router interface switching modes

[rj.remien]

I would like to know what the best type of switching mode is for router interfaces. I have site to site VPNs across the WAN. Should I use "no ip route-cache" interface command? What other options are there? Does it matter if you are running VPNs vs Frame relay? Is there an article someone can show me?

Thanks,

RJ

[donewald]

RJ,

Your switching options are the following (depending on IOS).

process switching

fast switching

autonomous switching

silicon switching

optimum switching

flow switching

no ip route-cache is process switching and unless you are doing something that would require this I would not do this.

Default is fast switching which is less process intensive than process switching.

CEF is the way you want to go if you can (globally "ip cef") will enable CEF on all capable interfaces. Should work with your VPN.

Here's a link on CEF http://www.cisco.com/en/US/partner/tech/tk827/tk831/tk102/tech_protocol_home.html

Hope this helps you,

Don

[rj.remien]

Thanks Don,

This is what I was wanting. I do have two more questions.

I read that fast switching is not desirable on low speed interfaces when data is fed from a higher speed interface.

I have VPNs that have FastEthernet interfaces for LAN input and Ethernet interfaces for output on 1721's. I also have a 2600 that has an Ethernet for LAN input and 128 Kb (ISDN) for output. One other setup is 2600's with Ethernet interfaces for LAN input and T1 interfaces (1.5 Mb) for output.

1. Should I enable CEF for all interfaces except the ISDN interface since it is much slower?

2. I have a hub and spoke topology. Should I use the command "ip route-cache same-interface" on the hub interfaces for maximum performance? Or will this be a performance hit?

Thanks,

RJ

[gfullage · Accepted solution]

1. Enable it on all interfaces, the router will handle the buffering if it can't transmit the data fast enough, it'll still be less load on the router CPU.

2. Yep, definately do that.

[rj.remien]

Thanks for your input.

I did the following:

ip cef global config on all routers

ip route-cache cef on all non hub interfaces

ip route-cache same-interface on hub interfaces

RJ