Page 1 of 2 12 LastLast
Results 1 to 10 of 15

Thread: Problem with multiple NIC's on server

  1. #1
    Join Date
    Oct 2007
    Location
    Vanløse, Denmark
    Beans
    39
    Distro
    Ubuntu 12.10 Quantal Quetzal

    Question Problem with multiple NIC's on server

    Hi guys!


    I'm in a bit of a pickle here and I really hope you can help me.
    I'm running Ubuntu Server 11.10 on a server with 4 Ethernet ports.

    I've configured two static IP addresses on two different Ethernet ports.

    My /etc/network/interfaces looks like this:
    Code:
    auto lo
    iface lo inet loopback
    
    # The primary network interface
    iface eth0 inet static
    	address 192.168.113.18
    	netmask 255.255.255.0
    	broadcast 192.168.113.255
    	network 192.168.113.0
    	gateway 192.168.113.254
    
    iface eth1 inet static
    	address 192.168.113.19
    	netmask 255.255.255.0
    	broadcast 192.168.113.255
    	network 192.168.113.0
    Now, my problem is kind of weird.
    When I ping 192.168.113.18 I get a response. When I ping 192.168.113.19 I get a response.
    1. If I pull the Ethernet-cable out of eth0 while eth1 still being connected, both .18 and .19 is unresponsive.
    2. If I pull the Ethernet-cable out of eth1 while eth0 still being connected, I still get a response from both .18 and .19.


    What can this be?

    *The attached interfaces.txt file is the original interfaces file. I stripped it down to only eth0 and eth1 for testing this weird behaviour.
    Attached Files Attached Files
    Last edited by knutz; January 5th, 2013 at 10:29 PM.

  2. #2
    Join Date
    Aug 2010
    Beans
    27

    Re: Problem with multiple NIC's on server

    What do you get when you run 'route'. I think you'll find that eth0 is acting as a gateway for anything 192.168.113.* So if eth0 is down it won't be able to do anything - as you've found.

  3. #3
    Join Date
    May 2006
    Location
    Milwaukee,WI
    Beans
    5,926
    Distro
    Xubuntu 12.04 Precise Pangolin

    Re: Problem with multiple NIC's on server

    in order to help I think we need to know what you're trying to accomplish with all 4 of these NICs
    Check out my Blog about my life and computer software and hardware. http://ubuntuaddicted.blogspot.com/
    My YouTube channel:
    http://www.youtube.com/ubuntuaddicted

  4. #4
    Join Date
    Oct 2007
    Location
    Vanløse, Denmark
    Beans
    39
    Distro
    Ubuntu 12.10 Quantal Quetzal

    Re: Problem with multiple NIC's on server

    Quote Originally Posted by NigelRen View Post
    What do you get when you run 'route'. I think you'll find that eth0 is acting as a gateway for anything 192.168.113.* So if eth0 is down it won't be able to do anything - as you've found.
    The output of route is:
    Code:
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    default         192.168.113.254 0.0.0.0         UG    100    0        0 eth0
    192.168.113.0   *               255.255.255.0   U     0      0        0 eth0
    192.168.113.0   *               255.255.255.0   U     0      0        0 eth1

  5. #5
    Join Date
    Oct 2007
    Location
    Vanløse, Denmark
    Beans
    39
    Distro
    Ubuntu 12.10 Quantal Quetzal

    Re: Problem with multiple NIC's on server

    Quote Originally Posted by dannyboy79 View Post
    in order to help I think we need to know what you're trying to accomplish with all 4 of these NICs
    Well. I want eth0 to have the address 192.168.113.18 and eth1 to have the address 192.168.113.19.
    As it is now, both IP addresses is on the NIC eth0.

  6. #6
    Join Date
    May 2006
    Location
    Milwaukee,WI
    Beans
    5,926
    Distro
    Xubuntu 12.04 Precise Pangolin

    Re: Problem with multiple NIC's on server

    why would you want the same computer to have 2 IP's from the same subnet? just curious, trying to understand your end goal
    Check out my Blog about my life and computer software and hardware. http://ubuntuaddicted.blogspot.com/
    My YouTube channel:
    http://www.youtube.com/ubuntuaddicted

  7. #7
    Join Date
    Oct 2007
    Location
    Vanløse, Denmark
    Beans
    39
    Distro
    Ubuntu 12.10 Quantal Quetzal

    Re: Problem with multiple NIC's on server

    Quote Originally Posted by dannyboy79 View Post
    why would you want the same computer to have 2 IP's from the same subnet? just curious, trying to understand your end goal
    In the original setup:
    Well, the Server serves as a multi-user VirtualBox environment. All the users have a VirtualBox instance. Each of these users have a tap interface which is bridged to eth2. The virtual machines serves as workstations for each user.
    eth1 serves all the virtual servers.
    All traffic through eth0 is the RDP connections to each workstation and the VirtualBox webserver.

    In the test setup:
    So, I want all the RDP connection- and web-traffic on one NIC and all the Virtual Machine traffic on another. Even though they are on the same network.

  8. #8
    Join Date
    May 2006
    Location
    Milwaukee,WI
    Beans
    5,926
    Distro
    Xubuntu 12.04 Precise Pangolin

    Re: Problem with multiple NIC's on server

    ok, wow, this is way over my head. sorry can't help. lol
    Check out my Blog about my life and computer software and hardware. http://ubuntuaddicted.blogspot.com/
    My YouTube channel:
    http://www.youtube.com/ubuntuaddicted

  9. #9
    Join Date
    Aug 2010
    Beans
    27

    Re: Problem with multiple NIC's on server

    Quote Originally Posted by knutz View Post
    The output of route is:
    Code:
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    default         192.168.113.254 0.0.0.0         UG    100    0        0 eth0
    192.168.113.0   *               255.255.255.0   U     0      0        0 eth0
    192.168.113.0   *               255.255.255.0   U     0      0        0 eth1
    Which is what I was saying - eth0 is your main route out.

    OK - so what are you trying to achieve by unplugging the cables? Is this just curiosity or are you trying to achieve something with it?

  10. #10
    Join Date
    Nov 2007
    Location
    Newry, Northern Ireland
    Beans
    1,192

    Re: Problem with multiple NIC's on server

    Quote Originally Posted by knutz View Post
    In the original setup:
    Well, the Server serves as a multi-user VirtualBox environment. All the users have a VirtualBox instance. Each of these users have a tap interface which is bridged to eth2. The virtual machines serves as workstations for each user.
    eth1 serves all the virtual servers.
    All traffic through eth0 is the RDP connections to each workstation and the VirtualBox webserver.

    In the test setup:
    So, I want all the RDP connection- and web-traffic on one NIC and all the Virtual Machine traffic on another. Even though they are on the same network.
    Could you explain the reasoning behind this a little further? Is it because of bandwidth reasons on each interface? If it is, another solution would be to use Link Aggregation to bond several interfaces into one bonded interface capable of greater bandwidth. It does require a LA capable switch, but most enterprise switches are.
    Can't think of anything profound or witty.
    My Blog: http://gonzothegeek.blogspot.co.uk/

Page 1 of 2 12 LastLast

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •