On 17/06/02 08:41 -0000, Amitava Sen wrote: > Dear Kumar, > > Simply put a GATEWAY is the out/in path for IP packets > from a network to another. DEFAULT GATEWAY means that > it is the first IP that the app should send to to reach outside > networks. You can have multiple GATEWAYS. In that case A default gateway is the LAST gateway. It is also known as the gateway of last resort.
Routing involves checking for the ip address in a table, figuring out the most specific route and sending the packet to the corresponding router on the corresponding interface. The most specific match wins, so if you have a /24 and two /25 routes for the same block, then the /24 is worthless since the /25s will always override. The default gateway has a mask of 0.0.0.0, implying a least specific route. > if you check the routing table on any node you will see > them listed along with a METRIC number, the DEFAULT > GATEWAY will have the lowest. Your apps would try > sending packets to outside networks starting with the lowest > and if failed try the next highest metric. > In your case the what I can see is that your m/c is acting as > your gateway for your LAN. One NIC has your PRIVATE > address and the other has a PUBLIC. First your m/c should > know that all packets NOT of private address should be > handed to the NIC[Public] -- enable IP forwarding. > Second all nodes should have the address of the > NIC[Private] as their DEFAULT GATEWAY. > > So, it works like this. NODE1 wants to send a packet to > www.pcquest.com, looks up its routing table, gets the IP of > the DEFAULT GATEWAY and send it there. Now your > gateway m/c on receiving the packet just forwards it to the > NIC[Public]. NIC[Public] forwards it to the router for actual > delivery. Of course, you forgot to mention the need for masquerading here (translating RFC 1918 address space to publically routable address space). The working is more like: The machine looks up the ip address of www.pcquest.com, looks for a route to that address. If it does not find a specific route, it sends the packet to the default gateway, which is supposed to know how to handle that packet. Devdas Bhagat ------------------------------------------------------- Sponsored by: ThinkGeek at http://www.ThinkGeek.com/ _______________________________________________ linux-india-help mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/linux-india-help
