gated.conf File Format for TCP/IP

Purpose

Contains configuration information for the gated daemon.

Description

The /etc/gated.conf file contains configuration information for the gated daemon. The file contains a sequence of statements. Statements are composed of tokens separated by white space. You can create white space using any combination of blanks, tabs, and new lines. The gated.conf file supports eight classes of statements:

You terminate a statement with a ; (semi-colon), except for directive statements. You terminate directive statements with a newline character.

You can specify directive and trace statements in any order in the gated.conf file. The remaining classes must be specified in order: trace, option, interface, definition, protocol, static route, and control.

You can specify comments in the gated.conf file using a # (pound sign) or C programing comments. To create a comment with a # pound sign, place the pound sign at the beginning of the line and the system ignores everything to the end of the line. C comments can appear anywhere on a line. A C comment starts with an /* (slash asterisk) and continues until it ends with */ (asterisk slash).

Statement Primitives

Statements are constructed using a number of primitives. These primitives are the following:

Directive Statements

Directive statements specify include files and the directories they reside in. Directive statements end with a newline. The following are directive statements:

Trace Statements

The following trace statements control tracing options and specify trace-output level:

Options Statements

Option statements specify global options. An option statement has the following form:

options OptionList

The OptionsList parameter sets gated daemon options. The following are valid options:

Interface Statements

Interface statements specify interface options. Interface statements have the following form:

interface {
          options [ strictifs ] [ scaninterval Time 
];
          interface InterfaceList InterfaceOptions;
          define Address [ broadcast Address | 
pointopoint 
              LocalAddress ]
                              [ netmask Netmask ] [ multicast ];
};

The interface statement clauses have the following values:

Definition Statements

The following definition statements specify options, the autonomous system, martian networks, and interface options:

Protocol Statements

This section explains the configuration options for routing protocols. These options enable or disable the use of a protocol and control protocol options. Protocol statements may be specified in any order. The protocol statements consist of one of the following protocol names:

• rip
• hello
• egp
• bgp
• redirect
• snmp

For all protocols, preference controls the choice of routes learned with this protocol or from this autonomous system in relation to routes learned from other protocols or autonomous systems. The default metric used when propagating routes learned from other protocols is specified with defaultmetric which itself defaults to the highest valid metric. For many protocols, this signifies a lack of reachability.

For distance vector IGPs with no explicit connections or authentication (RIP and HELLO) and redirects (ICMP), the trustedgateways clause supplies a list of gateways providing valid routing information. Routing packets from other gateways are ignored. This defaults to all gateways on the attached networks.

Routing packets can be sent not only to the remote end of point-to-point links and the broadcast address of broadcast-capable interfaces, but also to specific gateways if they are listed in the sourgateways clause and yes or on is specified. If nobroadcast is specified, routing updates are sent only to gateways listed in the sourcegateways clause and not at all to the broadcast address. You can disable the transmission and reception of routing packets for a particular protocol with the interface clause. An interface clause that disables sending or receiving protocol packets can be overridden for specific peers using the trustedgateways and sourcegateways clauses.

For exterior protocols, (BGP, EGP), the autonomous system advertised to the peer is specified by the global autonomoussystem clause unless it is also overridden by the asout option. The incoming autonomous system number is not verified unless peeras is specified. Specifying metricout fixes the outgoing metric for all routes propagated to this peer. If the peer does not share a network, you can use interface to specify the interface address to use when communicating with this peer. Use gateway to specify the next hop to use for all routes learned from this peer. An internal default is generated when routing information is learned from a peer unless you specify the nogendefault option.

Any protocol can have a traceoptions clause. This clause enables tracing for a particular protocol, group, or peer. The following protocol-specific options are:

• all
• general
• internal
• external
• route
• update
• task
• timer
• protocol
• kernel

Using the gated Daemon with the Routing Information Protocol (RIP)

The following protocol statement configures the (RIP) for the gated daemon:

If you do not specify the rip clause, the default is rip on. The nobroadcast option specifies that RIP packets are sent to gateways listed in the sourcegateways clause, if there are any. If you specify yes or on, RIP assumes nobroadcast if there is only one interface and broadcast if there is more than one. The broadcast option specifies that RIP packets are always generated. The nocheckzero option specifies that RIP should not ensure that the reserved fields in RIP packets are zero.

Note: Using the broadcast option with only one interface is useful only when propagating static routes or routes learned from another protocol. This will cause data packets to travel across the same network twice. This behavior may be tolerable in certain configurations.

If the version is specified as or defaults to 1, RIP version 2 packets are never sent except in response to a v2 POLL packet. If the version is specifies as 2, RIP version 2 packets are sent to the RIP multicast address if possible, or the broadcast address, unless the method is explicitly specified.

The default Metric is 16. The default Preference is 100.

Using the gated Daemon with the HELLO Protocol

The following protocol statement configures the Defense Communications Network Local-Network Protocol (HELLO) for the gated daemon:

If you specify the yes or on option, HELLO assumes nobrodcast if there is only one interface and broadcast if there is more than one. If the HELLO clause is not specified, the default is hello off. The broadcast option specifies that HELLO will be generated. The nobroadcast option specifies that HELLO packets be sent to gateways listed in the sourcegateways clause, if there are any.

Note: Using the broadcast option with only one interface is useful only when propagating static routes or routes learned from another protocol. This causes data packets to travel across the same network twice.

The default metricount option is 0. The default metricin option is a translation of the kernel interface metric into a hello metric plus 100 ( the default HELLO hop count).

The default Metric is 30000. The default Preference is 90.

Using the gated Daemon with the OSPF Protocol

These clauses have the following values:

OSPF inter and intra area are always imported into the gated routing table with a preference of 10. It is a violation of the protocol to do otherwise so it is not possible to override this. OSPF Autonomous System External (ASE) routes are imported with a preference of 150. This default can be changed with the preference keyword in the defaults section. ASE routes are imported at a rate of 100 ASEs every 1 second, you can tune these parameters with the exportlimit and exportinterval parameters.

gated routes are exported to OSPF as ASEs with a default cost of 0 and a type of 1. By default, the tag is calculated from the AS path of the route being exported (TAG AS). You can change all of these in the defaults section.

Notes:

1. You can specify OSPF areas in any order, but you must specify the backbone area last.
2. Reconfiguration (SIGHUP) is disabled when OSPF is enabled.

Using the gated Daemon with the Exterior Gateway Protocol (EGP)

The following protocol statement configures the EGP for the gated daemon:

These clauses have the following values:

The LocalAddress is used to set the address to a local address that is used when there is a choice of interfaces. If you do not specify the local address, it defaults to which ever interface is shared with the neighbor. If a network is not shared with the neighbor, use the gateway clause to specify the next-hop gateway to use when installing routes learned from this neighbor. In this case, the default interface is the one shared with the specified gateway.

The default metric is 255. The default preference is 200.

Using the gated Daemon with the Border Gateway Protocol (BGP)

The following protocol statement configures the BGP for the gated daemon:

The BGP peers are assigned to groups based on the type and peeras options. It is not possible to have two groups with the same type and peeras. Peer specifies the address of each BGP peer. Group provides the default for all peers within that group.

The peeras option is the autonomous system expected from a peer. The metricout option is the default metric used when sending to a peer. The localas clause specifies the autonomous system advertised to this peer. The default is the system that was set globally. The nogendefault option specifies that this peer should not cause the automatic default to be generated.

The LocalAddress specifies the address to use on the local end of the TCP connection with the peer. For external peers, the local address must be on an interface that is shared with the peer (or for a non-local peer's configured next-hop gateway when the gateway option is used to specify this) and a session with the peer is opened only when an interface with the appropriate local address through which the peer (gateway) address is directly reachable is operating. For other types of peers, a peer session is maintained when any interface with the specified local address is operating. In either case, incoming connections are only recognized as matching a configured peer if they are addressed to the configured local address.

The remaining options have the following values:

You do not specify a metric option, the default is not to send a metric. The default preference option is 170.

Using the gated Daemon with the Internet Control Message Protocol (ICMP)

The following protocol statement controls how the gated daemon responds to ICMP redirects:

When functioning as a router ( that is, any interior routing protocols RIP, HELLO, OSPF are participating in routing any interface), ICMP redirects are disabled. When ICMP redirects are disabled, the gated daemon must actively remove the effects of redirects from the kernel as the kernel always processes ICMP redirects.

The default Preference parameter is 30.

Using the gated Daemon with the Simple Network Management Protocol (SNMP)

The following protocol statement specifies whether the gated daemon tries to contact the SNMP daemon to register supported variables.

The default snmp value is on. The default Preference parameter is 50. The default Port parameter is 199 (SMUX).

Static Statements

You can define any number of static statements. Each statement can contain any number of static route definitions. The first form defines a static route through one or more gateways. If you specify multiple gateways, they are limited by the number of multipath destinations supported, this is always 1. Only gateways on interfaces that are configured and up are used.

The second form defines a static interface route that is used for primitive support of multiple networks on one interface.

The interface list on the first form restricts static routes to a specific set of interfaces. The options in these forms have the following values:

The Preference option for static routes defaults to 60.

Control Statements

Import and export clauses control importation of routes from routing protocol peers and export of routes to routing protocol peers. These clauses have the following form:

If an OSPF type is specified, only routes of that type are considered for import. Otherwise, either import or export types are considered. if an OspfTag specification is given, only routes matching that tag specification are considered. Otherwise, any tag is considered. An OSPF tag specification is a decimal, hexidecimal or dotted quad number.

If you specify more than one import statement relevant to a protocol, they are processed most specific to least specified (that is, for RIP and HELLO, gateway, interface, and protocol), then in the order specified in the gated.conf file.

An ImportList consists of zero or more destinations (with optional mask). You can specify restrict to prevent a set of destinations from being imported or a specific preference for this set of destinations. The format of this set is as follows:

The contents of an import list are sorted internally so that entries with the most specific masks are examined first. The order in which the DestinationMask entries are specified does not matter.

If you do not specify an ImportList, all routes are accepted. If an import list is specified, the import list is scanned for a matching route. If no match is found, the route is discarded. An allrestrict entry is assumed in an import list.