7.7.1.1. A host configuration

# 
#  enable rip, don't broadcast updates, 
#  listen for RIP-2 updates on the multicast address, 
#  check that the updates are authentic. 
# 
rip yes { 
        nobroadcast ; 
        interface 172.16.9.23 
             version 2  
             multicast  
             authentication simple "REAL stuff" ; 
 } ;

The keyword nobroadcast prevents the host from broadcasting its own RIP updates. The default is nobroadcast when the system has one network interface, and broadcast when it has more than one. The nobroadcast keyword performs the same function as the -q command-line option does for routed. However, gated can do much more than routed, as the next clause shows.

The interface clause defines interface parameters for RIP. The parameters associated with this clause say that RIP-2 updates will be received via the RIP-2 multicast address on interface 172.16.9.23 and that authentic updates will contain the password REAL^stuff. For RIP-2, simple authentication is a clear-text password up to 16 bytes long. This is not intended to protect the system from malicious actions; it is intended only to protect the routers from a configuration accident. If a user mistakenly sets his system up as a RIP supplier, he is very unlikely to accidentally enter the correct password into his configuration. Stronger authentication is available in the form of a essage Digest 5 (MD5) cryptographic checksum by specifying md5 in the authentication clause.

7.7.1.2. Interior gateway configurations

#  Don't time-out subnet 9 
interfaces { 
    interface 172.16.9.1 passive ; 
} ; 
# Define the OSPF router id 
routerid 172.16.1.9 ; 
# Enable RIP-2; announce OSPF routes to 
# subnet 9 with a cost of 5. 
rip yes { 
    broadcast ; 
    defaultmetric 5 ; 
    interface 172.16.9.1 
         version 2 
         multicast 
         authentication simple "REAL stuff" ; 
} ; 
# Enable OSPF; subnet 1 is the backbone area; 
# use password authentication. 
ospf yes { 
     backbone { 
          interface 172.16.1.9 { 
              priority 5 ; 
              auth simple "It'sREAL" ; 
              } ; 
          } ;
} ;

The interfaces statement defines routing characteristics for the network interfaces. The keyword passive in the interface clause is used here, just as we have seen it used before, to create a permanent static route that will not be removed from the routing table. In this case, the permanent route is through a directly attached network interface. Normally when gated thinks an interface is malfunctioning, it increases the cost of the interface by giving it a high-cost preference value (120) to reduce the probability of a gateway routing data through a non-operational interface. gated determines that an interface is malfunctioning when it does not receive routing updates on that interface. We don't want gated to downgrade the 172.16.9.1 interface, even if it does think the interface is malfunctioning, because our router is the only path to subnet 9. That's why this configuration includes the clause interface 172.16.9.1 passive.

The routerid statement defines the router identifier for OSPF. Unless it is explicitly defined in the configuration file, gated uses the address of the first interface it encounters as the default router identifier address. Here we specify the address of the interface that actually speaks OSPF as the OSPF router identifier.

The ospf yes statement enables OSPF. The first clause associated with this statement is backbone. It states that the router is part of the OSPF backbone area. Every ospf yes statement must have at least one associated area clause. It can define a specific area, e.g., area 2, but at least one router must be in the backbone area. While the OSPF backbone is area 0, it cannot be specified as area 0; it must be specified with the keyword backbone. In our sample configuration, subnet 1 is the backbone, and all routers attached to it are in the backbone area. It is possible for a single router to attach to multiple areas with a different set of configuration parameters for each area. Notice how the nested curly braces group the clauses together. The remaining clauses in the configuration file are directly associated with the backbone area clause.

The interface that connects this router to the backbone area is defined by the interface clause. It has two associated subclauses, the priority clause and the auth clause.

The priority 5 ; clause defines the priority used by this router when the backbone is electing a designated router. The higher the priority number, the less likely a router will be elected as the designated router. Use priority to steer the election toward the most capable routers.

7.7.1.3. Exterior gateway configuration

# Defines our AS number for BGP 
autonomoussystem 249; 
 
# Defines the OSPF router id 
routerid 172.16.1.1; 
 
# Disable RIP 
rip no; 
 
# Enable BGP 
bgp yes { 
   group type external peeras 164 { 
        peer 10.6.0.103 ; 
        peer 10.20.0.72 ; 
        }; 
}; 
 
# Enable OSPF; subnet 1 is the backbone area; 
# use password authentication. 
ospf yes { 
     backbone { 
         interface 172.16.1.1 { 
              priority 10 ; 
              auth simple "It'sREAL" ; 
              } ; 
          } ; 
}; 
 
# Announce routes learned from OSPF and route 
# to directly connected network via BGP to AS 164 
export proto bgp as 164 { 
     proto direct ; 
     proto ospf ; 
}; 
 
# Announce routes learned via BGP from  
# AS number 164 to our OSPF area. 
export proto ospfase type 2  { 
     proto bgp autonomoussystem 164  { 
          all ;    
          };
};

7.7.2.1. Running gated at startup

Our imaginary gateway, crab, is a Solaris system with code in the /etc/init.d/inetinit file that starts routed. We comment out those lines, and add these lines:

if [ -f /usr/sbin/gated -a -f /etc/gated.conf ]; then 
     /usr/sbin/gated;      echo -n 'gated' > /dev/console
fi

This code assumes that gated is installed in /usr/sbin and that the configuration file is named /etc/gated.conf. The code checks that gated is present and that the configuration file /etc/gated.conf exists. If both files are found, gated begins.

The code checks for a configuration file because gated usually runs with one. If gated is started without a configuration file, it checks the routing table for a default route. If it doesn't find one, it starts RIP; otherwise, it just uses the default route. Create an /etc/gated.conf file even if you only want to run RIP. The configuration file documents your routing configuration and protects you if the default configuration of gated changes in the future.