I have a problem with a 2851 router connected to Microwave device. Line protocol goes up and down continuously on all interfaces. Microwave has 4 Ethernet connections plugged on a NM-16ESW of the router such as:
Fa1/1 on NM-16ESW <-> Ethernet1 of microwave
Fa1/2 on NM-16ESW <-> Ethernet2 of microwave
Fa1/3 on NM-16ESW <-> Ethernet3 of microwave
Fa1/4 on NM-16ESW <-> Ethernet4 of microwave
We have made Factory Acceptance Test before deployment where all was working well.
We tried all combination of speed (100M or Auto) and Duplex (Full or Auto) but problem still occurred.
We found a workaround (but non sustainable) by inserting a switch (3560) between Microwave and router: One link between router and switch, and the 4 Ethernet connection of Microwave on the switch.
The same problem occurred on a 2821.
Thank you for your assistance!