After the prerouter's routing tables have been built (as described in Initializing an AF_INET (IPv4) transport driver and Initializing an AF_INET6 (IPv6) transport driver), the prerouter can be notified about interface state changes in the following ways:

• For TPs that returned a value of -1 for Iocn_NetConfLength on the initial SIOCGIFCONF (or for NchNumEntryRet on the initial SIOCGHOMEIF6) during TD initialization, the prerouter's routing tables will contain both active and inactive routes. The TP can issue the following ioctls to change the state of an interface:
  • The SIOCMSMODHOMEIF ioctl allows a TP to activate or deactivate an IPv4 home interface. For each entry in the home IP address table, the Iocn_bRtAttrRtUp bit indicates the status (active or inactive) of the home interface. SIOCMSMODHOMEIF turns this bit on or off to activate or deactivate the interface. If a home IP address is active, then this means that the home interface and all of the routes associated with that interface are active. Likewise, if a home IP address is inactive, then the home interface and all of the routes associated with that interface are inactive.
  • The SIOCMSMODHOMEIF6 ioctl allows a TP to activate or deactivate an IPv6 home interface. For each entry in the home interface index table, the IPV6BitRtUp bit indicates the status (active or inactive) of the home interface. SIOCMSMODHOMEIF6 turns this bit on or off to activate or deactivate the interface. If an interface is active, then all of the routes associated with that interface are active. Likewise, if an interface is inactive, then all of the routes associated with that interface are inactive.
• Otherwise, for TPs that did not return a value of -1 for Iocn_NetConfLength on the initial SIOCGIFCONF (or for NchNumEntryRet on the initial SIOCGHOMEIF6) during TD initialization, the prerouter only adds the active routes to its routing tables. Therefore, the fact that a route exists in the routing tables means that the interface is active. If the state of an interface changes, the prerouter receives an SIOCMSRBRTTABLE ioctl (for IPv4) or SIOCMSRBRT6TABLE ioctl (for IPv6) from the TP so that it can rebuild its routing tables, as described in Rebuilding the routing tables.