HP OpenVMS Systems Documentation

Every protocol has one or more options for tracing packets. All protocols allow the packets keyword to be used for tracing all packets sent and received by the protocol. Most protocols have other options for limiting tracing to a useful subset of packet types. These tracing options can be further controlled with the following modifiers:

Directive statements provide direction to the GATED configuration language parser about included files and the directories in which these files reside. Directive statements are immediately acted upon by the parser. Other statements terminate with a semicolon (;), but directive statements terminate with a new line. The two directive statements are as follows:

• %directory directory
  Defines the directory in which the include files are stored. When it is used, GATED searches the directory identified by path name for any included files that do not have a fully qualified file name (do not begin with "/"). This statement does not change the current directory; it only specifies the prefix applied to included file names.
• %include filename
  Identifies an include file. The contents of the file is included in the TCPIP$GATED.CONF file at the point where the %include directive is located. If the file name is not fully qualified (does not begin with backslash (/), it is considered to be relative to the directory defined in the %directory directive. The %include directive statement causes the specified file to be parsed completely before resuming with this file. Nesting up to ten levels is supported. The maximum nesting level can be increased by changing the definition of FI_MAX in the parse.h file.

In a complex environment, segmenting a large configuration into smaller, more easily understood segments might be helpful, but one of the advantages of GATED is that it combines the configuration of several different routing protocols into a single file. Segmenting a small file unnecessarily complicates routing configurations.

A.9 Options Statements

The options statement allows specification of some global options. If used, options must appear before any other type of configuration statement in the TCPIP$GATED.CONF file.

The syntax for the options statement is as follows:

  options
 [nosend]
 [noresolv]
 [gendefault [preference preference] [gateway gateway]]
 [mark time]
 ;

The options list can contain one or more of the following options:

An interface is the connection between a router and one of its attached networks. A physical interface can be specified by interface name, by IP address, or by domain name (unless the network is an unnumbered point-to-point network). Multiple levels of reference in the configuration language allow identification of interfaces using a wildcard or interface type name. Be careful with the use of interface names because future versions of TCP/IP Services may allow more than one address per interface. The interface_list is a list of one or more interface names including wildcard names (names without a number) and names that may specify more than one interface or address, or the token all for all interfaces.

The syntax for the interfaces statement is as follows:

  interfaces {
       options
            [strictinterfaces]
            [scaninterval time]
            [aliases-nexthop ( primary | lowestip | keepall )
            ;
       interface interface_list
            [preference preference]
            [down preference preference]
            [passive]
            [simplex]
            [reject]
            [blackhole]
            [ AS autonomoussystem ]
            ;
       define  address
            [broadcast address] | [pointtopoint  address]
            [netmask mask]
            [multicast]
            ;
          } ;

The options portion of the interfaces statement allows configuration of the following global options related to interfaces:

The interface portion of the interfaces statement sets interface options on the specified interfaces. An interface list is all or a list of interface names (see Section A.10.1), domain names, or numeric addresses. Options available on this statement are:

The define portion of the interfaces statement defines interfaces that might not be present when GATED is started so they may be referenced in the configuration file when strictinterfaces is defined. The following are valid define keywords:

An interface list is a list of references to interfaces or groups of interfaces. The following four methods, from most general to most specific, are available for referring to interfaces:

If many interface lists are present in the TCPIP$GATED.CONF file with more than one parameter, these parameters are collected at run time to create the specific parameter list for a given interface. If the same parameter is specified on more than one list, the parameters with the most specific interface are used.

For example, the following interface list is for a system with three interfaces, LE0, LE1, and DU0:

       rip yes {
           interface all noripin noripout ;
           interface le ripin ;
           interface le1 ripout ;
       } ;

In this example, RIP packets are accepted from interfaces LE0 and LE1, but nor from DU0. RIP packets are sent only on interface LE1.

A.10.1.1 Example of Current Define Statements for GATED

interfaces {
   define 192.168.12.5 broadcast 192.168.12.255 netmask 255.255.255.0 ;
   define 192.168.13.129 netmask 255.255.255.252 broadcast 192.168.13.131;

   # pointtopoint - is local side, 1st address is remote
   define  192.168.13.116 pointtopoint 192.168.13.114 multicast;
   };

• The first define statement has an Ethernet where you need to define the broadcast address as a /24.
• The second define statement shows how a /30 may be implemented in the define statement. The define tells GATED to treat the interface with a local address of 192.168.13.129, a netmask of 255.255.255.252, and a broadcast address of 192.168.13.131.
• The third define statement shows how a point-to-point interface is defined. The remote side of the point-to-point interface is specified first, and the local side (the one on this machine) is specified second.

The BSD 4.3 and later networking implementations allow the following four types of interfaces. Some implementations allow multiple protocol addresses per physical interface, but these are mostly based on BSD 4.3 RENO or later.

The GATED daemon ensures that there is a route available to each IP interface that is configured and up. Normally this is done by the SET INTERFACE command that configures the interface; GATED also does it to ensure consistency.

For point-to-point interfaces, GATED installs some special routes. GATED installs a route to the local address pointing at the loopback interface with a preference of 110. This ensures that packets originating on this host destined for this local address are handled locally.

OSPF prefers to route packets for the local interface across the point-to-point link where they will be returned by the router on the remote end. This is used to verify operation of the link. Because OSPF installs routes with a preference of 10, these routes override the route installed with a preference of 110.

When the status of an interface changes, GATED notifies all the protocols, which take the appropriate action. The GATED daemon assumes that interfaces that are not marked UP do not exist.

The GATED daemon ignores any interfaces that have invalid data for the local, remote, or broadcast addresses or the subnet mask. Invalid data includes zeros in any field. The GATED daemon also ignores any point-to-point interface that has the same local and remote addresses; it assumes it is in some sort of loopback test mode.

A.11 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 TCPIP$GATED.CONF file.

A.11.1 Autonomous System Configuration

The statement autonomoussystem as_number [loops number]; sets the AS number of this router used by BGP EGP. The AS number is the official autonomous system number assigned to you by the Network Information Center (NIC).

The loops parameter 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).

A.11.2 Router ID Configuration

The statement 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.

A.11.3 Martian Configuration

Sometimes a misconfigured system sends out invalid destination addresses. These invalid addresses, called martians, are rejected by the routing software. A martian configuration defines a list of martian addresses from which all routing information is ignored. A martian configuration is structured as follows:

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

The martians martian_list statement adds martian addresses to a martian address list. Routing information will not be accepted from the addresses specified in this list.

You can specify the allow parameter to explicitly allow a subset of a range that was disallowed.