3Com S7906E Configuration Manual page 774

Optional non-transitive: If a BGP router does not support this attribute, it will not advertise routes
with this attribute.
The usage of each BGP path attribute is described in the following table.
Table 1-1 Usage of BGP path attributes
ORIGIN
AS_PATH
NEXT_HOP
LOCAL_PREF
ATOMIC_AGGREGATE
AGGREGATOR
COMMUNITY
MULTI_EXIT_DISC (MED)
ORIGINATOR_ID
CLUSTER_LIST
Usage of BGP path attributes
1) ORIGIN
ORIGIN is a well-known mandatory attribute, which defines the origin of routing information, that is, how
a route became a BGP route. It involves three types:
IGP: Has the highest priority. Routes added to the BGP routing table using the network command
have the IGP attribute.
EGP: Has the second highest priority. Routes obtained via EGP have the EGP attribute.
incomplete: Has the lowest priority. The source of routes with this attribute is unknown, which does
not mean such routes are unreachable. The routes redistributed from other routing protocols have
the incomplete attribute.
2) AS_PATH
AS_PATH is a well-known mandatory attribute. This attribute identifies the autonomous systems
through which routing information carried in this Update message has passed. When a route is
advertised from the local AS to another AS, each passed AS number is added into the AS_PATH
attribute, thus the receiver can determine ASs to route the massage back. The number of the AS
closest to the receiver's AS is leftmost, as shown below:
Name
Well-known mandatory
Well-known mandatory
Well-known mandatory
Well-known discretionary
Well-known discretionary
Optional transitive
Optional transitive
Optional non-transitive
Optional non-transitive
Optional non-transitive
1-5
Category