11-09-2007 07:00 AM
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
11-09-2007 10:43 AM
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
11-09-2007 10:51 AM
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
Thanks guys...
Anthony
11-09-2007 11:25 AM
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
11-13-2007 05:05 AM
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
11-13-2007 11:17 AM
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.
11-14-2007 03:17 AM
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.
11-16-2007 10:57 AM
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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