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Community Member

Strange CEF Behavior?

Is there any valid reason that "sh ip cef x.x.x.x" would yield results different from the output of "sh ip cef"?

I have a situation where this is the case, and while the system should be using the path shown with "sh ip cef" it is actually trying to use the incorrect path displayed with "sh ip cef x.x.x.x"


(Actual output, scrubbed for privacy)


ROUTER#sh ip cef x.x.42.66

x.x.32.0/20, version 259912, epoch 0, cached adjacency y.y.192.129

0 packets, 0 bytes

via y.y.192.161, 0 dependencies, recursive

next hop y.y.192.129, GigabitEthernet2/0 via y.y.192.161/32

valid cached adjacency

ROUTER#sh ip cef | beg x.x.3

x.x.30.0/24 z.z.112.9 GigabitEthernet0/2

x.x.32.0/20 z.z.112.9 GigabitEthernet0/2 <<<Match>>>

x.x.32.0/21 z.z.112.9 GigabitEthernet0/2

x.x.32.0/24 z.z.112.9 GigabitEthernet0/2

x.x.33.0/24 z.z.112.9 GigabitEthernet0/2

x.x.34.0/24 y.y.192.129 GigabitEthernet2/0

x.x.35.0/24 y.y.192.129 GigabitEthernet2/0

x.x.36.0/24 y.y.192.129 GigabitEthernet2/0

x.x.37.0/24 z.z.112.9 GigabitEthernet0/2

x.x.38.0/24 z.z.112.9 GigabitEthernet0/2

x.x.39.0/24 z.z.112.9 GigabitEthernet0/2

x.x.44.0/24 z.z.112.9 GigabitEthernet0/2


Re: Strange CEF Behavior?

Cisco Express Forwarding (CEF) is advanced, Layer 3 IP switching technology. CEF optimizes network performance and scalability for networks with large and dynamic traffic patterns, such as the Internet, on networks characterized by intensive Web-based applications, or interactive sessions.

Refer the following url for more info on CEF configuration and troubleshooting:

Community Member

Re: Strange CEF Behavior?

Thanks but the problem appears to have been a glitch in the IOS version that was in use, as a downgrade resolved my issue.

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