Vanishing Subnet
Adding Persistent Routes Under Windows NT.
When a computer dials into the internet it's routing tables are reset to default to the internet IP address that is assigned to your modem. This will cause a problem if you have multiple subnets on your Local Area Network because the computer will lose all the routes to the other subnets. To fix this under Windows NT you can add a persistent route back to your local subnet.
A static entry should be added to the static router's routing table for all networks to which it has no configured interface. A static entry includes the following:
- Network Address: The network ID or network name of the destination network. If a network name is used for the destination, it is looked up in the NETWORKS file.
- Netmask - the subnet mask for the network address.
- Gateway Address - the IP address or host name of the interface to the destination network. If a host name is used for the gateway, it is looked up in the HOSTS file.
Use the route command to add static entries to the routing table.
| To add or modify a static route | Function |
| route add [network] mask [netmask] [gateway] | Adds a route |
| route -p add [network] mask [netmask] [gateway] | Adds a persistent route |
| route delete [network] [gateway] | Deletes a route |
| route change [network] [gateway] | Modifies a route |
| route print | Displays the routing table |
| route -f | Clears all routes |
For example, to add a route to enable persistent communications with network 131.107.24.0 from a host on network 131.107.16.0 via the gateway computer 131.107.16.2, you would run the following command:
-
route -p add 131.107.24.0 mask 255.255.255.0 131.107.16.2
