# Definition Statements

Definition statements are general configuration statements that relate to all of GateD or at least to more than one protocol. The three definition statements are `autonomoussystem`, `routerid` and `martians`. if used, `autonomoussystem`, `routerid` and `martians` must appear before any other type of configuration statement in gated.conf file.

## Autonomous System configuration

        autonomoussystem autonomous_system [ loops number ] ;

Sets the autonomous system number of this router to be `autonomous system`. This option is required if BGP or EGP are in use. The AS number is assigned by the Network Information Center (NIC).

`Loops` is only for protocols supporting AS paths, such as BGP. It controls the number of times this autonomous system may appear in an AS path and defaults to 1 (one).

## Router ID configuration

        routerid host ;

Sets the router identifier for use by the BGP and OSPF protocols. The default is the address of the first interface encountered by GateD. The address of a non-point-to-point interface is preferred over the local address of a point-to-point interface and an address on a loopback interface that is not the loopback address (127.0.0.1) is most preferred.

## Martian configuration

        martians {
            host host [ allow ] ;
    	network [ allow ] ;
    	network mask mask [ allow ] ;
    	network masklen number [ allow ] ;
            default [ allow ] ;
        } ;

Defines a list of martian addresses about which all routing information is ignored. Sometimes a misconfigured system sends out obviously invalid destination addresses. These invalid addresses, called martians, are rejected by the routing software. This command allows additions to the list of martian addresses. See the section on Route Filtering for more information on specifying ranges. Also, the `allow` parameter may be specified to explicitly allow a subset of a range that was disallowed.

## Sample Definition Statements

        options gendefault ;
        autonomoussystem 249 ;
        interface 128.66.12.2 passive ;
        martians {
            0.0.0.26
        };

The statements in the sample perform the following functions:

- The options statement tells the system to generate a default route when it peers with an EGP or BGP neighbor.
- The autonomoussystem statement tells GateD to use AS number 249 for in EGP and BGP.
- The interface statement tells GateD not to mark interface 128.66.12.2 as down even if it sees no traffic.
- The martians statement prevents routes to 0.0.0.26 from ever being accepted.

Last updated 1994/03/16 21:38:12.