Defining NIM routes

NIM uses routing information internally to ensure that a client on one network can communicate with a server on another network. It defines the gateway to use to go from one network to the other network.

NIM provides the ability to define default or static routes. Default NIM routes provide the following advantages over static routes:
  • They more closely model the network configuration of common network environments.
  • They permit resources that are distributed throughout a NIM environment to be more easily accessed by any client in the NIM environment.

To determine the gateway used by machines on a given network, run netstat -rn on a running machine on the network to see if a default gateway is listed. You can also issue traceroute Host_Name from a running machine on the network in question, where Host_Name is the name of the master's primary network interface if determining the gateway for a client, or the name of a target client if determining the gateway used by the master. The first gateway listed is the gateway used by machines on the specified network.

Note that NIM routes are not required if the only networks defined in a NIM environment are associated with interfaces (if attributes) defined on the NIM master and if all resources will be defined on the master. If resources are served by machines other than the master to clients that do not reside on the same network as the server, NIM routes are required between those networks even if all networks are attached to interfaces belonging to the master. In this case, the master must act as a gateway (with IP-forwarding switched on), and the host name of the interface on the master should be used as a gateway.

Networks with default routes may be created automatically when NIM machines are being defined.

Communications between networks go through several gateways. However, it is important to remember that when defining NIM routes for networks, the only gateways of interest are the first ones used by the networks to reach their destinations. Intermediate gateways between the originating and destination networks are irrelevant for NIM routing purposes.