Routing and switching with Cisco Catalyst 3550

[bogpsycho]

Hello everybody ! I use a Catalyst 3550 for routing and switching my clients to the Internet. I established a BGP session with an ISP which give me a default route for Global Access and full routing table (BGP) for Metro Access. At the moment everything is going fine, but the memory resources are low.  My question is : Is it possible to disable CEF on the switch port that is connected to the ISP ? And in this way the switch doesn't build a switching table with the bgp routes that it receives ? I receive from the ISP about 10k of metro routes and the installed memory on the switch is 64/8 MB.

Thank you in advance.

[Calin C. · Accepted solution]

If you really want, you can disable CEF on the interface like this:

conf t

int fax/y

no ip route-cache cef

Then you can check if it's disabled:

sw3-c3550#sh ip int fa0/1 | i CEF
  IP CEF switching is disabled
  IP route-cache flags are Fast, No CEF

Here:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094a83.shtml

You'll find an interesting article about how to  "Achieve Optimal Routing and Reduce BGP Memory  Consumption"

[j-marenda]

Calin,

You should not disable CEF on the Layer-3-Switch since this will disable hardware-based Layer3-Routing.

To process-switch traffic, the CPU in the 3550 is much too small.

Also, a Cat 3550 does not have sufficient memory to keep a bgp full-table, or two of them.

I would suggest to use at least one or a pair of  2821 router with 1GByte of Ram to do so,

(of course better a pair of 7201 with 2GByte of RAM).

Today, CEF ist working fine in most IOS Versions and many Cisco-uniqe features rely on it.

You may disable soft-config do save memory in BGP.

But iff you have just one upstream, you do not need BGP-full tables but only default-route,

and inject your own prefix. (You do not need bgp or an AS for that with just one connection).

just my 0.01 $,

Juergen.

[Calin C.]

Juergen, I know that everybody's advice is to use CEF, and this would be the best, if possible. In some cases, you have to deal with the hardware that you have and I just answer to the original question, how and if CEF can be disabled on Cisco 3550.

Cheers,

Calin