Pinging IP located on another interface

Applications IP Networking
1

Hi,

I have a rather strange IP question...

Here's my problem:

  • I have a Linux box (call it "turing") with 2 NICs.
  • One network interface (eth0) has an IP assigned, say 192.168.42.50.
  • The other interface (eth1) is up, but has no IP yet.

My question: is it possible to determine from another computer connected to eth1 per ICMP echo request that the IP 192.168.42.50 is already assigned to my box "turing"? IOW:

  • the ICMP Echo request comes from eth1
  • the IP asked in the request is assigned to eth0
  • What I'd want to achieve: turing sends ICMP reply through eth1.

I am not sure if that's make any sense, or is possible...

You may wonder why on the earth I'm trying to solve such a twisted problem... It's a epic story... But in essence that is the problem (shaved to the bone) I need to solve for some new use cases of a system with bad architecture that I can't fix because it would break compatibility with other systems :wall:

Thanks,
/NH2

2

Simple answer: no.

Longer answer: The hosts connected to eth1 won't even know it's there, because without an IP it won't send a ARP announce, or react to an ARP request, which is needed to get the destination MAC address. In a switched environment the port it's connected to probably would even be ignored (except maybe for Ethernet broadcasts).

3

a> pludi is correct.

b> If you explain what you're trying to do, one of us might have an idea as to how to achieve it. e.g. Is there a certain kind of service you're trying to run? are you trying to reach some certain level of performance? Is there something about your network topology that leads you to feel that in one interface and out the other would be crucial or superior?

4

I think That I understand the question being asked by NH2.

There's a system with two interfaces A and B connected to A and B LAN's. Interface A is up and working with an ip address and LAN A users can access it.

Interface B is down (no ip address) but is there a way that LAN B users could be told (by enquiring on the MAC address or something) that the system has an alternative address on LAN A (assuming of course that there is a gateway between LAN A and LAN B that they could go through).

The only answer that I can think of (and I'm not a networking guru) is, yes, let them call for the system by name and use a DNS server.