I have an ethernet link between a 1812 on interface fast ethernet 2 and a 1811 on interface fast ethernet 0. Both interfaces are configured to full duplex 100 Mbit and I use a straight ethernet cable. Occasionally the line protocol refuses to go up after a reboot and I cannot access the remote 1811 router. The 1812 router will answer if I send a ping to the ethernet interface but I get no answer from the 1811 interface. The IOS-versions used are 12.4(6)T5 on the 1812 and 12.4(11)T1 on the 1811. Is this a bug in IOS? Any info or help will be appreciated.