| Chapter Syllabus 16.1 The gated.conf Configuration File 16.2 Router Discovery Protocol (RDP) 16.3 Routing Information Protocol (RIP) 16.4 Open Shortest Path First (OSPF) In Chapter 15, we discussed the use of static routes as one way to enable nodes to communicate with each other when they are connected to physically and logically separate networks. We discussed that, even though a router may fail, a static route behaves as its name suggests ” statically . Even if there were an alternative router on the network, we would have to manually manage static routes with the route command. In a large, complex, highly available network configuration, we can't rely on an administrator sitting at his desk watching the state of every network link just in case one fails. This is the job of the dynamic routing daemon gated . The gated can provide dynamic routing and automatic rerouting in the event that a particular route fails. This is crucial in a High Availability environment where we may have multiple physical network links to our servers, our client machines, and our customers. It is the job of the gated to maintain the kernel routing table. We should stress at this point that we should use either static routes (the route command) or dynamic route (the gated daemon), but don't use both because the results are ill-defined. The other aspect of gated that makes it a good choice for maintaining our kernel routing table is the fact that it supports numerous routing protocols. This allows an HP-UX hosts running gated to communicate with many other hosts and commercial routers using specific protocols. To illustrate some capabilities of the gated , we use the simple network configuration we saw in Chapter 15: Figure 16-1. Network for dynamic routing. 
The only physical difference is that I will maintain my APA configuration established at the end of Chapter 15, on node hpeos003 . There are essentially three solutions that our nodes can employ to discover all the available routers in our network: -
Listen for ICMP router advertisements from the Router Discover Protocol. -
Use a vector-distance routing protocol such as RIP, RIP-II. -
Use a link-state routing protocol such as OSPF. All these solutions are handled by the gated dynamic routing daemon. The first solution used to be handled by a separate daemon called rdpd , which is now obsolete because the functionality has been subsumed into gated . | 