cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
620
Views
0
Helpful
3
Replies

Cisco Express Forwarding (CEF)

curtis03_2
Level 1
Level 1

I recently configured several 3725 routers with the IP CEF command. When installed, trafffic slowed dramatically, with packets dropping everywhere between these routers.

Immediately the command was removed, traffic returned to normal.

Does anyone have any knowledge of the workings and effects of utilising IP CEF?

Many thanks in advance

3 Replies 3

Hello,

which IOS version are you running ? Can you post your configuration(s) ?

Regards,

Georg

Hello Georg

Config as follows: -

version 12.3

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

!

hostname xxxxxxxxxxx

!

boot-start-marker

boot-end-marker

!

enable secret xxxxxxxxxxxxxxxxxxxxxxxx

!

clock summer-time BST recurring last Sun Mar 2:00 last Sun Oct 2:00

no aaa new-model

ip subnet-zero

!

!

!

ip domain name xxxxxxxx

ip name-server xxxxxxxx

ip name-server xxxxxxxx

no ftp-server write-enable

!

!

!

!

interface FastEthernet0/0

description **PSN switch Clarence Crt**

ip address xxxxxxxx 255.255.255.252

duplex auto

speed auto

!

interface Serial0/0

description **Link to Eliz House**

bandwidth 2048

ip address xxxxxxxx 255.255.255.252

no ip mroute-cache

no fair-queue

!

interface FastEthernet0/1

description **100Mb LES circuit to Queens Crt**

ip address xxxxxxxx 255.255.255.252

speed 100

full-duplex

!

interface Serial0/1

description **Link to lincoln Bldgs**

bandwidth 2048

ip address xxxxxxxx 255.255.255.252

!

interface FastEthernet1/0

description ***100Mb LES circuit Causeway***

ip address xxxxxxxx 255.255.255.252

speed 100

full-duplex

!

interface FastEthernet1/1

description ***10Mb LES circuit VicHall***

ip address xxxxxxxx 255.255.255.252

speed 10

half-duplex

!

router ospf 100

log-adjacency-changes

network xxxxxxxx 0.0.0.0 area 0.0.0.0

network xxxxxxxx 0.0.0.0 area 0.0.0.0

network xxxxxxxx 0.0.0.0 area 0.0.0.0

network xxxxxxxx 0.0.0.0 area 0.0.0.0

network xxxxxxxx 0.0.0.0 area 0.0.0.0

network xxxxxxxx 0.0.0.0 area 0.0.0.0

!

ip classless

xxxxxxxx

xxxxxxxx

xxxxxxxx

xxxxxxxx

xxxxxxxx

no ip http server

!

snmp-server community xxxxxxxx

snmp-server enable traps tty

!

line con 0

password xxxxxxxx

login

line aux 0

password xxxxxxxx

login

line vty 0 4

password xxxxxxxx

login

!

ntp clock-period 17180696

ntp source FastEthernet0/0

ntp server xxxxxxxx

!

end

thanks

Hello,

your config looks ok, I also could not find any CEF-related bugs. Is there a specific reasons why you only advertise host addresses in your OSPF, while your interfaces have /30 subnets ? Can you try and advertise the networks:

network xxxxxxxx 0.0.0.3 area 0.0.0.0

network xxxxxxxx 0.0.0.3 area 0.0.0.0

network xxxxxxxx 0.0.0.3 area 0.0.0.0

network xxxxxxxx 0.0.0.3 area 0.0.0.0

network xxxxxxxx 0.0.0.3 area 0.0.0.0

network xxxxxxxx 0.0.0.3 area 0.0.0.0

and then turn on CEF ?

Regards,

Georg