Broadcom IPV4 Large Send Offload
I have run into a couple of scenarios where this setting has caused issues and hence decided to blog about it.
- Windows 2008 X64 based domain controllers didn’t replicate with each other. However they were pulling updates inbound from other DCs (that happened to be Windows 2000 Server based) fine. Running commands such as repadmin /bind <W2k8DCname> and /replsum switches indicated replication failed with access denied. Additionally terminal server sessions –(remote admin mode) were dropped repeatedly within milliseconds of establishing a session. It turned out that the newly built Windows 2008 based DCs had Broadcom cards in them and the driver installer enabled the above setting. Once this was turned off, everything started working perfectly.
- Was at a customer recently that claimed when they made their Windows 2003 X64 DC in a single domain forest a GC, after a while the server was unresponsive to certain RPC traffic. once the server was removed from been a GC and rebooted, it would not cause issues. I didn’t believe them at first but then they demonstrated by configuring the DC to a GC role. Sure enough a few hours later the server was having issues. repadmin /bind <dcname> traffic once captured over netmon showed resets immediately. dir \\dcname\c$ and other SMB share access access such as SYSVOL and same DC worked. LDAP and GC traffic was perfect. However repadmin based commands like /bind, /replsum did not work. portqry commands to port 135 failed (unfortunately I don’t have error details at the moment). Once the above setting was turned off on the NIC and server was rebooted, no further recurrences were noted.
So in case you run into issues where “RPC traffic is not responded to properly”, check and disable the above setting if configured on your server NIC. Please post a comment if you run into similar issues resolved by this setting.
Thanks
M