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what do you do to avoid downtime caused by top-of-the-rack switch hang / malfunction? some possible solutions are can be found in this presentation.

i'm interested in hearing how do you approach the problem when automatic fail-over is necessary.

edit some possible options:

  • spanning tree run at each server as suggested by womble
  • ethernet bonding in active-backup mode as described here.
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3 Answers 3

For things that need that level of protection (risk/reward calculation justifies the extra expense, given the low probability of occurance -- unless you're buying really shoddy switches they just don't fail very often) I just dual-path everything -- two switches, one hooked to an on-board NIC the other to an off-board NIC (preferably different models/manufacturers, to protect from driver/NIC failure), then the edge switches hook to a pair of distribution or core switches (as appropriate), which then hook up to a pair of core routers, and so on. Everything's duplicated.

Bonding is configured to test links via ARP and cutover to the other switch in the pair if, say, a core switch dies (although everything is cross-connected too). Let spanning tree deal with the redundancy, which in my experience is a lot more robust than the author of those slides suggests.

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thanks; do you use LACP or other protocol? what do you mean by 'dual core' switches - single fully redundant device or stacked up multiple chain of them? –  pQd Nov 22 '09 at 11:58
    
LACP doesn't work across multiple independent switches. We use separate devices everywhere; stacked switches have a much higher risk of simultaneous failures in my experience. –  womble Nov 22 '09 at 12:24
    
ok - so is every machine spanning-tree aware? –  pQd Nov 22 '09 at 13:03
    
Yes, of course. –  womble Nov 22 '09 at 14:04
    
do you set up bridge over vlans under linux? if so - do you mind posting snippet of your config or pointing some example? thanks. –  pQd Nov 22 '09 at 18:12
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i'll answer myself in this case since idea of running STP at the client presented by womble slightly freaks me out. it seems that:

  • bonding between the server and two independent switches with periodic connectivity checks [ arp_ip_target parameter ]
  • RSTP in the core / between switches

is most reasonable solution.

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pQd, what bonding mode are you using as a result? active-backup, balance-alb or other? –  cronfy Oct 31 '13 at 15:31
    
active-backup; i don't need more bandwidth - just resiliency. –  pQd Oct 31 '13 at 15:41
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We simply don't use 'top of the rack' switches. We either use blades with in-built switches that are trunked back to redundant distribution or core switches or we patch servers straight through to redundant distribution switches (ideally running VSS).

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