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We have an inline network product that has a failsafe mode using bypass network cards (ie network cards that will physically bridge two interfaces if power is lost or some other problem develops).

Between two hosts, the timeout is usually only about a second. When a switch is involved it seems to take upwards of 30 seconds to a minute. Is this just the time it takes switches to establish link? Does anyone have any experience with this?

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up vote 3 down vote accepted

That 30-50 second delay is the result of Spanning-Tree Protocol. If you're connecting two switches, it's recommended you leave it alone. Otherwise, you can essentially disable STP for that port by using the "portfast" feature. If it's a Cisco switch, this is accomplished by performing the following after logging in and entering "enable" mode:

switch#configure terminal
switch(config)#interface fastethernet 0/1
switch(config-if)#spanning-tree portfast

Be sure to 'write mem' when you're done.

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+1 The basic idea here is to disable and hard-code anything that needs negotiating between he switch and host. Hard-coding link speed/duplex may gain you a small improvement as well. –  Zoredache Oct 26 '09 at 19:15
    
If that link is a trunk to his security device he may wish to use trunkfast instead of portfast. Both are better than flat out disabling STP on the interface like I've seen many do. –  sparks Oct 26 '09 at 19:16
    
You think it's solely this? The little switch in my basement does STP, but it doesn't take 30 seconds for link to come up. –  user24048 Oct 26 '09 at 19:40
    
What is the model of the switch in your basement? Most of them don't do STP, heck some of the HP switches for blade chassis don't do STP. –  sparks Oct 26 '09 at 20:11
    
+1. It sure sounds like STP to me. The port in question will spend about 15 seconds in the litening state and about another 15 seconds in the learning state before it goes into the forwarding state. Enabling portfast should allow the port to go immediately into the forwarding state. –  joeqwerty Oct 26 '09 at 23:30
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