🚀 go-pugleaf

In article <33a9bc41.2603504@news.demon.co.uk>,
	matt@gumbley.ANTISPAM.demon.co.uk (Matt J. Gumbley) writes:

> that of the destination. If they match, the datagram is sent. If they
> don't match, how do I send the datagram to a gateway - where does the
> gateway's IP address go? Certainly not in the IP header's destination
> address... or do I just send the datagram over the SLIP link,
> addressed to the eventual destination, and expect the gateway to see a
> datagram destined for another network, and so route it accordingly?

What would be the point of including the gateway IP address in an IP
packet? (Ignoring source routed packets...) The gateway is by definition
the next hop, and must therefore be on the same network, so addressing it
at the network level would be pointless. As I understand it in the case of
ethernet you simply use ARP to get the ethernet address of the gateway
from its IP address, and send the packet as is to that ethernet address,
in the hope that the gateway will know what to do with it next.  The
gateway doesn't need to be told what its own IP address is!

In the case of SLIP and PPP it's even easier as the next hop is just
the other end of the link. i.e. just chuck the packets at the other end
of the link as they are.

Regards,
Ben.
-- 
/  Ben McKeegan                   http://www.fitz.cam.ac.uk/ben/  \
\  Fitzwilliam College, University of Cambridge, UK.              /