Unanswered Question
Mar 28th, 2008
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As I underatand it, the only qualitative difference between HSRP and GLBP is that GLBP offers load balancing by allowing all routers in a GLBP group to forward traffic, unlike HSRP, where you have an active router and the other is in standy.

So, I saw some client configs on a few of their routers, where they have GLBP configured instead of HSRP, but then they have load balancing shut off with the "no glbpp load balancing" command.

Im thinking to myself "why would they do that"? Why not just use HSRP and be done with it? Without GLBP's load balanacing feature, what qualititative difference is there?

Any ideas?

Thank you

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Joseph W. Doherty Sat, 03/29/2008 - 05:05
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There's HSRP V1 and HSRP V2; the latter sharing some new features with GLBP, but the former (usually) the default. Perhaps, if they didn't know about V2 HSRP, that could be one reason GLBP was chosen. Or, they wanted the option to enable/disable load balancing, but at the moment they decided disable it. Or, they rushed into using GLBP and encountered some asymmetric path issues but decided not to move back to HSRP. (For instance, I've seen brand X switches get a bit confused, from their management IP, when they see the same virtual MAC on two ports.)

cisco24x7 Sat, 03/29/2008 - 09:31
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If your network looks something like this,

GLBP will NOT help at all.

CCIE Security

dbroder Sun, 03/30/2008 - 19:05
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GLBP's ability to use 'group' numbers above 256 (to 4096 I believe) allows you to co-ordinate your VLAN and GLBP numbers for to self-document your code.

A small item to be sure, but definitely a plus.


MW20082008 Mon, 03/31/2008 - 07:34
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Thanks, guys.

I was wondering if there was some real qualititative difference in terms of operation that would make somebody do something as counter intuitive as configuring GLBP when doing IOS-based SLB, which is a no no.



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