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Chapter 10These daemons update the kernel's routing table based on the routes they learn fromthe updates they receive from other routing daemons over the network.In fact, the routing daemon keeps its own routing table,which may contain differentdestinations for a subnet. But it installs only the best route for each destination,calculated using the distance vector algorithm.You may not want to use RIPv1 in your network, because it is not aclassless protocol and hence does not respect the subnet mask, andassumes the obsolete concept of "classes" instead of subnets. Newgenerations of the protocol (that is RIPv2) have solved this issue bytransmitting subnet masks in routing update messages. Due to this fact,RIPv1 is not covered in this chapter. However, the routed(8) manualpages contain useful information, in case you are interested in runningRIPv1, using routed on your network.To enable the routing daemon, you should modify your /etc/rc.conf file:router_enable="YES"ipv6_router_enable="YES"The above lines enable routed and route6d respectively. You can also manually runthe routing daemons by running the following rc scripts:# /etc/rc.d/routed start# /etc/rc.d/route6d startOnce the routed daemon is launched, it looks for all available (up and running)interfaces, creates appropriate routing entries in the kernel's routing table andremoves all non-static routes from it. After that, the routing daemon starts sendingrouting updates to all active interfaces, every thirty seconds.When only one active interface is present (or when -q parameter is passed torouted), it does not transmit any routing information on the interface, and onlylistens for incoming routing advertisements.Running OSPF—OpenOSPFDOpenOSPFD is an open-source implementation of the IETF standard OpenShortest-Path First (OSPF) protocol, a widely used link-state IGP protocol. OSPFprotocol uses Dijkstra's algorithm to find the shortest path between two hosts.Unlike many other protocols, OSPF does not rely on TCP or UDP to talk to otherrouters. Instead, it encapsulates its messages directly on top of the IP (protocol 89).[ 163 ]