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Webcast-Catalyst9k
New Member

Router Interface down

How come when i set the fastethernet 0/1 for router to full duplex and connect it to the switch (full duplex also), the interface will down? It can only be up when set fastethernet 0/1 to half duplex?

4 REPLIES
New Member

Re: Router Interface down

If that is happening it seems that the switch you are connecting to might not be the same speed. Setting the interface to full duplex requires like interfaces on both sides (and/or higher interfaces on a remote side manually configured to match the speed on the local side and/or vice-versa).

Re: Router Interface down

Yes try as above mentioed.

Set full duplex on the router interface and the switch interface.

Still if it does not come up set both to auto and check.

setting it to auto will auto neigo the speed check in which speed it is up. half or full.

if still in half i would suggest to change the cable might help.

New Member

Re: Router Interface down

Currently, the port no is 20 on switch with vlan 120. May I know how to change it to duplex auto from switch?

I am quite new and just start to learn manage switch.

Re: Router Interface down

Below command will help

config t

int fa0/20

(config-if)#dup

(config-if)#duplex ?

auto Enable AUTO duplex configuration

full Force full duplex operation

half Force half-duplex operation

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