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CEF or Fast Switched on a router - how can you tell

Can anyone please confirm the following for me please then.

Is fast switching is automatically enabled when CEF switching is enabled? Is there is no way to take fast switching off but leave CEF on, so that a CEF punt, does not get punted to fast switching (builds a route-cache entry) and then get pushed from fast switching to process switching?

It actually gives us a benefit in the way it is right now (for troubleshooting), Ie the IP route-cache flags being Fast and CEF on an interface, and then you can tell what packets are being punted from CEF as it then builds a fast switching route-cache entry because you cannot tell the difference between a packet that is CEF switched, or fast switched in the output of the show interface stats (can you?)

IE, if we have a packet that is going to be NATd (ie has to get processed switched), and as the show interface stats show fast and CEF switched packets in the same output (cannot distinguish between them in the output), you can tell which destination routes have had to get punted from CEF (ie, CEF cannot deal with it) as they then build a route-cache entry (which I assume does not get used to switch the packets), and THEN get pushed through to process switching.

The main question being, would there be any performance gain, if a CEF punted packet COULD go straight to processed switching, rather than getting punted from CEF, to FAST switching and THEN onto process switching. IE, bypassing the extra layer of switching to get to process switching.

Single2#sh ip int e0/0

Ethernet0/0 is up, line protocol is up

Internet address is

Multicast reserved groups joined:

Outgoing access list is not set

Inbound access list is not set

Proxy ARP is disabled

Local Proxy ARP is disabled

Security level is default

Split horizon is enabled

ICMP redirects are never sent

ICMP unreachables are always sent

ICMP mask replies are never sent

IP fast switching is enabled

IP fast switching on the same interface is disabled

IP Flow switching is disabled

IP CEF switching is enabled

IP CEF Fast switching turbo vector

IP multicast fast switching is enabled

IP multicast distributed fast switching is disabled

IP route-cache flags are Fast, CEF

Router Discovery is disabled

IP output packet accounting is disabled

IP access violation accounting is disabled

TCP/IP header compression is disabled

RTP/IP header compression is disabled

Policy routing is disabled

Network address translation is disabled

WCCP Redirect outbound is disabled

WCCP Redirect inbound is disabled

WCCP Redirect exclude is disabled

BGP Policy Mapping is disabled


Single2#sh int stats


Switching path Pkts In Chars In Pkts Out Chars Out

Processor 8490733 847529764 10412718 930487166

Route cache 8156 1080586 76691 11763246

Total 8498889 848610350 10489409 942250412


Single2#sh int switching

Ethernet0/0 Routed link to SingleSwitch

Throttle count 0

Drops RP 0 SP 0

SPD Flushes Fast 0 SSE 0

SPD Aggress Fast 0

SPD Priority Inputs 8074469 Drops 0

Protocol IP

Switching path Pkts In Chars In Pkts Out Chars Out

Process 8057074 691313433 7557050 636369143

Cache misses 1534468 - - -

Fast 8156 1080586 76691 11763246

Auton/SSE 0 0 0 0

Would this be a correct assumption on the way the switching on a router works?

Kindest regards,