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Why cisco uplink interface not coming up on auto mode but on 100 mpbs

hardipdhillon
Level 1
Level 1

Why cisco uplink interface not coming up on auto mode but on 100 mpbs hardcoded.

4 Replies 4

Herald Sison
Level 3
Level 3

what switch model are you using on both sides? have you checked both switch's port speed and duplex config?

one side is cisco 1941 router and other side is 3850 switch. Both have Gig Ports and tried all speed and duplex combinations. if i keep auto speed and duplex setting then port is not coming up. Both its coming up on 100 Mbps hard coded

If the patch cable used to connect the router and the switch only has Pairs A and Pairs B, then the port will only negotiate to 100 Mbps. 

NOTE:  Do not bother to run a TDR from a 3850 because there is a TDR bug and will affect reliability.

In that case will interface remain down if speed is auto

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