What is possible with direct server return and what is not?

[Anonymous]

Is there some kind of general rule? I had a look at some posts and it looks like DSR is restricted in some areas due to protocol limitations (it is technically just not possible to do DSR together with some stuff).

[Anonymous]

You are right - it is sometimes just not possible to use DSR because protocols like IP/TCP and so on do not support what would happen in these cases. DSR is working as long as it is only the DMAC of a packet which is getting changed. This is what DSR is getting used for. The return traffic does not need to pass through the load balancer using DSR. Everything which needs to change the traffic at L3, L4 or at L7 does not work together with DSR. On top of that: everything which needs to see the answers of the real servers for some reasons does not work with DSR.

The following things are therefore NOT possible:

- Adresse translations

- SSL offload

- Layer 7 Switching

- Port mapping

- Compression

and so on

[Anonymous]

I guess I know the answer but what is with TCP-offload and DSR? I guess the answer is that this is not working but I would like to be sure.

[Anonymous]

TCP-offload requires that the replies do come back to the ServerIron because the ServerIron is going to handle the backend sessions. It is therefore not possible to use tcp-offload together with DSR.