Default route Once you have completed the "basic host information" form, your _L_i_n_u_x system knows how to send packets to other TCP/IP machines on your net- work. That's it. If you try to send packets to a host (another com- puter) on a different Ethernet network, it won't work unless you tell the system which gateway to use to reach the other network. 11.. BBaassiicc ttooppoollooggyy ooff aa LLAANN ((LLooccaall AArreeaa NNeettwwoorrkk)).. A LAN is generally a set of machines sharing a common Ethernet network. Quite often, several separate LANs are connected together using one or more routers. One simple and effective router is a _L_i_n_u_x system with two Ethernet adapters. If there is only one gateway connecting your LAN to other LANs or even the _I_n_t_e_r_n_e_t, setting the default route to the IP address of this gateway is a safe bet. 22.. WWhheenn nnoott ttoo uussee aa ddeeffaauulltt rroouuttee If your system is connected to the _I_n_t_e_r_n_e_t using either SLIP or PPP, then don't set the default route in _L_i_n_u_x_c_o_n_f. Just select the default route option of the specific connectivity package you are using (dip, pppd, slirp). Those packages will setup the default route when the link is up and remove it when it goes down. With PPP, IP numbers are often allocated dynamically from the other side, so you have little idea of the gateway IP until the link is up. On complex networks with many LANs, with many gateways and even redundant gateways, your best bet is to use dynamic routing with packages like routed (supported by _L_i_n_u_x_c_o_n_f) or gated. 33.. TThhee ddeeffaauulltt rroouuttee iiss cchheecckkeedd llaasstt aannyywwaayy The default route is always the last one checked by the kernel. The command "netstat -nr" shows this. So you may set the default route and then add routes to specific networks or hosts later. These will take precedence over the default route.