Application Delivery (ADX)

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Contributor
Posts: 39
Registered: ‎05-04-2009

How do I allow my real server to contact a virtual server?

How do I allow my real server to contact a virtual server? The connection/request is not succesful all the time I am trying get send a request from one of my real server to a virtual server.

Setup:

client --- ADX --- real servers

There are two virtual servers at the ADX. One which is getting accessed by the client and another one for requests coming from the real servers itself.

Super Contributor
Posts: 316
Registered: ‎05-01-2009

Re: How do I allow my real server to contact a virtual server?

Hi,

is there by any chance a way for the real servers to communicate to each other bypassing the ADX? You might have a switch behind the ADX with all the real servers connected to this switch. A real server acting as client would send a request to the virtual server. The ADX is going to do the load balancing and it is going to replace the destination IP of the packets with the IP address of the real server choosen. The receiving real server is going to see a request from another real servers IP address to its own IP address.

This could result in the real server answering directly to the requesters IP address (IP address of the real server acting as client) and the return traffic is going to bypass the ADX. The ADX is not able to do the reverse IP translation in this case.

The requesting real server is talking to the virtual server but it is getting an answer from the real servers IP behind the virtual server. This does not work! The requesting real server expects the packet to come back from the virtual server IP.

Have a look at source-nat. You could enable source-nat quickly for a quick test. I hope this helps. Search for "source-nat" in the documentation to get some more details.

This is most probably for a multi-tier setup looking like:

client --- ADX --- real servers --- ADX --- real servers

with a single ADX instance in the network only acting as load balancer for all existing tiers.

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