reserved for private use are 64512 to 65534. The two redistribute clauses define the routes that will be advertised to our BGP neighbors. redistribute connected tells the router to advertise routes for all networks to which the router is directly connected. redistribute ospf tells the router to advertise routes that it learns from OSPF. The neighbor clauses define the two BGP neighbors that this router should peer with. The neighbors are defined by an IP address, and the external autonomous system to which they belong is identified by the remote-as parameter. In Listing 7.14, the external ASN is 164. Do not use this number or 249. They are both officially assigned to government networks. Zebra is beta software that has only recently begun shipping with Linux distributions, and it is not the only choice for routing software. Many systems still use gated, which is our next topic. Using gated Despite the fact that Red Hat Linux uses Zebra as its default routing software, many other Linux distributions ship with gated. If you don’t have gated software with your distribution, a commercial version can be obtained from the Internet at http://www.gated.org/. Also, at this writing, you can still find and download a precompiled Linux gated binary from an online repository. However, if your distribution doesn’t include gated, this is a good time to transition to Zebra. If you do have gated, and you want to use it, read on. Like Zebra, gated supports many of the most advanced routing protocols. Unlike Zebra, the free version of gated combines these protocols in a single large program. gated was created to allow a system to run multiple routing protocols and to combine the routes learned from those protocols. It does this using a preference value. A gated preference value is an arbitrary number between 0 and 255 that indicates whether one source of routing information is preferred over another. The sources of information can be different routing protocols, different interfaces, different routers, and different routing domains. The lower the preference number, the more preferred the source. The default preferences used for routing protocols are shown in Table 7.1. Table 7.1: Default gated Preference Values Route Source Preference Value Direct route 0 OSPF 10 IS-IS Level 1 15 IS-IS Level 2 18 Internally generated default 20 ICMP redirect 30 Routes learn from the route socket 40 Static route 60 SLSP routes 70 HELLO routes 90 RIP 100 Point-to-Point interface routes 110 Routes through a downed interface 120 Aggregate and generate routes 130 218

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