KEMP Technologies released the 5.0 LoadMaster firmware for LoadMaster 2000 and above models on Tuesday. It brings VLAN trunking (802.1Q) as well as Etherchannel to the LoadMaster series.
Not as prominent in the press release, but I personally think is the neatest feature, is the dynamic transparency. Transparency is when the source IP address of the client is maintained, which is the default method for most load balancer. The LoadMaster’s non-transparency is probably known more commonly in the industry as Source NAT, or SNAT. This is when the client’s IP address is replaced by an IP on the load balancer.
When preserving the true source IP address of your clients, you cannot have clients on the same network as your servers. This is sometimes referred to as “the same subnet problem”. The cause of this is that the traffic needs to pass through the load balancer on the way out. If the client is on the same subnet as the servers, the servers reply directly to the client, rather through the load balancer.
The solution for the same subnet problem is usually to enable SNAT/non-transparency, but you lose the true source IP address of your clients, so the web server logs will show everyone coming from one address.
The higher-end load balancers have the ability to do selective SNAT, and now KEMP has the ability to do selective SNAT automatically. I’ve yet to see it in action, so I can’t attest to how well it works, but it’s potentially a very nice feature.
