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PC with dual NICs question.

I have a hypothetical question.

RFC1180 sec2.4 deals with a PC that has dual NICs.

What would happen if I configured both interfaces within the same network/subnet and DISABLED IP forwarding (no routing on say bsd or linux).

What would the implications of this scenario be. Any links, suggestions would be welcome.

Please do not change the scenario in order to answer the question. I'm aware that ideally both interfaces should be in a separate network.

1 REPLY
Green

Re: PC with dual NICs question.

There is no issue wth having two (or more) interfaces in the same net/subnet, as long as they have different host addresses.

You don't need to disable forwarding, routers will not route to the same net/subnet.

If the interfaces are not teamed (i.e., left at the default functionality, not "joined" for bandwidth multiplication or redundancy) then one will handle most (if not all) of the outbound traffic, and inbound traffic can be aimed at a specific interface.

For example, int1 @ 192.168.1.1 and int2 @ 192.168.1.2.

Int1 would be used as the general I/O.

Int2 could be used as the address of a web service, with the web service configured / bound to only that interface.

The drawback to this kind of configuration relates to security issues. Having an interface to the outside *and* and interface to the inside without some sort of firewall process and a buttload of filters and blocks enabled can provide an easy access for hackers. Exploits still pop up now and then for even the most locked-down web servers.

If your intention is to team the interfaces for bandwidth or redundancy, you will also need a switch configurable for the compatible protocol (like spanning tree or Etherchannel/LACP).

Good Luck

Scott

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