Re: LTM Bridge Versus Route Mode

Andy,

 

 

Take a look at the manual, http://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm_implementation/sol_vlans.html1062182. There are couple of diagrams there, which unfortunately comes across very fuzzy, at least to me. In bridge mode, there is flat network, say 10.0.0/24, using the manual as the example, and the servers being load balanced, LTM, and the default gateway for the network is al on the same subnet. The router for the network is 10.0.0.2 and the LTM is at 10.0.0.5. The servers are at 10.0.0.3 and 10.0.0.4. LTM is NOT going to be the gateway for the servers, the router is. They are in the same L2 broadcast domain.

 

 

Your scenarios 1 and 2 are both L3 routed mode. Once upon a time (v4 days), you did not have to have forwarding virtual server and SNAT would take care of outbound connections (or inbound as the case may be) to and from the servers across LTM.

hmm ok interesting. So in my scenario 1, this was back in 9.2 days and its been a while since doing that.... So are you saying that you have to use forwarding servers no regardless? Thanks for the url reference , I will go ver that as well.

 

 

 

Am I correct that node originated traffic (non-load balanced) would require a forwarding server to handle the outbound nat? I believe without this , for example if you assigned a snat pool at the vip level, the LB return traffic from server to client would work fine but server(LTM node) orginated traffic would not be nat'd outbound?

 

 

 

Yes, you will need a forwarding virtual server in a routed mode, in order for non-load balanced traffic to "route through" the LTM. For server to go outbound, you will need a forwarding VS with SNAT automap turned on, or NAT set up for that particular node.