using two switches without 802.3ad support I can configure bonding mode 4? ie:

server linux with 2nics: put nic1 cable on switch1, nic2 cable on switch2 and put another cable from switch1 to pc1 and another cable from switch2 to pc1? Obviously with bonding active on both pc.


No. Mode 4 is for 802.3ad -- this protocol allows your server to talk to the switch and establish a bonded interface on both sides of the link. If your switches don't support it (or you're using switches that aren't stacked so they can form a single channel group that crosses both switches), then your channel group won't form correctly.

You probably want mode 6, which offers better load-balancing and doesn't require special switch support. In any event, don't implement bonding in a production environment without testing both failover and throughput to be sure you are getting what you think you should. In particular I've seen cases where performance of specific switches degrades instead of improving.

Also in many cases involving just two end-points you won't get more than the bandwidth of one link in the aggregate in the receive direction. This means if you have, for example, box1 with a bond composed of 4 x 1gbps links and box2 with a 10 gbps link (not bonded, just 10g), then box1 will be able to transmit to box2 at 4gbps, but will only be able to receive data from box2 at 1gbps. Bonding really only shines in cases where you need more bandwidth asymetrically between two endpoints, or where you have many endpoints communicating. (Of course if all you need is failover, it's great.)

Check out any of the numerous google hits (like this one) for more explanation of bonding.

I hope this helps.

  • In addition to this answer, if you just want transmit load balancing based on hash of traffic, you can use Mode 2 bonding. You still need an EtherChannel or similar config on the switch. If you can't configure your switch, you could try Mode 5 or Mode 6 but they cannot be used when the bond is in a bridge with virtual machines. – suprjami Nov 17 '14 at 22:04

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