Cisco Load Balancer

As per previous posts Load balancing can either be hardware or software based. In the Cisco world software based load balancing is handled by IOS SLB! That’s a bit of a mouthful, so lets list out a few definitions to make it clear:

IOS stands for Internetwork Operating System and consists of a combination of switching, internetworking and telecommunications functions all of which are integrated within a multitasking operating system, and

SLB stands for Server Load Balancing and is used to balance load (packets) across multiple servers

Ok, so IOS SLB is supported by the Cisco Catalyst 6500 switch which in my experience is the core network switche in operational use today by large corporations. The following video provides an overview of this switch:

For hardware load balancing the Application Control Engine (ACE) service module for the 6500 is required. I can’t find a handy video on the ACE module but here is one for the ACE standalone appliance which gives an overview of the capabilities of ACE:

The basic idea behind SLB is to balance the load across multiple servers. In some cases the sessions on the servers need to be sticky (shopping cart as an example) and in some cases this is not needed, the Catalyst 6500 supports sticky sessions so either approach is supported.

As in previous posts there are many advantages to SLB:

• scalability
• performance
• high availability
• resilience
• redundancy and so forth.

Hope this is useful. If you see any better videos let me know!