Re: ISO ES to IS Info Sought

Charles Hedrick (
Fri, 20 Mar 87 00:09:53 est

Yes, your theory is correct. You can make any network be treated as
local by doing
  route add <net> <yourhost> 0
(in 4.2. In 4.3 I think there is some minor difference, like omitting the
0.) I thought somebody had explained this before. 4.2 works like this:

   route-packet (destination-address)
        lookup destination-address as a host in host routing table
                [entries that show with "H" in flags field of netstat -r]
        if that fails, lookup network(destination-address) as a network
                in network routing table [entries without an "H"]
        if that fails, look for default route
        if that fails, say destination unreachable
        now we have a route.
        If the metric is 1 or larger [metric is the last field in the
                "route add" comment. You can tell from the route
                command because routes with a metric >= 1 will show
                a "G" in the flags field], this is a normal gateway
                entry. Send packet to the host listed in the
                gateway field.
        If the metric is 0 [route add command ended in zero, or in
                some versions, the metric was omitted. netstat -r
                does not show "G" in the flags field], this is a
                "route to the interface". Send packet out the
                interface listed in the interface column. If
                interface is an Ethernet, use ARP.

Note that the gateway address (gateway field in netstat -r) is
irrelevant in the case of a route to the interface. The route add
command uses that address only to figure out which interface to
associate with the route. So when setting up a route to an interface,
the simplest approach is to use your own address on that network.

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