Network packet size can cause trouble

Last week gave me insight into network packet sizes that I thought I would never need to bother my head with.

That is, one of the PCs I need to administer suddenly failed to login to an domain user account properly.

Yes, we had modified the network packet size (frame buffer size) of the network interface card (NIC) to a somewhat lesser value for our switch was not operating properly with jumbo-sized packets.

After the change, this single PC failed to login, and it took even very long for it to figure that out.

Naturally, Google gave wild answers to this problem, but nothing seemed to help. Finally, we reset the network packet size back to close the original value (we had dropped it to 1K for testing), and suddenly everything worked fine.

The lesson: if you fiddle with network packet sizes, Windows Active Directory might not like it. Solution: make sure the server and the workstation have the same packet size! Good luck...