IP 101 ge-0/0/1.0 10.32.37.241 #show route advertising-protocol bgp 10.32.94.169 Prefix Nexthop MED Lclpref AS path * 10.32.37.0/24 Self 16777215 I * 10.32.37.0/26 Self 101 I * 10.32.37.64/26 Self 102 I * 10.32.37.128/26 Self 101 I Packet format Message header format Marker: Included for compatibility, must be set to all ones. Length: Total length of the message in octets, including the header. Type: Type of BGP message. The following values are defined: Open (1) Update (2) Notification (3) KeepAlive (4) Route-Refresh (5) note: "Marker" and "Length" is omitted from the examples. Open Packet Version (8bit) Version of BGP used. My AS (16bit) Senders autonomous system number. Hold Time (16bit) Timeout timer, used to calculate KeepAlive messages. Default 90 seconds. BGP Identifier (32bit) IP-address of sender. Optional Parameters Length (8 bit): total length of the Optional parameters field. Example of Open Message Type: Open Message (1) Version: 4 My AS: 64496 Hold Time: 90 BGP Identifier: Optional Parameters Length: 16 Optional Parameters: Capability: Multiprotocol extensions capability (1) Capability: Route refresh capability (2) Capability: Route refresh capability (Cisco) (128) Update Packet Only changes are sent, after initial exchange, only difference (add/change/removed) are sent. Example of UPDATE Message Type: UPDATE Message (2) Withdrawn Routes Length: 0 Total Path Attribute Length: 25 Path attributes ORIGIN: IGP AS_PATH: 64500 NEXT_HOP: 192.0.2.254 MULTI_EXIT_DISC: 0 Network Layer Reachability Information (NLRI) Notification If there is an error it is because one of the fields in the OPEN or UPDATE message does not match between the peers, e.g., BGP version mismatch, the peering router expects a different My AS, etc. The router then sends a Notification message to the peer indicating why the error occurred. Example of NOTIFICATION Message Type: NOTIFICATION Message (3) Major error Code: OPEN Message Error (2) Minor error Code (Open Message): Bad Peer AS (2) Bad Peer AS: 65200 KeepAlive KeepAlive messages are sent periodically, to verify that remote peer is still alive. keepalives should be sent at intervals of one third the holdtime. Example of KEEPALIVE Message Type: KEEPALIVE Message (4) Route-Refresh Defined in RFC. Allows for soft updating of Adj-RIB-in, without resetting connection. Example of ROUTE-REFRESH Message Type: ROUTE-REFRESH Message (5) Address family identifier (AFI): IPv4 (1) Subtype: Normal route refresh request [RFC2918] with/without ORF [RFC5291] (0) Subsequent address family identifier (SAFI): Unicast (1) Internal scalability BGP is "the most scalable of all routing protocols." An autonomous system with internal BGP (iBGP) must have