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New Member

CSM Load Balancer Help

Hey,

Just a quick question....

Does anyone know a) if it's possible and b) how to have two servers off the CSM but instead of load-balancing between them make them a failover pair i.e. if server A goes down server B will take over - done using the same VIP?? It's needed because the application on the servers can't do load-balancing yet but can work in a failover way.

I'm reading the book trying to work it out but if someone has done this before that would be great!

Thanks

Anthony

7 REPLIES

Re: CSM Load Balancer Help

You can do it by creating two serverfarms one as primary and one as backup. Under Vserver call them as needed.

eg

serverfarm App1-Primary

nat server

no nat client

real 10.10.10.1

inservice

serverfarm App1-Secondary

nat server

no nat client

real 10.10.10.2

inservice

vserver APP1-vserver

virtual 172.16.200.60 any

serverfarm App1-Primary backup App1-Secondary

inservice

A If you want CSM to show the Vserver as operational even if it is serving backup serverfarm then you can configure a CSM variable:

#var AGGREGATE_BACKUP_SF_STATE_TO_VS 1

Hope it helps

Syed Iftekhar Ahmed

New Member

Re: CSM Load Balancer Help

Thanks for the responses.

I'm using CSM 4.6(6) and have given what you suggested a go but have run into problems.

When I disconnect the primary server I see that go out of service but that also knocks out the VIP and it never fails over to the second server. Am I missing something? I've attached the relevant parts of the config and would be greatful for any advice.

serverfarm FARM1

nat server

nat client WEB

real 10.2.250.10

inservice

probe HTTP

!

serverfarm FARM2

nat server

nat client WEB

real 10.2.250.11

inservice

probe HTTP

vserver WEBTRAFFIC

virtual 10.2.250.100 tcp www

vlan 250

serverfarm FARM1 backup FARM2

persistent rebalance

inservice

I also had a go at creating that variable but it wouldn't let me...just said variable not configurable - but I'll play with that and see if I can work it out...I'm not so bothered as long as the backup part works.

Thanks guys...

Anthony

Re: CSM Load Balancer Help

Anthony~

I dont have a CSM at my disposal but the config I suggested should work.

You dont need to create that variable. It should be there with value 0.

Following command will show you that

sh mod csm x var | incl AGGREGATE_BACKUP

where x is the slot where CSM is installed.

You should be able to change it using following commands

Cat6500#conf t

Cat6500(config)#mod csm x

Cat6500(config-module-csm)#var AGGREGATE_BACKUP_SF_STATE_TO_VS 1

Thanks

Syed Iftekhar Ahmed

New Member

Re: CSM Load Balancer Help

That's great guys, thanks for the help. The failover part is working nicely now.

I have one other question that I think you may be able to help me with however....

At present the source IP (when it arrives at the load-balanced servers) is the VIP of the load balancer. If I take out the NAT command from the serverfarm nothing works.

So is there a way to get the real source IP through?

My config for this is:

natpool WEB 10.2.250.100 10.2.250.100 netmask 255.255.255.0

serverfarm FARM1

nat server

nat client WEB

real 10.2.250.10

inservice

probe HTTP

Thanks again for the help.

Anthony

Cisco Employee

Re: CSM Load Balancer Help

Anthony,

if it fails when you remove client nat this is because your server is not responding to the CSM but to the client directly.

You can force the server to respond to the csm by setting up correctly the server routing table.

Make the CSM the default gateway or insert a static route for the client.

It's just a routing issue.

Gilles.

New Member

Re: CSM Load Balancer Help

Hey Gilles,

I understand. The problem I face is that I also have a FWSM in the equation and have that as the server's DG. I can't have the servers bypassing the firewall so what would you recommend - some PBR somewhere?

My flow idealls needs to be something like this:

1. Client hits VIP of load balancer

2. LB routes that to server farm via FWSM

3. Server replies via FWSM

4. Client sees content

Thanks.

Cisco Employee

Re: CSM Load Balancer Help

if you configure the CSM in bridge mode - bridge the server vlan and the FWSM vlan, then you can keep the FWSM as the default gateway for the server and traffic will go accross the csm anyway so that client nat can be disabled.

Gilles.

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