are you supposed to use both NICs on a linux server?

Question

this may sound ridiculous, but i'm really not sure whether to use the 2nd NIC on a linux server. what do you do with your 2nd NIC? is it for redundancy or for throughput? on our mail server (postfix), we're very confused as to what is the optimal use of that 2nd NIC. thanks so much!

Answer 1

If you had a separate internal-only network, for security, you could use the second port for that. For example, if the link between your web server and database server was on an isolated network which your web server(s) had exclusive access to, this is where a second NIC would come in handy.

Answer 2

There is also NIC TEAMING, I think it's called Ethernet Bonding or Trunking on Linux, for redundancy or increased throughput.

Answer 3

Security is pretty tight where I work, and individual departments have their own subnets. My department has three subnets of its own. Several machines are shared between groups. The NICs on these machines (up to four at the moment) plug into each network, but a lot of the machines never use their second port (let alone ports three and four).

I also use some machines as jumphosts. That is a machine that runs nothing but sshd and is attached to two or more networks. The only way to get from a machine on network A to a machine on network B is to connect to a jumphost that is in both networks and the ssh from there to the machine on network B.