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  1. #1
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    How can I setup Dual NIC cards for extra redundancy?

    Hi,

    I have linux dedicated server and like to setup dual NIC cards for extra redundancy.. in case one NIC card fails.

    I have no idea how I can set this up..how can I do this? I understand at least I need swtich.. and?

    Please advise on it.

    thanks

  2. #2
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    I have linux dedicated server and like to setup dual NIC cards for extra redundancy.. in case one NIC card fails.
    the chance of a NIC failing are slim to none. You're better off worrying about hard hard drives and boards/processors failing as THAT is the key worry

    If your NIC fails, it's a 5 minute replacement. It's almost guaranteed that your DC will have an extra NIC around, and they will happily replace that.

    As far as redundancy:
    You can't have multiple NIC's running the same ip address. IP's are bound to the NIC, so if NIC 1 goes down, NIC 2 may still be intact, but it will be intact under a DIFFERENT ip address, one that you must assign to it.

    In short, you'll NEVER get dual NIC's to run redundantly. It's just not possible. You CAN assign the server base ip to one nic, and the other ip's to the other nic, but that's not the same, and it certainly isn't "redundancy".
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  3. #3
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    I am certainly not a linux guru, but taking from this link: http://64.233.167.104/search?q=cache...s&ct=clnk&cd=1

    Bonding two nic's to the same IP is an easy process. This is taken from
    the bonding.txt file.

    1) create a bond0 file in your /etc/sysconfig/network-scripts directory

    DEVICE=bond0
    IPADDR=192.168.1.1
    NETMASK=255.255.255.0
    NETWORK=192.168.1.0
    BROADCAST=192.168.1.255
    ONBOOT=yes
    BOOTPROTO=none
    USERCTL=no

    2)add an entry into your /etc/modprobe.conf file

    Alias bond0 bonding

    3) Change your /etc/sysconfig/network-scripts/ifcfg-eth0 file to
    DEVICE=eth0
    USERCTL=no
    ONBOOT=yes
    MASTER=bond0
    SLAVE=yes
    BOOTPROTO=none

    4)Change your /etc/sysconfig/network-scripts/ifcfg-eth1 file to
    DEVICE=eth1
    USERCTL=no
    ONBOOT=yes
    MASTER=bond0
    SLAVE=yes
    BOOTPROTO=none

    Restart network
    *edit*

    And a bit better link here: http://www.redhat.com/docs/manuals/e...NTERFACES-CHAN
    Last edited by dollar; 01-10-2007 at 10:28 AM.
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  4. #4
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  5. #5
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    Dollar, so with just that, can do redundancy on NIC? simple?

  6. #6
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    You may also want to look into LVS http://www.linuxvirtualserver.org/ if you need something with more features.

    Which ever you choose, I would make sure you're host doesn't have a problem with you doing a setup like that (i.e. two network cards from the same machine on the same layer 2 area using the same ip address). If they've designed things well it shouldn't matter but its better to be safe then sorry.

    Note: Bonding / Trunking normally requires the assistance of the hosting provider and changes made to the access switch you're connected to. Most network gear requires you to be on the same switch in order to bond two (or more) switch ports together. However something like LVS (or VRRP etc.) will allow you to be on different switches (assuming things are configured properly) which will give you an added layer of redundancy.
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  7. #7
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    Dual NIC teaming can be utilized. I'm not sure of the config for linux boxes but in windows you have a couple of choices. One setup is aggregated where it is failover redundancy, should one card fail the other takes over. You can also team the NICs so that one is used purely for upload/outbound traffic while the other is used for download/inbound traffic. If windows can do it I am sure theres a Linux setup similar to this. Load balancing can also achieve 200Mbps up if 2 NIC are teamed to use both up and down each on a 100Mbps port.

    The switch must support this config though and has to be specified at the port level within the switch.

    Cisco's I believe need support of at least 802.q . I think that was the version. It's been a long time since I did the reading up on it as it's not something we need.
    Last edited by Patrick67; 01-10-2007 at 01:05 PM.

  8. #8
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    Quote Originally Posted by iHubNet
    Dollar, so with just that, can do redundancy on NIC? simple?
    To be honest I am not sure, just something I found when googling
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  9. #9
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    Quote Originally Posted by linux-tech
    In short, you'll NEVER get dual NIC's to run redundantly. It's just not possible. You CAN assign the server base ip to one nic, and the other ip's to the other nic, but that's not the same, and it certainly isn't "redundancy".
    That's simply not true. Linux supports channel bonding which is analogous to NIC teaming from the Windoze side. You can bond as many NICs as tickles your fancy and get redundancy.

  10. #10
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    Quote Originally Posted by LowAsYou
    I have linux dedicated server and like to setup dual NIC cards for extra redundancy.. in case one NIC card fails.
    Are you sure you really need this? Does this box have dual power supplies with power cords being fed from different PDUs?

    If you're not fully committed to redundancy than having dual NICs is a largely wasted effort. From your post it looks like you are looking to run this back to a single switch, and that switch has a higher likelihood of failure than the NICs plugged into it.

    Port bundling increases the complexity of your implementation which makes things more difficult to troubleshoot. In this case you are looking at going from a single NIC that has an extremely low rate of failure to implementing a fancy software high availability solution. If the statistics from what we have seen in our environment with AIX/HACMP and other NIC teaming implementations are indicative of the technology in general, these solutions actually lower your availability. In the last 2 years since we've been supporting these implementations they have saved us from exactly 0 NIC failures but have caused several outages due to issues with the failover management process. In particular, we've seen secondary NICs takeover even when the primary had no connectivity loss (resulting in a brief outage during the switchover), or the NIC swapover process fail completely resulting in 0 NICs being active.

    While dual pathing is standard in the network world, it is done on systems where the vendor controls the hardware, the operating system software, and the device drivers that link the two. On the server side you are trying to make the same thing work with several different hardware combinations and multiple driver authors, and hoping they all agree on what the API specifications are. The probability of running into software bugs in that scenario is far higher than the likelihood of a NIC hardware failure.
    Eric Spaeth
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  11. #11
    short, you'll NEVER get dual NIC's to run redundantly. It's just not possible. You CAN assign the server base ip to one nic, and the other ip's to the other nic, but that's
    That is not so, check it. Simple HP Proliant 100TX cards have been able to do this since 1997


    http://h18004.www1.hp.com/products/s...g/teaming.html

    Buy 2 of these = problem solved
    http://cgi.ebay.com/Compaq-NC7770-Gi...QQcmdZViewItem
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  12. #12
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    I had this setup at calpop... When they did network maintenance... (or looking to move a server to another switch..) This setup helped so many times.. Now that i moved away from calpop.. i don't need it any more

    dollar nailed the link to RH thats the one i have in my bookmarks.
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  13. #13
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  14. #14
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    by RH i meant the Redhat link.

    Its easy to setup and managed, one thing i did love since its too uplinks you get more capacity, better in house transfers.
    Remote Hands and Your Local Tech for the Los Angeles area.

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