Configuring Internet Protocol (IP) routing

gated EGP protocol statement

   egp yes|no|on|off [ {
       [preference preference ;]
       [defaultmetric metric ;]
       [packetsize maxpacketsize ;]
       [traceoptions traceoptions ;]
       [group      [peeras autonomous_system]
               [localas autonomous_system]
               [maxup number]
               [preference preference]
       {
           neighbor host
               [metricout metric]
               [nogendefault]
               [importdefault]
               [exportdefault]
               [gateway gateway]
               [lcladdr local_address]
               [sourcenet network]
               [ { minhello | p1 } min_hello]
               [ { minpoll | p2 } min_poll]
               [traceoptions traceoptions] {
               ;
           . . .
        } ;
       . . .]
   } ] ;

preference preference

Sets the preference for routes learned from RIP. The default preference is 200. This preference may be overridden by a preference specified on the group or neighbor statements or by import policy.

defaultmetric metric

Defines the metric used when advertising routes via EGP. If not specified, the default value is 255, which some systems may consider unreachable. This choice of values requires you to explicitly specify a metric when exporting routes to EGP neighbors. This metric may be overridden by a metric specified in the neighbor or group statements or in export policy.

packetsize maxpacketsize

Defines the expected maximum size of a packet that EGP expects to receive from this neighbor. If a packet larger than this value is received, it will be incomplete and have to be discarded. The length of this packet will be noted and the expected size will be increased to be able to receive a packet of this size. Specifying the parameter here will prevent the first packet from being dropped. If not specified, the default size is 8192 bytes. All packet sizes are rounded up to a multiple of the system page size.

traceoptions traceoptions

Specifies the tracing options for EGP. By default, these are inherited from the global trace options. These values may be overridden on a group or neighbor basis. (See ``gated trace statements'').

group

EGP neighbors must be specified as members of a group. A group is usually used to group all neighbors in one autonomous system. Parameters specified in the group clause apply to all of the subsidiary neighbors unless explicitly overridden in a neighbor clause. Any number of group clauses may specify any number of neighbor clauses.

Any parameters from the neighbor subclause may be specified on the group clause to provide defaults for the whole group (which may be overridden for individual neighbors). In addition, the group clause is the only place to set the following attributes:

peeras: Identifies the autonomous system number expected from peers in the group. If not specified, it will be learned dynamically.
localas: Identifies the autonomous system that gated is representing to the group. The default is that which has been set globally in the autonomoussystem statement. This option is usually only used when masquerading as another autonomous system and its use is discouraged.
maxup: Specifies the number of neighbors gated should acquire from this group. The default is to acquire all of the neighbors in the group. gated will attempt to acquire the first maxup neighbors in the order listed. If one of the first neighbors is not available, it will acquire one further down the list. If after startup gated does manage to acquire the more desirable neighbor, it will drop the less desirable one.
preference preference: Specifies the preference used for routes learned from these neighbors. This can differ from the default EGP preference set in the egp statement, so that gated can prefer routes from one group of neighbors over another. This preference may be explicitly overridden by import policy.

neighbor host

Each neighbor subclause defines one EGP neighbor within a group. The only part of the subclause that is required is the neighbor_address argument, which is the symbolic host name or IP address of the neighbor. All other parameters are optional.

metricout metric

This defines a metric to be used for all routes sent to this neighbor. The value overrides the default metric set in the egp statement and any metrics specified by export policy, but only for this specific neighbor or group of neighbors.

nogendefault

Prevents gated from generating a default route when EGP receives a valid update from its neighbor. The default route is only generated when the gendefault option is enabled.

importdefault

Enables gated to accept the default route (0.0.0.0) if it is included in a received EGP update. If not specified, the default route contained in an EGP update is ignored. For efficiency, some networks have external routers announce a default route to avoid sending large EGP update packets.

exportdefault

Enables gated to include the default route (0.0.0.0) in EGP updates sent to this EGP neighbor. This allows the system to advertise the default route via EGP. Normally, a default route is not included in EGP updates.

gateway gateway

If a network is not shared with a neighbor, gateway specifies a router on an attached network to be used as the next hop router for routes received from this neighbor. This option is only rarely used.

lcladdr local_address

Specifies the address to be used on the local end of the connection with the neighbor. The local address must be on an interface that is shared with the neighbor or with the neighbor's gateway when the gateway parameter is used. A session will only be opened when an interface with the appropriate local address (through which the neighbor or gateway address is directly reachable) is operating.

sourcenet network

Specifies the network queried in the EGP Poll packets. By default, this is the network shared with the neighbors address specified. If there is no network shared with the neighbor, one of the networks the neighbor is attached to should be specified. This parameter can also be used to specify a network shared with the neighbor other than the one on which the EGP packets are sent. This parameter is normally not needed.

p1 time
minhello time

Sets the minimum acceptable interval between the transmission of EGP Hello packets. The default Hello interval is 30 seconds. If the neighbor fails to respond to three Hello packets, gated stops trying to acquire the neighbor. Setting a larger interval gives the neighbor a better chance to respond. The keyword minhello is an alias for the P1 value defined in the EGP specification.

p2 time
minpoll time

Sets the time interval between polls to the neighbor. The default is 120 seconds. If three polls are sent without a response, the neighbor is declared "down" and all routes learned from that neighbor are removed from the routing database. A longer polling interval supports a more stable routing database but is not as responsive to routing changes. The keyword minpoll is an alias for the P2 value defined in the EGP specification.

traceoptions traceoptions

Specifies the tracing options for this EGP neighbor. By default these are inherited from group or EGP global trace options. (See ``gated trace statements'').