Ethernet port speed problem in 3750

Unanswered Question
Jan 27th, 2008


I m Shubhangi Sakpal, I am managing the LAN of Reliance Ind.

I am facing the problem with ethernet port. The specific port works on only 10mbps half duplex speed.

Can u guide me, how to get 100mbps speed on this specific port.

I have this problem too.
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ajagadee Sun, 01/27/2008 - 23:41

What is current setting on the port that you are having issue with. Also, can you post a copy of the "show run interface xxx", so we can see what is configured currently. Also, what is connected on the other end of the port.

Please refer the below URL for information on Speed/Duplex settings.

Configuring Interface Speed and Duplex Mode

Catalyst 3750 Series Switches Troubleshoot Common Issues



** Please rate all helpful posts **

shubhangi.sakpal Mon, 01/28/2008 - 00:02

Dear Sir,

Pls find the attachment, which contains the sh int status of that specific port.

Ith current speed setting on that perticular port is speed: auto, Duplex : auto

dongdongliu Mon, 01/28/2008 - 01:00

can you show us "sh run int fa4/0/12"?

what is the another equipment connected 3W_Cabin32`s f4/0/12?

if the another equipment is also cisco that is also 100M port,speed: auto, Duplex : auto

may be you need type a command below:

speed 100

shrikar.dange Mon, 01/28/2008 - 01:02


ASFAIK that manual config of 100 Mbps @ full duplex do not interact properaly with interfaces configd with auto.This is because as per 802.3u standard both interfces recuire to send auto-negoatiation parameters for link only when both ends are confgd for auto-neg.If one end is hard coded then there will b duplex mismatch resulting errors and resulting switch interface to operate in half duplex.

As cisco recomondes always manually confgd 10/100-Mbps fastethernet & 10/100/1000Mbps gig ethernet on both link ends for critical connections to servers or 3rd party equipment.

Use auto-neg for interconnecting cisco devices and user workstations.Please check the other end settings and if possible do set the speed and duplex settings manually @ both ends.



shri :)

shubhangi.sakpal Mon, 01/28/2008 - 01:51


The int fa4/0/12 is connected to desktop pc. & the speed on the both the ends are set to Auto mode.

whem i m changing the spped as 100mbps on both the ends, i get the result on desktop as LAN Not connected.

shrikar.dange Mon, 01/28/2008 - 02:02


does that desktop nic supports 100 mbps speed? put the interface in shut mode change the settings @ both ends see if this helps.



shubhangi.sakpal Mon, 01/28/2008 - 02:06

ok. i will try this first & contact u again.

But can it possible that the specific port got currupted & hence i m getting 10 mbps speed.

shubhangi.sakpal Wed, 02/13/2008 - 22:52


I tried the all the possible ways suggested by u, But still that ethernet port is working on 10mbps.

Can it be possible that the port has got malfunction?

shubhangi.sakpal Wed, 02/13/2008 - 23:47

Now i m getting 100 mbps speed. Manually i shut that port for 7 days. & today again that port status has changed manully to Up.

so now i m getting 100 mbps speed. & i have kept that port under observation.



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