I am running a local network setup with two Linux machines (2.4.7 kernel), both running Samba 2.2.1, one of which is the WINS server and domain controller for the network. Both are more or less boxed configurations of RedHat 7.2. Additionally I have two Windows 2000 boxes on the network. When running over a dual-speed hub the setup works fine, and all the boxes can talk to one another. However, once I replaced the hub with the Kingston switch the Win boxes are no longer able to see the Linux boxes, and vice versa although each set of like boxes can see and talk to one another. A tcpdump of the network traffic while running nmblookup shows a few requests from the Samba machine, 19:05:00.142251 192.168.0.1.33770 > 192.168.0.3.netbios-ns: NBT UDP PACKET(137): QUERY; REQUEST; BROADCAST (DF) but no response from the Win box, and a packet capture on the Win box confirms that the traffic to the Win host is present but no reply is being attempted. I've successfully established UDP and TCP connections to the relevent ports on the Windows host to verify that both types of traffic work over the switch, and that the Win box is listening. Also, other UDP services work fine between the boxes, including DHCP. Another finding is that when running "nmblookup -B <win2000 machine name> '*'" as suggested in the "Diagnosing Samba" doc, it replies with the IP of the Samba server, but when I run "nmblookup -B <win2000 ip address> '*'" it replies that the name query failed. I've looked through all the Samba docs and troubleshooting guides I've found, searched the list archives, and tried a net search to no avail. The relevant portions of smb.conf are listed below. Has anyone seen this behavior before? Thanks for having a look. Craig W. Blake workgroup = workgroup netbios name = samba hosts allow = 192.168.0. security = user socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192 interfaces = 192.168.0.1/24 local master = yes os level = 64 domain master = yes preferred master = yes domain logons = yes wins support = yes dns proxy = no