can i achieve loadbalancing for single subnet in Lan using HSRP

Answered Question

Can i achieve loadbalancing for single subnet (192.168.1.0/24) in LAN using HSRP? I don't want to split the subnet.

Thanks in advance..

I have this problem too.
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Correct Answer by Richard Burts about 8 years 7 months ago

Bhupesh

Yes you can have more than 1 HSRP group in a subnet. There is not a need for different subnets and not a need to break up the subnet.

HTH

Rick

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Richard Burts Tue, 04/15/2008 - 08:06

Bhupesh

There may be an alternative that would work for you using HSRP. Configure 2 HSRP groups on that LAN. Assign priorities so that one layer 3 device is the active router in one group and that the other layer 3 device is the active router in the other group. Then assign half of the clients in the LAN to use the first HSRP address as their default gateway and configure the other clients to use the other HSRP address as their default gateway. The configuration might look something like this:

interface fastethernet0/0

ip address 192.168.1.1 255.255.255.0

standby 1 ip 192.168.1.3

standby 1 priority 105

standby 2 ip 192.168.1.4

standby 2 priority 101

If you do this then half the traffic should go through one router and the rest of the traffic should go through the other router.

HTH

Rick

Correct Answer
Richard Burts Tue, 04/15/2008 - 11:24

Bhupesh

Yes you can have more than 1 HSRP group in a subnet. There is not a need for different subnets and not a need to break up the subnet.

HTH

Rick

Joseph W. Doherty Tue, 04/15/2008 - 16:37

Additional notes:

The feature of HSRP that Richard is describing is known as MHSRP. It used to limited to higher end routers but I believe most of the later routers support this feature. For additional information on this feature see the section "Configuring Multiple Hot Standby Groups" within: http://www.cisco.com/en/US/docs/internetworking/design/guide/nd2022.html

PS:

Another feature of MHSRP, when not being used for load balancing gateway clients, is the active gateway can send redirects using other gateway's virtual IP. (Normally HSRP won't redirect because is would pin clients to a physical MAC.) I believe GLBP supports this feature too.

Jon Marshall Tue, 04/15/2008 - 11:29

Bhupesh

Rick is correct in that you can do this with HSRP. However if you are looking for load-balancing that is exactly what GLBP is designed for and it does the job more effectively.

So you have a vlan with 50 clients in. With HSRP 25 are assigned to one router and 25 to the other. 20 people in the first 25 are using the network bit only 5 from the second 25. Result is you are not really load-balancing equally.

GLBP does not work this way. You have one virtual IP on the clients, the same on all clients and the active router decides which router will handle eahc individual request.

There is nothing wrong in the HSRP approach but as your question asked about load-balancing then GLBP would be the protocol to use.

Jon

dbroder Wed, 04/16/2008 - 10:11

I'm with Jon on this one. One thing to note about the HSRP suggestion is that you will have to deal with different DHCP scopes/details -- you'll have to figure out a way to assign different router IPs to your hosts based on which router you want them to use.

Essentially, you'll have to have two scopes defined for the same subnet... an ugly situation to manage going forward.

Darren.

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