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"Only enable one NIC if More Than One NIC on Server" - Why? RRS feed

  • Question

  • In "Troubleshooting Windows Home Server 2011 Installation", step 3. "If you have more than one Netork Interface Card (NIC) on the server, verify that only one NIC is enabled."  Why?  I don't have any issues, but am concerned if this affects performance in any way.  The server is an Intel S3420GP, which has two NICs.  I do not use the server as a firewall and nothing is connected to one NIC.  Does it matter which NIC is enabled and used? Does it only matter at installation of WHS?  Even if everything is working, should I now disable one NIC? 


    • Edited by steve1916 Sunday, September 25, 2011 7:45 AM
    Sunday, September 25, 2011 7:40 AM

Answers

  • Because a disconnected NIC can cause installation to fail, and because which NIC will be used as primary is difficult to determine. Since Windows in general doesn't make efficient use of multiple NICs, the easiest thing to do is just disable one completely.
    I'm not on the WHS team, I just post a lot. :)
    • Proposed as answer by Theo van Elsberg Monday, September 26, 2011 9:27 AM
    • Marked as answer by steve1916 Thursday, September 29, 2011 4:33 AM
    Sunday, September 25, 2011 3:01 PM
  • I've been searching and found that it somewhat depends on the components involved.  Everything you say is true and there are more uses for two NICs and more component configurations than I imagined, so a conservative approach is the best advice.  In my particular case, the two NICs are built into the motherboard.  This particular design has a default NIC, so by selecting NIC 1 for my network I was lucky and probably avoided an installation failure because NIC 1 is primary by default.

    I'm sure there are other motherboard designs and there could be many different combinations of integrated and plugin NICs.  My thought was to disable NIC2 in the BIOS, but it's not clear if that's possible.  The technical specification for the motherboard says there is a NIC 2 ROM and disabling it means NIC 2 cannot be used to boot or wake the system, so the NIC may not be disabled completely in the BIOS.

    In Windows 7 the NICs are identified by adapter name, not NIC number, so it took some searching to determine which adapter was NIC1.  I found that if you do properties on the NIC (in Device Manager) then look under the Link Speed Tab and then click the Identify Adapter button, a flashing light on the NIC connector will identify the physical location of the adapter.  Someone with experience working with larger networks would have known this.

    Finally it looked like I could or should disable NIC 2 in Windows to avoid the issue of mistakenly plugging the ethernet cable into the wrong adapter. So, I moved the cat 6 cable to NIC 2 to see what would happen.  When I clicked on Dasboard in the Launchpad, I re-discovered that the NICs are assigned different IP addresses (Duh!) "Unable to connect to your server."  and "To retry connecting using your server's last known IP address (nnn.nnn.n.nnn), click OK."  There is a subtle hint here as there was no offer to discover or input a new IP address.  So this kind of makes  the system "idiot proof".  If I were to shut down the server and all computers and the router, then boot up again, I suspect it might work with this hardware and some, but not all, other hardware.   At this point it's just not worth more time to learn by trial and error.



    • Edited by steve1916 Thursday, September 29, 2011 4:31 AM
    • Marked as answer by Ken Warren Thursday, September 29, 2011 12:54 PM
    Thursday, September 29, 2011 4:22 AM

All replies

  • Because a disconnected NIC can cause installation to fail, and because which NIC will be used as primary is difficult to determine. Since Windows in general doesn't make efficient use of multiple NICs, the easiest thing to do is just disable one completely.
    I'm not on the WHS team, I just post a lot. :)
    • Proposed as answer by Theo van Elsberg Monday, September 26, 2011 9:27 AM
    • Marked as answer by steve1916 Thursday, September 29, 2011 4:33 AM
    Sunday, September 25, 2011 3:01 PM
  • I've been searching and found that it somewhat depends on the components involved.  Everything you say is true and there are more uses for two NICs and more component configurations than I imagined, so a conservative approach is the best advice.  In my particular case, the two NICs are built into the motherboard.  This particular design has a default NIC, so by selecting NIC 1 for my network I was lucky and probably avoided an installation failure because NIC 1 is primary by default.

    I'm sure there are other motherboard designs and there could be many different combinations of integrated and plugin NICs.  My thought was to disable NIC2 in the BIOS, but it's not clear if that's possible.  The technical specification for the motherboard says there is a NIC 2 ROM and disabling it means NIC 2 cannot be used to boot or wake the system, so the NIC may not be disabled completely in the BIOS.

    In Windows 7 the NICs are identified by adapter name, not NIC number, so it took some searching to determine which adapter was NIC1.  I found that if you do properties on the NIC (in Device Manager) then look under the Link Speed Tab and then click the Identify Adapter button, a flashing light on the NIC connector will identify the physical location of the adapter.  Someone with experience working with larger networks would have known this.

    Finally it looked like I could or should disable NIC 2 in Windows to avoid the issue of mistakenly plugging the ethernet cable into the wrong adapter. So, I moved the cat 6 cable to NIC 2 to see what would happen.  When I clicked on Dasboard in the Launchpad, I re-discovered that the NICs are assigned different IP addresses (Duh!) "Unable to connect to your server."  and "To retry connecting using your server's last known IP address (nnn.nnn.n.nnn), click OK."  There is a subtle hint here as there was no offer to discover or input a new IP address.  So this kind of makes  the system "idiot proof".  If I were to shut down the server and all computers and the router, then boot up again, I suspect it might work with this hardware and some, but not all, other hardware.   At this point it's just not worth more time to learn by trial and error.



    • Edited by steve1916 Thursday, September 29, 2011 4:31 AM
    • Marked as answer by Ken Warren Thursday, September 29, 2011 12:54 PM
    Thursday, September 29, 2011 4:22 AM