HSRP vs GLBP

[ciscosupport99]

Regarding GLBP - after using both HSRP & GLBP I wonder one one might choose HSRP over GLBP ?

Would you comment please ?

[tcordier]

HSRP is preferable when you use the second link solely as backup link. A standard situation would be an ISDN dial-up backup link, when you want the backup only to be used when the primary fails. If you use GLBP in such a configuration, ISDN will be up continously, and generate costs. Other instances where HSRP is preferable would be when your backup link has less bandwidth or higher latency. GLBP is unaware of possible performance issues with the backup link, and you can not control which traffic will be sent over the backup.

- Thomas

[ciscosupport99]

Understood - thanks Thomas

[ropethic]

GLBP is a true load balancing protocol. With HSRP in order to load balance across two routers you need to create two HSRP groups. GLBP provides load balancing wihtout the need to configure separate primary / standby groups.

GLBP selects an AVG (active virtual GW) and load balances using round-robin, weigthed or host dependent.

If there is no need for load balancing across gateways then HSRP is fine. Also GLBP requires minimal IOS requirements, that some organizations do not have deployed. So HSRP is supported in lower IOS revisons. Some orgs do not need or want to upgrade IOS.

[Joseph W. Doherty]

Robert's mention of load balancing across two routers using two HSRP groups, or MHSRP, can be an example of an instance where you'll want to use HSRP rather than GLBP. GLBP splits traffic, I believe, by source MAC. So if lots of traffic is being souced by one or only one device, using a single MAC, all its traffic will all take the same gateway. If you can point the source at two routers each with their own HSRP addresses (with standby on the other), you may better load balance the traffic to the gateway routers.

[ciscosupport99]

Interesting perspectives - thanks gentlemen.