-9fec-9988316bd478
DEVICE=eth1
ONBOOT=yes
GATEWAY=10.10.0.1
NETMASK=255.255.255.0
NM_CONTROLLED=yes
</code>

To use a second interface and address we need to add another routing table. To do this go to file:

<code bash>
# vim /etc/iproute2/rt_tables
</code>
and add at the end “1 rt2”:

<code winbatch>
#
# reserved values
#
255     local
254     main
253     default
0       unspec
#
# local
#
#1      inr.ruhep
1 rt2
</code>

Now we need to add routing rules and routes:

<code bash>
# ip route add default via 10.10.0.1 dev eth1 table rt2
# ip rule add from 10.10.0.0/24 table rt2
</code>

You can check these changes with commands:

<code bash>
# ip route show table rt2
# ip rule show
</code>
ACIM Personal Knowledgebase

User Tools

Site Tools

Page Tools
