Some info needed!!

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Jul 19th, 2007
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Hi to all,

I read about CEF and it has to be enable in order to do per-packet load balancing (PPLB). However, while it works fine on routers, i dont know if CEF allows PPLB on multilayer switches. I came across this bit of info from a document entitled "Configuring Cisco Express Forwarding" [XC-29-XC-32, Cisco IOS Switching Services Configuration Guide]

"Note Per-packet load balancing via CEF is not supported on Engine 2 Gigabit Switch Router (GSR) line cards (LCs)."

Can someone pls explain the above statement to me. I understood it as saying that PPLB via CEF is not allowed on multilayer switches. Is there a document that states whether PPLB via CEF is allowed on multilayer switches?

One thing more, what is the maximum number of Fast Ethernet ports in existing Cisco routers?Which Cisco router is that?

Warm regards,


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mohammedmahmoud Thu, 07/19/2007 - 10:39
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Layer3 switches do CEF in HW, and thus not supporting PPLB is a hardware limitation, unlike Router which does CEF using the CPU (although some of the high end routers do CEF in hardware like the GSR), and for example in the case of the catalyst 6500, PPLB on MSFC2/MSFC3 apply only to traffic that is CEF-switched on MSFC/MSFC3 (CPU) it does not affect traffic that is switched by CEF for PFC2/PFC3 on the supervisor engine.

As for routers Fast Ethernet port density, all the modern routers can take switch modules now, but i guess that the 7600 would be the most Cisco router supporting FastEthernet ports.

Always use the Cisco Router Guide:

And the Cisco Switch Guide:


Mohammed Mahmoud.


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