Table 2: Immediate Subattributes of neighbor
Attribute Description
as The NHI prefix address of this neighbor's AS. In other words, the global id of the Net which is the AS boundary for this neighbor. If it is identical to the NHI prefix of the local BGP speaker's AS, then it is interpreted as an internal neighbor. Otherwise it is interpreted as an external neighbor. This is a required subattribute of neighbor. (When autoconfiguration is in use, a neighbor's AS will be identified automatically.)
address For an external neighbor, this must be an NHI interface address relative to the neighbor's AS. For an internal neighbor it must be an NHI host address relative to the local AS. This is a required subattribute of neighbor. (When autoconfiguration is in use, a neighbor's address will be set to the address of the physical interface on the end of the point-to-point link which connects it to the local router.)
use_return_address The NHI interface address, relative to the local AS, which the neighbor should use when sending messages to the local BGP speaker. Often an internal peer will use the address of a virtual (loopback) interface, while an external peer will typically use the address of a physical interface on a point-to-point link. This is a required subattribute of neighbor. (When autoconfiguration is in use, the return address used by a neighbor is the address of the physical interface on the local router which is on the end of the point-to-point link which connects the local router to this neighbor.)
hold_time The value, in seconds, to be used as the proposed length of the Hold Timer Interval during peering session establishment. The actual Hold Timer Interval, once determined, represents the maximum amount of time which can elapse between the receipt of any two successive messages (of type KeepAlive or Update) from a particular peer without loss of connectivity to that peer. This is a required subattribute of neighbor if no global default value has been explicitly configured. (When autoconfiguration is in use and no global default value has been configured, a neighbor will have an associated proposed Hold Timer Interval value of 90.)
keep_alive_time The value, in seconds, of the Keep Alive Timer Interval. It represents the maximum amount of time that should elapse between successive messages (of type KeepAlive or Update) which are sent to a peer. The value may be adjusted during peering session establishment when the Hold Timer Interval is negotiated, and also when jitter is applied. This is a required subattribute of neighbor if no global default value has been explicitly configured. (When autoconfiguration is in use and no global default value has been configured, a neighbor will have an associated Keep Alive Timer Interval value of 30.)
mrai The value, in seconds, of the Minimum Route Advertisement Interval (MRAI). It is the minimum amount of time which must elapse between successive advertisements of routes regarding the same destination which are sent to the same peer. The value may be adjusted when jitter is applied. This is a required subattribute of neighbor except when certain global default values have been explicitly configured. The MRAI for an internal neighbor need not be specified if a global default value for MRAI for internal connections has been configured. The MRAI for an external neighbor need not be specified if a global default value for MRAI for external connections has been configured. (When autoconfiguration is in use, a neighbor will have an associated Minimum Route Advertisement Interval value of 30, unless global default values have been configured as described above in the manual configuration case.)
ibgp This attribute is only meaningful if this is an internal neighbor and if the local BGP speaker is itself a route reflector. If that is the case, then the presence of this attribute indicates that this neighbor is in the same Internal BGP route reflection cluster as the local BGP speaker. The value of the attribute (either reflector or client) indicates whether the neighbor is a reflector or a client. The omission of this attribute for an internal neighbor of a route reflector indicates that it is not in a cluster with the local BGP speaker, and thus is a non-client. (When autoconfiguration is in use, route reflection is not used.)
infilter Encapsulates the filtering policy for inbound route advertisements from this neighbor. A filter may permit or deny routes based on their attributes (which include the routes' destination and their path attributes). Furthermore, a filter may arbitrarily modify the path attributes of permitted routes. This is a required subattribute of neighbor. See Table 3 for a description of its subattributes. (When autoconfiguration is in use, a policy which permits all routes, without modifying them, is used.) Note: Filtering features are still in the experimental stage. Use with care.
outfilter Encapsulates the filtering policy for outbound route advertisements to this neighbor. A filter may permit or deny routes based on their attributes (which include the routes' destination and their path attributes). Furthermore, a filter may arbitrarily modify the path attributes of permitted routes. This is a required subattribute of neighbor. See Table 3 for a description of its subattributes. (When autoconfiguration is in use, a policy which permits all routes, without modifying them, is used.) Note: filtering features are still in the experimental stage. Many aspects are as of yet unimplemented or untested. Use with care.