802.3ad and active-backup on RHEL4

  • We have a few servers where we have 4 nics, two going to each switch, and we want to configure 802.3ad on the nics going to each switch, and then do active-backup over the two switches. Something like this (hoping my ascii-art survives):

                     eth0   -----\ active -------<802.3ad        Switch1
                     eth1   -----/

                     eth2   -----\ backup -------<802.3ad        Switch2
                     eth3   -----/

    Does anybody know if this is possible with bonding on RHEL4 ?

    • littone

      Hmm, haven't tried myself, but it is probably possibile if you create two bonds,
      first one with eth0 and eth1 as slaves, and second bone with eth2 and eth3 as slaves?

    • Jay Vosburgh
      Jay Vosburgh

      You (probably) don't need to run active-backup over the two separate bonds.

      When connected to two separate switches, 802.3ad will create two separate aggregators (one for each switch) and select one of them as the initially active aggregator.  If the active aggregator should fail (all links go down), then 802.3ad will automatically reselect a new aggregator, which will switch traffic to the other switch.

      This won't permit switchover to a backup aggregator prior to all links failing in the active aggregator (but you'd have the same problem running active-backup over 802.3ad).  The only real deficiency as compared to active-backup is that you can't specify a "primary" option to prefer one set of slaves.