LTM Clarifications
I'm working on the design to implement two 4200V's into our datacenter with a minimum amount of changes to either the nodes or the network.
From the research I've done, we are looking at using a hybrid of "Routed Mode" and "One-Arm" (correct me if i'm wrong). At this point, I've decided to place these connected to our Core Switches in a port channel across both 10Gb interfaces, with all required VLAN's trunked. We do have the luxury of being able to dedicate a new subnet to move certain nodes logically behind the LTM's using the LTM as a default gateway. However, we also have some nodes on a "flat" VLAN which we cannot move, primarily, Exchange CAS.
A couple of questions, I'm not 100% clear on these (forgive my ignorance).
- If we were to make the LTM the default gateway for the nodes, do we still need to SNAT? Since traffic will be forced to traverse the LTM to get to any clients, is it necessary?
- In "routed" mode, are the client IP's preserved? We don't want to expose ourselves as an open SMTP relay, so we have SMTP secured to specific client IP's on our CAS servers. If we do not SNAT, will the CAS see the client IP as the LTM?
- What is the best way to provide SMTP load balancing in a flat network? We have an old NLB address configured for many devices/servers to send to that would be difficult to update across the organization. How can we preserve the client IP with a virtual server on the same VLAN?
- Are the Management and TMOS routing tables seperate? For example, the management interface is on a subnet with other hosts that send email to a Load Balance SMTP gateway, will the return traffic route through the management interface?
Any help appreciated.