Windows clients cannot access machine running DHCP server

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http://serverfault.com – I'm trying to setup a small LAN, using an Ethernet switch, an Arch Linux server, and around 10 Windows XP machines. This network has no outside connections. The Arch machine has a self configured ip address (configured with ip addr add dev eth0), and acts as a DHCP server(using dhcpd). This portion works great, windows clients get IP addresses, the correct gateway settings, perfect. However, the clients cannot connect to each other, or to the dhcp server. When I run ping on any client, I get no response, same happens if I try to ping any other client. On the gateway ()