ACE20 Rserver and VIP with the same IP

[spressle]

I have an ACE that I'm trying to get configured.  I need a rserver to have the same ip address and a class map vip address.  ex below.

rserver host RED

  description REDS

  ip address 172.95.94.250

  inservice

serverfarm host REDS

  transparent

  rserver RED 9000

lass-map match-all stb-RED

  2 match virtual-address 172.95.94.250 255.255.255.0 any

Shouldn't the transparent command under serverfarm allow this configuration?  When I issue the class map command I get this error message.

Error:  Entered VIP address is not the first address in the VIP range

software version

Software

  loader:    Version 12.2[121]

  system:    Version A2(3.6a) [build 3.0(0)A2(3.6a)]

  system image file: [LCP] disk0:c6ace-t1k9-mz.A2_3_6a.bin

  installed license: no feature license is installed

[Kanwaljeet Singh]

Hi,

You will have a IP conflict in network if you have two same IP's and that's why it is not allowing you to do the same.

You can configure the VIP and use this VIP as a secondary IP on the real server. That should take care of the requirement. But yes, ACE won't let you do what you are doing.

Regards,

Kanwal

[spressle]

But this same config is applied and working on another ACE.  I agree that it should not work but I have seen it working.  I thought the "transparent" command in the serverfarm config allows this to happen?

Thanks,

Scott

[Kanwaljeet Singh]

Hi Scott,

I tried in A5 train here in my lab and it didn't allow me to add the VIP if rserver is there with same IP and vice-versa. Do you know in which version you saw that it was allowing the same rserver IP and VIP?

Regards,

Kanwal

[spressle]

Hi Kanwal,

Thanks for trying this in your lab.  I believe it is A2 train.  I put a show ver in the first post so you could see the exact code I'm running.  What error message are you getting when you apply this configuration?  Thanks!!

Thanks,
Scott

[Kanwaljeet Singh]

Hi Scott,

This is what i get:

switch/Admin(config-cmap)# match virtual-address 1.1.1.2 tcp any

Error: VIP address is the same as an rserver IP in the context

Regards,

Kanwal

[spressle]

Hi Kanwal,

Do you have the "transparent" command in your serverfarm section?  I think that is what should allow this config to happen.  That is what someone else told me is that the command was the reason you can have both the rserver and the vip the same ip address.

Thanks,
Scott

[Kanwaljeet Singh]

Hi Scott,

Yes of course it is there.

serverfarm host tra

  transparent

  rserver tra1

    inservice

rserver host tra1

  ip address 1.1.1.2

  inservice

Regards,

Kanwal

[jsirstin]

Hi,

This is correct; you cannot have the VIP and real using the same IP in the config. This will be seen as a Dup IP from the ACE perspective since it owns the VIP IP. How you do this is to configure the server with a unique IP from the subnet configured on the ACE server vlan. This is what you use to define the real in the config. The server IP needs to be L2 adjacent to the ACE for this to work. The transparent keyword tells the ACE to just L2 forward the traffic to the Mac address the real resolves to, but keeps the vip IP as the destination. This is why the server needs to be L2 adjacent to the ACE so that it can see the REALs actual mac address.  Without the transparent keyword we NAT the VIP address to the REAL that gets the connections.

You will also need to create a loopback IP using the same address as the vip on the server.

The reason you need to use a loopback IP is so that the server does not arp for this address. You do not want the server to advertise that it owns this address since it is already assigned to the ACE VIP.

The link below is for IOS server load balancing but the loopback samples are still relevant.

http://www.cisco.com/c/en/us/support/docs/routers/7200-series-routers/10567-37.html#topic1

I hope this information is helpful

Best regards

Jim