HSRP fast failover.. how fast? 1

[molecul3]

Hi all,

I was just reading up on HSRP and it is stated that it supports fast failover. but is it fast enough to be transparent or does connectivity drop for a second or two? And does it also depend on how the network is set up. Can anyone also tell me .. (based on experience), what is the best way to set up HSRP for a group of 2 routers. i.e. what should be in the configuration and other elements (if applicable) that will affect failover if not configured or not configured correctly. Any help is much appreciated.

 

[ADB100]

You can achieve sub-second HSRP failover by reducing the hello timers to sub-second (HSRP will failover if 3 hellos are missed). You obviously need the rest of the network (or the bit you are in if OSPF stub areas etc) to converge as quick or quicker than HSRP. If you design the network right and have equal-cost paths then it can easily be achieved.

Users will not notice the failover, you may miss a couple of packets, but in something like a VoIP scenario you are likely to hear a very minor break in the speach.

HTH

Andy

 

[molecul3]

Thanks ADB100.

That made sense. I guess you can't really tell till you actuall test it out. but the problem is always not having the opportunity to test things like that in a live environment where uptime is a must. anyways, i am still a beginner and looking at learning so if you could point me in the right direction, i am sure resources are aplenty. thanks again.

 

[ADB100]

Best resource is CCO. HSRP details here:

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a008042fbb3.html

You are looking at the 'standby msec' commands. For routing protocol convergence timers have a read of the relevant routing protocol sections - OSPF here:

http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a00804556cc.html

Basically just have a search, there are also some good SRND's available on CCO (

http://www.cisco.com/go/srnd)

HTH

Andy

 

[molecul3]

ahhh.. that SRND site looks like it has heaps of info. will go through them one by one. Thanks a lot Andy. Much appreciated.