Solved: Cisco 1720 FE Default Duplex Setting

johnlloyd_13 · ‎04-07-2010

hi experts,

i've got a cisco 1720 router. would like to know what is the default duplex setting for FE port?

cisco 1720 (MPC860) processor (revision 0x501) with 12288K/4096K bytes of memory.
Processor board ID JAD041306KV (1507224326), with hardware revision 0000
M860 processor: part number 0, mask 32
Bridging software.
X.25 software, Version 3.0.0.
1 FastEthernet/IEEE 802.3 interface(s)
1 Serial(sync/async) network interface(s)
32K bytes of non-volatile configuration memory.
4096K bytes of processor board System flash (Read/Write)

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1720#sh run int f0
Building configuration...

Current configuration:
!
interface FastEthernet0
description Customer Network
ip address X.X.X.X 255.255.255.224
no ip route-cache
no keepalive
speed auto
no cdp enable
end

Leo Laohoo · ‎04-07-2010

How about "no full-duplex"? Make sure you set your speed to auto.

View solution in original post

Federico Coto Fajardo · ‎04-07-2010

Hi,

The default duplex setting is to auto-negotiate.

You can check doing a ''sh int fas 0'' instead than ''sh run int fas0''

Federico.

johnlloyd_13 · ‎04-07-2010

thanks federico! i've configured this port for full-duplex and now want to revert back to auto-negotiate (default). could you assist how to revert back?

1720#sh run int f0
Building configuration...

Current configuration:
!
interface FastEthernet0
description Customer Network
ip address X.X.X.X 255.255.255.224
no ip route-cache
no keepalive
speed 100
full-duplex -->
no cdp enable
end

Leo Laohoo · ‎04-07-2010

Try "speed auto" and then "duplex auto". I believe this IOS is one of those "if it's default, it won't appear" concept.

Ganesh Hariharan · ‎04-07-2010

thanks federico! i've configured this port for full-duplex and now want to revert back to auto-negotiate (default). could you assist how to revert back?

1720#sh run int f0
Building configuration...

Current configuration:
!
interface FastEthernet0
description Customer Network
ip address X.X.X.X 255.255.255.224
no ip route-cache
no keepalive
speed 100
full-duplex -->
no cdp enable
end

Hi,

Configure with below mentioned steps for auto configuration

Step 1 Router# configure terminal
Step 2 Router(Config)# interface ethernet 0/11
Step 3 Router(Config-if)# speed auto
Step 4 Router(Config-if)# duplex auto

Hope to Help !!

Ganesh.H

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johnlloyd_13 · ‎04-07-2010

hi ganesh,

thanks for your inputs! however, this router doesn't support the command you've mentioned. is there a workaround to set the interface to "duplex auto"?

1720(config)#int f0
1720(config-if)#dup?
% Unrecognized command

1720(config-if)#full-duplex ?

1720(config-if)#half-duplex ?

Leo Laohoo · ‎04-07-2010

How about "no full-duplex"? Make sure you set your speed to auto.

johnlloyd_13 · ‎04-07-2010

awesome! it worked! thank you!

1720(config-if)#no full-duplex ?

Leo Laohoo · ‎04-08-2010

Thanks for the rating.