Question : Cisco Content Switching

I  am trying to gather general information on how to plan/deploy web server load balancing using Cisco Content Switches and/or the Content Services Module for the Catalyst 6500.  We don't own this hardware yet but I want to limit the answers to those relevant to this particular situation, so "don't use Cisco, use F5!"-type answers won't be very helpful in this case.

With the standalone content switches, it appears that they are designed to have the web servers plugged directly into them.  I saw some mention of deploying them in a "one-armed" configuration with a VLAN trunk, but can this be done without having the web servers on their own VLAN from the rest of the network?

Similarly, with the CSM in a 6500, does this then require you to have the web servers  plugged into that particular 6500 for it to be able to load balance between them?  It would be nice to be able to deploy the load balancing somewhat centrally and not have to worry about the physical proximity of the web servers, nor re-addressing the servers themselves.

Finally, any pointers to good specific documentation on these kinds of issues would be most appreciated.

Answer : Cisco Content Switching

> With the standalone content switches, it appears that they are designed to have the web servers plugged directly into them.

Web servers do not have to be plugged directly into the content switch. There are two nasic modes for content switches, bridge mode and a layer 3 mode. I am most familiar with bridge mode. A thorough understanding of spanningtree is helpful. Essentially, you use the content switch to bridge two vlans, thus switching all traffic to the servers. A typical deployment would be like this:


FW -- (VLAN A) ----Content switch ---(VLAN B) ---- Access Switch ---- Servers

The key here is to allow BPDUs to pass through the content switch thus allowing VLANs A and B to merge creating one root bridge. The content switch would be configured as the root bridge in this scenario. In this design all traffic will flow through the content switch to the servers through the content switch which allows the device to enforce load balancing rules. More info:

http://www.cisco.com/en/US/products/hw/contnetw/ps792/products_configuration_guide_chapter09186a008028ff8c.html

> I saw some mention of deploying them in a "one-armed" configuration with a VLAN trunk, but can this be done without having the web servers on their own VLAN from the rest of the network?

Yes, the servers are on the same vlan as the content switch, with a firewall (for example) as a gateway. There is also a VIP configured for load balancing, all traffic destined for the VIP will get routed to the content switch and thus load balanced. However, this does degrade the perfromance of the content switch (Cisco). Here is the DOC:

http://www.cisco.com/en/US/products/hw/contnetw/ps789/products_configuration_example09186a0080093dff.shtml

> Similarly, with the CSM in a 6500, does this then require you to have the web servers  plugged into that particular 6500 for it to be able to load balance between them?

No, you can balance the traffic at one layer and attach the servers to the next, however, the layer two infrastructure needs have logical connectivity.

> Finally, any pointers to good specific documentation on these kinds of issues would be most appreciated

http://www.cisco.com/en/US/products/hw/contnetw/

harbor235