My provider (Deutsche Telekom) is only able to hand over a 1Gbps-Link with speed und full-duplex configured fix.
To force the router (cisco 3945) for 1000/full, I had to remove the 'media-type sfp'
SFP is MM-SX on Router-Interface Gi0/2
This configuration worked a while but shows many interface resets (more than 30 in one minute).
Telekom confirmed, their connection is working properly.
After switching the router off an on, I could no longer connect with telnet or ssh. Ping is also not successful but cdp shows the neighbor router!?!
Maybe this is a problem with SFP and duplex configuration.