Setting up subnets and routing

Configuring router discovery using routed

The routing daemon, routed(1Mtcp), in UnixWare^® 7 implements router discovery as its default behavior. A UnixWare 7 non-routing host running routed will send out router discovery solicitation messages. A UnixWare 7 router (a system with more than one network interface configured, and with ipforwarding and ipsendredirects set to 1) running routed will advertise its routing tables and respond to router discovery solicitation messages.

Router discovery may be turned off on a host by specifying the no_rdisc keyword in the /etc/inet/gateways file.

NOTE: Systems that are configured with both a LAN connection and a WAN connection (using a point-to-point protocol such as SLIP or PPP) may also be acting as routers to external networks such as the Internet. By default, routed only listens for router discovery messages on point-to-point links; it does not send advertisements and solicitations over such links.

To enable advertisements on point-to-point links, specify rdisc_adv in /etc/inet/gateways. To enable solicitations on point-to-point links, specify send_solicit in /etc/inet/gateways.

If you configure non-routing hosts to only use router discovery, you must also configure the routers on the local network to listen for router discovery solicitations and to send advertisements.

On non-routing hosts, routed keeps track of received router advertisements, adding a default route for the highest preference route. For this reason, multiple routers running router discovery on the same subnet should use different preference values. A preference value is an integer greater than 0. The most preferred route should have the highest preference value. You should not configure a router to advertise a route on an interface if this might lead to inefficient routing of packets through the local subnets.

The following example entries from a router's /etc/inet/gateways cause routed to advertise a route with a preference of 10 on the subnet connected to the net1 interface, but not to advertise on the subnet connected to the net0 interface:

   if=net0 no_rdisc_adv
   if=net1 rdisc_pref=10 rdisc_interval=45

In this example, the interval between sending router discovery advertisements is set to 45 seconds. This value is substantially lower than the default interval of 1800 seconds (30 minutes) to allow non-routing hosts to update their default route more frequently.

If some routers on a subnet implement router discovery while others do not, or if identical or incorrect preference values are configured on the routers, this may cause non-routing hosts to install an incorrect default route.

To disable router discovery on routers and non-routing hosts running routed, add the following line to /etc/inet/gateways:

   no_rdisc

Restart routed by killing its process and rerunning in.routed. Alternatively, shut down and reboot the router.

See routed(1Mtcp) for more information about the configuration of router discovery in routed.