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Cisco Express Forwarding???

A customer of mine has a 2600 that provides internet connectivity that has dual t1's that are load balanced ( ip load-sharing per-packet) on each interface.

The ISP manages the router but I have full access. They have "ip cef" configured globally but at (all) each interface they have issued the "no ip route cache" command wich I know for fact effectivly shuts off CEF on the interface and have verified this by using the "sh cef interface" command.

The article I read provided by Cisco (IOS Essentials 2-9.pdf) states that cef is the preferred way of switching and that it will be enabled by default in future releases. SO if this is the case why enable globally and disable at each interface. Is this a mistake on their behalf and possibly shut off unintentionally or could there be a reason that I do not know about?

TIA

Paul

3 REPLIES
Silver

Re: Cisco Express Forwarding???

Paul,

In the past this "no ip route-cache" was used to get per packet load sharing, since CEF load shares, by default "per destination" and not "per packet". There have been improvements to this load sharing to allow user to configure per packet using CEF... ip load-sharing per-packet on the interface.

Check out this URL for more information:

http://www.cisco.com/en/US/partner/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a00800ca6ca.html#33184

Hope this helps you,

Don

New Member

Re: Cisco Express Forwarding???

It might be a securtiy reason that they enabled CEF globally, prevent spoof attact.

New Member

Re: Cisco Express Forwarding???

Don,

Great article on load balancing when CEF is enabled, thanks!!!

I went ahead and issued "ip route-cache cef" at each interface to take advantage of CEF and left balancing on as "per packet" since no realtime traffic is being used. It ensures absolute balancing.

Thanks to all who replied, this certainly is a great rescource!

Paul

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