Find interface for route to specific host

Question

On a multihomed Linux machine, how can I find out what network interface will be used to send a packet to a specific host? I need to do this programmatically and I'd rather not parse and interpret the routing table myself.

That's what routing table is for. I don't imagine it otherwise. — GioMac, Aug 17 '13 at 18:02

score 51 · Accepted Answer · answered Aug 17 '13 at 18:03

51

Use ip route for this. For instance:

ip route show to match 198.252.206.16

answered Aug 17 '13 at 18:03

Michael Hampton

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score 34 · Answer 2 · edited Jul 26 '18 at 00:06

34

Shorter option:

ip route get 172.29.42.94

edited Jul 26 '18 at 00:06

davidparks21

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answered Nov 17 '14 at 15:03

Alexey

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score 7 · Answer 3 · answered Jul 06 '14 at 13:42

Yes, as Michael Hampton suggests, use ip route. If you only want the interface, use this

ip -o route get $ip | perl -nle 'if ( /dev\s+(\S+)/ ) {print $1}'

For example:

# ip=8.8.8.8
# iface=$( ip -o route get $ip | perl -nle 'if ( /dev\s+(\S+)/ ) {print $1}' )
# echo $iface
eth1

Find interface for route to specific host

3 Answers3

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