ccna network plus

ccna network plus.AS_PATH: The sequence of autonomous systems through which the routing information contained in the Update passes. Next_HOP: The next hop of the BGP route obtained by the router. For an EBGP session, the next hop is the source address of the neighboring router that advertised the route. For an IBGP session, there are 2 cases, one is that the next hop of the route originating within the AS is the source address of the neighboring router that advertised the route, and the other is that the route injected into the AS by EBGP has its next hop unchanged and carried into IBGP. (2) Well-KnownDiscretionary Recognized self-determination refers to attributes that must be recognized by all BGP devices, but may or may not be sent during the BGP update process, including the attributes LOCAL_PREF and ATOMIC_ AGGREGATE. LOCAL_PREF (local priority): used to tell routers within an autonomous system how to leave the autonomous system when there are multiple paths. The higher the local priority, the higher the route priority. This attribute is only passed between IBGP neighbors. ATOMIC.AGGREGATE (Atomic Aggregation): indicates that information that has been lost When routes are aggregated this will cause information to be lost because the aggregation may come from different sources with different attributes. If a router sends an aggregation that causes information to be lost, the router is required to append the atomic aggregation attribute to that route. (3) OptionalTransitive The optional transition attribute is not required to be supported by all BGP implementations. If the attribute is not recognized by the BGP process, it looks at the transition flag. If the transition flag is set, the BGP process accepts the attribute and transmits it unchanged, including AGGREGATOR and COMMUNITYo AGGREGATOR: Identifies the BGP router ID that implements the route aggregation and the AS number of the router that aggregates the route. COMMUNITY: refers to a group of routers that share a common attribute. (4) OptionalNontransitiveThe OptionalNontransitive attribute is not required to be supported by all BGPs. If these attributes are sent to a router that does not recognize them, they are discarded and cannot be transmitted to BGP neighbors, including MED, ORJGINATOR_ID, and CLUSTER_LISToMED (Multiple Exit Distinction): informs routers outside the AS which path to use to reach the AS. it is also considered an external metric for routing. a low MED value indicates a high priority. MED attributes are exchanged between autonomous systems. but MED attributes cannot be passed to third-party ASes. by default. routers compare their MED attributes only when the paths come from different neighbors of the same autonomous system.ORIGINATOR_ID (origin ID): the route reflector is attached to this attribute, which carries the source route of this ASThis attribute shows the router IDs of the servers, which are used to prevent loops. CLUSTER_LIST: This attribute shows the reflected paths used.Chapter 19 Branching Connections.361 .19.4.4BGP packet format1. BGP packet headersThe BGP packet types mainly include Open^ Keepalive>Update and Notification, which have the same packet header with a length of 19 bytes. The BGP packet header format is shown in Figure 19-7, and the meanings of the fields are described below.