How to route only specific subnet (source ip) to a particular interface?

Question

How to route only specific subnet (source ip) to a particular interface?
OS: Linux

I know I can do easily by destination IP by using something like

route add 1.2.3.4/24 dev eth4

but I do not see how can route based on source IP.

score 42 · Accepted Answer · edited Mar 17 '17 at 23:43

You need to use policy based routing. Something kind of like

ip rule add from <source>/<mask> table <name>
ip route add 1.2.3.4/24 via <router> dev eth4 table <name>

<name> is either table name specified in /etc/iproute2/rt_tables or you can use numeric id ...

This pretty much says, that all traffic from 1.2.3.4/24 will be routed using routing table <name>. IIRC it doesen't use the default table after going through this, so if you need other routes (ie. default gateway), you need to add them to the table as well.

score 11 · Answer 2 · edited Jul 16 '14 at 19:02

11

http://wiki.wlug.org.nz/SourceBasedRouting

This site has a nice example of source based routing.

edited Jul 16 '14 at 19:02

Marc

107

answered Jan 11 '12 at 19:05

daya

2,619

score 0 · Answer 3 · answered May 23 '23 at 20:16

0

Another great description how it works:

https://datahacker.blog/industry/technology-menu/networking/routes-and-rules/iproute-and-routing-tables

answered May 23 '23 at 20:16

sredni

109

How to route only specific subnet (source ip) to a particular interface?

3 Answers3

Linked