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sandoz
Asked: 2010-10-08 06:21:47 +0800 CST

How to see on Linux what network interface and source IP address is used for a route to a specific destination host?

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If I have multiple network interfaces (here: 2) on a Linux machine (here: Debian Lenny). How do I see, over what network interface (NIC) a route to a specific destination host is going and what source IP address is used by default?

I have though of using

ping -I nic1 desthost.example.com
ping -I nic2 desthost.example.com

too see if both ways are possible. (Here: Both ways are possible)

I looked up the routing table

ip route show

But it's quite complex, so I thought, there must by a small simple tool, to just tell me:

"To destination host desthost.example.com it takes interface nicX and source IP address 10.0.0.1"

What is the simplest way of getting this information?

(And I'd rather not use tcpdump and set the interfaces in promiscous mode.)

Thanks.

linux networking linux-networking

4 Answers

  1. Best Answer

    Use ip route get <ip>.

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  2. what about route -C

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  3. I use netstat -Wcatnp . You should try this command.

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  4. Even easier, I'd say nm-tool and if you only want the relevant line nm-tool | grep Device. That should output:

    - Device: wlan0  [My router name] -----------------------------------------------
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