The default gateway is deleted unexpectedly when you delete an additional IP address in Windows Vista or in Windows Server 2008
You delete an additional IP address from a network interface on a computer that is running Windows Vista or Windows Server 2008.
In this case, the default gateway is deleted unexpectedly.
Note: This issue occurs if you add the default gateway by using the route add -p command.
The following is an example scenario:
- You configure only the IPv4 address and subnet mask on a network interface:
Ethernet adapter Local Area Connection 1:
IPv4 Address. . . . . . . . . . . : 192.168.0.20
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . :
- You add a default gateway route entry with a persistent option by using the route command:
route add -p 0.0.0.0 mask 0.0.0.0 192.168.0.1
- You add an additional IP address to the network interface by using the netsh command:
netsh interface ipv4 add address “Local Area Connection 1″ 192.168.0.21 255.255.255.0
- You delete the additional IP address from the network interface by using the netsh command:
netsh interface ipv4 delete address “Local Area Connection 1″ 192.168.0.21
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB2469100.