I had a weird issue on a Cisco 2911 router where we installed a EHWIC-1GE-SFP-CU and the link came up when we plugged in the cable but when we disconnected and reconnected the status would go down and get stuck down. I am sure this is the same across the entire 2900 range.
description **SIP Trunk Link**
ip address 192.168.0.1 255.255.255.0
ip nat inside
ip virtual-reassembly in
This card has a SFP and RJ-45 slot and it turns out we needed to specify the media type by using this command:
Port now comes back online fine. Never had this issue before and we are on the latest version of the IOS
(C2900-UNIVERSALK9-M), Version 15.3(1)T