Multiple NICs in server

Discussion in 'Server Networking' started by Jeremey, Mar 14, 2005.

  1. Jeremey

    Jeremey Guest


    we have three servers that all have three NICS in them. One NIC in each is
    going to the main network the others are being crossed over to the other
    servers for doing file pulls so that it doesn't affect the rest of the
    network. One thing we noticed is that with all three NIC's up and connected
    the response times on the network when connecting to any of the servers are
    greatly degraded. By removing the cross connects everything speeds up.

    Any thoughts?

    Jeremey, Mar 14, 2005
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  2. Jeremey

    Matt Gibson Guest

    Use switches :)

    Don't do full-mesh networking through crossover cables.

    Try going down to two NICs in each server, with the second nic connected to
    a server only switch.

    Without more information about traffic levels and such, I can't suggest much

    Matt Gibson - GSEC
    Matt Gibson, Mar 14, 2005
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  3. I would even go so far as to say one nic in each. The machine won't even
    use the other nics in most cases because the host name of the machine will
    only resolve to one IP#.
    Phillip Windell, Mar 14, 2005
  4. Jeremey

    Matt Gibson Guest

    Agreed, but one could use custom routing tables to override such behavior.

    Matt Gibson - GSEC

    Matt Gibson, Mar 14, 2005
  5. Yea, as long as IP#s were used to specify the target instead of any "names".
    Or I guess a guy could create fake static Names in WINS (or DNS) and assign
    IP#s to those names, then use those names as the "target".


    Phillip Windell [MCP, MVP, CCNA]

    Phillip Windell, Mar 14, 2005
  6. Jeremey

    Matt Gibson Guest


    Either way, it's not something I'd want to do.

    I fully agree with your original point, if you can get away with one NIC,
    then use one NIC.

    Matt Gibson - GSEC

    Matt Gibson, Mar 14, 2005
  7. Jeremey

    Mr. Smith Guest

    * PFFFFFT*

    Let's say he wants to just do secure file transfers on another network other
    than the one he's on. I would like to shape some traffic in my case and use
    the 2nd NIC's to have a file sharing / printer network. This network would
    be on a switch to itself for many of things, such as using SNMP in a secured
    network that doesn't traverse other data; this would limit anyone sniffing
    out data that is being transferred over the main user network.

    A network isn't the machines / OSes that are on it. It's the network.

    You want to build your network(s) first then put your machines on it.

    Crazy Example

    ((INTERNET)) -to- (FIREWALL)) -to- ((DMZ)) -to- ((ROUTER)) -to-

    (SWITCH 01)

    (SWITCH 02)

    (SWITCH 03)

    And so on. Each of these switches will be a network to them self:
    Mr. Smith, Mar 14, 2005
  8. Jeremey

    Matt Gibson Guest

    I don't get what you're getting at.

    Yes, sometimes two NICs are needed. In your case, an argument could be made
    that using two NICs isn't secure, because that server could potentially act
    as a bridge between two different security zones.

    And the OP in question doesn't want to do what you stated, so I don't see
    your point.

    Matt Gibson - GSEC
    Matt Gibson, Mar 14, 2005
  9. I don't answer the posts on what they might want to. I try to answer based
    on what is best for what they a specifically doing. Yes, there are
    situations when multiple NIC are legitiment, but in my experience in these
    group my rough guess is that only about 10% of the "multi-Nic" questions
    have to do with legitiment situations for do doing such.
    Phillip Windell, Mar 15, 2005
  10. Jeremey

    Jeremey Guest

    Hi Guys,

    Thanks for your help. Just so you know the only reason we were doing this
    is to replicate data between the servers and not affect the rest of our
    network with the overhead. So we were setting up batch files to copy from
    the production server to the test and backup server via IP on the second nic
    not by Server name. Where what we noticed is, a specific application that
    runs on the production server was impacted by slow response time, and once we
    disconnected the cable between the two servers, everything was running at
    optimal speeds. So from the first post after my original, do you all agree
    that running these with a Switch between them rather than a cross over would
    change the response issue or no?

    Thanks again,


    Jeremey, Mar 15, 2005
  11. Jeremey

    Matt Gibson Guest

    Well, have you tried it yet? *grin*

    If you've got gigabit network cards in the servers, and a good switch, I
    can't see it really affecting the clients too badly...depends on how much
    data you're moving, and how often.

    If you're trying to move say 20GB, and the hardware on both servers can feed
    it fast enough, then that might slow everything down, since your NIC will be
    saturated. However, in all my experiences, I can do huge file copies, and
    the NIC won't saturate, meaning no clients see a difference.

    Matt Gibson - GSEC

    Matt Gibson, Mar 15, 2005
  12. I think you should just forget it and use the one NIC. If you used a Switch
    instead of HUBs (sounds like you are) then the Switch already isolates the
    traffic so that only the involved machines even see it. Switches create
    isolated "virtual circuits" between communicating Hosts,...that is their

    There is very little chance that your "replication" is going to saturate
    anything,..and even if it did you would only have to replace the Nics and
    the Switch with Gigabit units, while running 100mbps from that Switch to the
    rest of the network.


    Phillip Windell [MCP, MVP, CCNA]

    Phillip Windell, Mar 15, 2005
  13. Hmm....I didn't read your post until I sent mine....looks like we're both
    telling him the same thing,...again :)


    Phillip Windell [MCP, MVP, CCNA]

    Phillip Windell, Mar 15, 2005
  14. Jeremey

    Matt Gibson Guest

    Quick, I'll start telling him to add a fourth NIC in...that way you look
    better. The whole Good cop bad cop thing. :)

    Matt Gibson - GSEC

    Matt Gibson, Mar 15, 2005
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