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New Member

GigabitEthernet Card on Cisco 3825 router

Hi,

I have gbit interface card on Cisco 3825. Can I configure and set the interface to 100 Mbps full duplex and the switch are also configured as 100Mbps full duplex ?

Here is the configuration on the router :

interface GigabitEthernet0/0

duplex full

speed 100

media-type rj45

negotiation auto

Thanks..

Joseph

4 REPLIES

Re: GigabitEthernet Card on Cisco 3825 router

Hi Joseph,

Yes, no problem, but a little note here, when you set the speed to 100 and the duplex to full, then the router will automatically do "no negotiation auto" as it is of no meaning now.

BR,

Mohammed Mahmoud.

New Member

Re: GigabitEthernet Card on Cisco 3825 router

Ok. Thanks. But what if the switch port configuration is different for example, duplex auto and speed auto configured ? Will this create a problem ?

On the router :

speed 100

duplex full

On the switch :

speed auto

duplex auto

Thanks.

Joseph

Re: GigabitEthernet Card on Cisco 3825 router

Hi Joseph,

This will create a problem, since the switch will try to negotiate the duplex, and the router will never negotiate since it is manually configured, causing the switch to default to half duplex, and you'll face a duplex mismatch issue (the switch detects the speed anyway based on the incoming electrical signal, and there won't be a speed issue). The only special case i believe would be if the switch interface is GE not FE, and in this case the switch will default to full duplex (which can also create a duplex mismatch if the other side is manually configured to half duplex, not in your case).

BR,

Mohammed Mahmoud.

New Member

Re: GigabitEthernet Card on Cisco 3825 router

Hi Mohammed,

How about this scenario of configuration on the router which has the following setup :

interface GigabitEthernet0/0

speed 100

duplex 100

On the switch, it has the following configuration :

interface GigabitEthernet3/44

switchport

switchport access vlan 5

Will the above configuration cause duplex mismatch issue ?

Thank you.

Joseph

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