Oliver Joa writes:
> I have tried to figure out what the pointopoint flag
> of ifconfig is used for, but I have not found any
> sense?
> What can be done with that?
Look at the definition of ifaddr in <net/if.h>. ifa_ifu contains a
union for either the broadcast address associated with an interface on
a network that supports broadcasts (e.g. an Ethernet), or the
destination address associated with an interface that reaches only one
other place (e.g. a PPP or SLIP link).
Broadcast networks have certain topological restrictions, such as you
can't have two Ethernet interfaces with addresses on the same network
or subnet. Routing decisions on broadcast networks examine the
interface's address and subnet mask to know whether a packet's
destination is reachable via ARPing or routing.
There's no reason to ARP on a point-to-point link, and no need for a
broadcast address, since there's only one other system on the link.
Instead, ifa_ifu contains the address through which packets may be
routed. There's no topological restriction against duplicated local
addresses. This means you can have many point-to-point links, each
with the same local address, distinguished in the routing table by
their differing destination addresses (ifa_dstaddr). This simplifies
the configuration you might tell remote users who dial into you for
PPP service.
--
Bob Sutterfield +1 909 794 1151
Mission Aviation Fellowship / MAFlink Tech
mailto:[EMAIL PROTECTED] http://www.XC.Org/bob
Pray Globally - Serve Locally
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