about Direct Server Return

[michael_wang_ironport]

Dear all:
Who did configure ironport appliance DSR function? I want to know when I enable DSR/VIP so that can implement loadbalance about ironport appliance, I must need layer 4 switch, really?
I can't find this requirement in ironport advance user guide, ironport advance user guide is very simple about this function description. Who have detail configuration document about ironport appliance DSR function? If you are convenience, please email to me(wangjingpu@msn.com), I will say "Thank you very much much much".
:D

[Donald Nash]

I just implemented DSR earlier this week. Yes, you need a layer 4 switch to make it work. We use Citrix NetScalers. I don't know if other layer 4 switches can do DSR, but that's only because I haven't used them. I'd be surprised if NetScalers were the only layer 4 switch that could do DSR.

As for what you do on the IronPort side, I simply followed the instructions in the "Direct Server Return" section of the "Advanced Network Configuration" chapter of the Advanced User Guide.

[michael_wang_ironport]

HI dlnash:
Thank you for your reply! I will check this function configuration. But I think if DSR function need layer 4 switch, why ironport company develop this function, becuase we can complete Round Robin for two ironport appliances only by layer 4 switch when we need load balance or HA, we needn't DSR. :)
I will discuss this function with ironport CSE engineer.:(

michael

[Donald Nash]

But I think if DSR function need layer 4 switch, why ironport company develop this function

Because it works together with the layer 4 switch. You do not need DSR, but DSR lets you use a lighter weight form of load balancing. With DSR, return traffic from the IronPorts to the SMTP client does not need to pass through the layer 4 switch. If you design the entire system from the beginning to use a layer 4 switch then this is not so important. But if you add a layer 4 switch later, it is very helpful.

[michael_wang_ironport]

HI dlnash:
Thank you for your explain. if I have another questions, we could be discuss each other. :D

michael