High Availlibity using HSRP and GLBP

Unanswered Question
Oct 28th, 2008

Hi, We need to upgrade existing flat network having 3750*4 and 2950*7 switches without Vlan's to proposed network with High Availibility using 45XX suitable switch bwteen these 3750 and 2950, because we are offering emergency services.

Kindly help in configuration and supported 45XX series swith for this network.

Thanks in Advance

I have this problem too.
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satish_zanjurne Wed, 10/29/2008 - 00:44


instead of using Catalyst 4500, use catalyst 6500 it would be good for your future requirements also.

It would be good if you design using Hierarchical architecture like Core, Distribution,Access layers.

Configure HSRP on Core devices like Catalyst 6500 , do the load balancing, like create multiple HSRP groups.

For few vlan make one 6500 as Active & other as standby, for other vlan's make other 6500 as active & first one as standby.

Below mentioned link will be useful for HSRP




GLBP configuration on 6500


HTH...rate if helpful..

Amit Singh Wed, 10/29/2008 - 06:22

You can configure both HSRP and GLBP on the Cat4500 as well. GLBP is supported on Cat4500 as of 12.2.46 IOS release, so you might have to upgrade the IP base image on the supengine.

As per the present devices you can very much fulfill your requiremnt with Cat4500 and configure the desired topology.

bishnbaajee Thu, 10/30/2008 - 07:50

thank you .. I'm not sure whether can we maintain both the 4500 or 3750 switches into active/active mode using HSRP or GLBP..

anything on this please provide the solution..


John Blakley Thu, 10/30/2008 - 08:04

There's no such thing as active/active with these protocols (that's a PIX/ASA reference). GLBP is used for load-balancing, and would be your best bet to use if you are wanting to provide multiple paths for traffic. HSRP is strictly failover, and will only be in an active/standby state.


bishnbaajee Thu, 10/30/2008 - 08:27

could you please clarify,whether it possible to use active/active mode HSRP by configuring two different ip networks and one is active for IP set and other is Standy..vice versa..?

John Blakley Thu, 10/30/2008 - 08:30

Well, yes but that's more considered load balancing. You would configure 2 groups with 2 different virtual IPs, but it's still not active/active, just active/standby - standby/active.

You would set different priorities on each group and set preemption on the other.

Rate if helpful....


bishnbaajee Thu, 10/30/2008 - 08:44

thanks.. now I got the clarification of both.

i'll try for both etherchannel and GLBP configurations..

Joseph W. Doherty Thu, 10/30/2008 - 16:18

Unclear how a 45xx will improve HA when configured between existing 3750s and 2950s. 3750s provide fairly decent HA when stacked. 2950s should support STP.

Could you clarify why your existing devices don't provide the HA you desire and how a 45xx will (again, especially if you retain existing devices).

Also, unclear how you see HSRP or GLBP helping you since you haven't really described any L3.

pkaretnikov Thu, 10/30/2008 - 20:02

The biggest flaw with he 1U switches is the possibility of power supply failure and that they use external cabling. The 4500s are a definite step up in maintaining L2 or L3 availability.

Also the 4500s can do exactly one thing that 6500s still can't do... upgrade your IOS without downtime. I love 6500s but for most situations a 4500 has a slight advantage.

Since we don't have any specifics on network requirements we can only assume that a 4500 has the power and backplane to handle what you are planning since it works for most situations.

bishnbaajee Thu, 10/30/2008 - 22:19

Presently we have only two 3750's and, if we configure HSRP one is in standy..instead of going for another two 3750's, advisable to use 4507 and for feature expansion also..

kindly let me know another solution

Joseph W. Doherty Fri, 10/31/2008 - 03:29

Two 3750s, but your original post has "3750*4"?

The two existing 3750s are not stacked? I'm curious, why not?

Unable to comment too much on feature comparison, but the 4500 series doesn't seem all that much better in features than the 3750 series. I'm also curious, do you have some particular features in mind?

Joseph W. Doherty Fri, 10/31/2008 - 03:50

"The biggest flaw with he 1U switches is the possibility of power supply failure . . ."

Not totally true if you use RPSs, but certainly not as tidy as dual power supplies in a chassis.

. . . and that they use external cabling.

True, but they also usually use less space than a chassis and you have a few additional deployment options, such as not using a rack or placing them across multiple racks, e.g. top-of-rack.

"The 4500s are a definite step up in maintaining L2 or L3 availability."

I'm not totally convinced they are a major enhancement although I'm sure they offer some enhancement. They are a definite step up in CAPEX and OPEX.


Something to keep in mind with any chassis solution, per port cost is high with few ports (cards) relative to stackables. However, you load them up, and per port cost can be less than stackables (at least CAPEX).


Don't know how important this might be to you, but the non-E 4500 is a bit light weight bandwidth capacity for supporting lots of gig.

bishnbaajee Fri, 10/31/2008 - 04:49

Thank you for your concern, presently we are using only two 3750's into emergency services which are dedicated, and near feature we are planning to setup this site into DR site for 8 branch sites.. data replication and centralized network. Keeping in view i am planning modular based swith with High Availability..



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