Rudiments of Routing
Rudiments of Routing Moving bits from the source to the destination is a major function of computer networking. On the current Internet, the Network layer is responsible for achieving this. AS 2 AS 1 Inter-domain routing OSPF and RIP Inter-domain routing OSPF and RIP Intra-domain routing BGP In general, most routing within Autonomous Systems use Routing Information Protocol (RIP), or its enhanced version Open Shortest Path First (OSPF). The current de facto Intra-domain routing standard is Border Gateway Protocol(BGP), Version 4. You need to concern yourself with these protocols if you are dealing with routers inside or between Autonomous Systems. At the host level, however, most likely you need only a static routing table. This is a table of routes that the OS kernel keeps. It is possible to add to and delete from routes in the kernel routing table relatively easily. We discuss routing tables based on RIP (RFC2453). When looking at routing tables, remember that most Unix-like operating systems use mnemonic names for their interfaces. For example, in Linux, the Ethernet interfaces on a machine are called eth0, eth1, eth2, etc. On the newer SUN/Solaris machines the interfaces are named eri0, eri1, etc. PPP interfaces are usually names ppp0, ppp1 etc. You can see all the configured interfaces on a host using the ifconfig command which is usually found in /sbin/ directory (but not always). You can see the routing table with ªnetstat -rº command. Here©s a screen shot of these commands run on matrix.newpaltz.edu which is a SUN/Solaris machine: The output from /sbin/ifconfig command shows that there are two configured interfaces, one an Ethernet and the other the loopback interface.
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