Cisco 1720 FE Default Duplex Setting

Answered Question
Apr 7th, 2010
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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)


----------


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

Correct Answer by Leo Laohoo about 6 years 11 months ago

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

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Federico Coto F... Wed, 04/07/2010 - 21:30
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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 Wed, 04/07/2010 - 22:01
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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 Wed, 04/07/2010 - 22:42
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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 Wed, 04/07/2010 - 22:59
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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 Wed, 04/07/2010 - 23:24
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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 ?

Correct Answer
Leo Laohoo Wed, 04/07/2010 - 23:32
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How about "no full-duplex"?  Make sure you set your speed to auto.

johnlloyd_13 Wed, 04/07/2010 - 23:38
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awesome! it worked! thank you!


1720(config-if)#no full-duplex ?
 

Leo Laohoo Thu, 04/08/2010 - 00:41
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Thanks for the rating.

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