best practice and setup for HSRP

Unanswered Question
Apr 17th, 2009

Hi all, We are having some dist switches installed for the access layer, we paln to put in HSRP, my question is, should I leave the default timers of 2 and 10, or shoudl i make them less? OR should I use GLBP ?

Also, I want to have all the clients on one side, would I use standby group 1 for all VLANS ?, so on each vlan, i issue the standby 1 command ?

cheers

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davy.timmermans Fri, 04/17/2009 - 05:43

GLBP vs HSRP depends on the design:

If you have a looped layer 2 design:

=> HSRP

If you have a loopfree layer 2 design:

GLBP (if the uplinks to the core are equal)

A looped layer 2 design is a design where you've a complete L2 triangle ( access switch with a L2 uplink to each distribution switch + a L2 link between the distribution switch. This means that

If in this situation distribution switch 1 is root bridge for vlan x, the uplink towards distribution switch 2 will be blocked. All traffic for vlan x will go via distribution switch 1.

==> this means that your hsrp active router must be on the same switch as your root bridge. Otherwise you'll add an extra hop in order to reach the active router. ==> image that DS 1 is root and DS2 is active HSRP. This means that traffic will go via DS1 (because not blocked by STP) and then go over the crosslink between DS1 and DS2 in order to reach the active router.

In a loop free design you've a L3 link between DS1 and DS2. This means that no uplink is blocked by STP.

For the timers it's recommended to finetune them to subseconds

for example:

standby 1 timers msec 200 msec 1000

You can use an HSRP group/vlan in the access layer.

As I said before, the choice between HSRP/GLBP depends on your design

carl_townshend Fri, 04/17/2009 - 07:01

ok, thankyou

so, do I do

int vlan 1

standby 1 ip x.x.x.x

int vlan 2

standby 1 ip x.x.x.x

Am I ok using the same group, I dont wish to load balance so im sure this will be ok ?

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