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BGP · PART 1
Attributes
Name Description

packetlife.net
About BGP Type Path Vector eBGP AD 20 iBGP AD 200 Standard RFC 4271 Protocols IP Transport TCP/179 Authentication MD5 Terminology Autonomous System (AS)
A logical domain under the control of a single entity

Well-known Mandatory · Must be supported and propagated 1 Origin 2 AS Path 3 Next Hop Origin type (IGP, EGP, or unknown) List of autonomous systems which the advertisement has traversed External peer in neighboring AS

Well-known Discretionary · Must be supported; propagation optional 5 Local Preference 6 Atomic Aggregate Metric for internal neighbors to reach external destinations (default 100) Includes ASes which have been dropped due to route aggregation

Optional Transitive · Marked as partial if unsupported by neighbor 7 Aggregator 8 Community ID and AS of summarizing router Route tag

External BGP (eBGP)
BGP adjacencies which span autonomous system boundaries

Optional Nontransitive · Deleted if unsupported by neighbor 4 Multiple Exit Metric for external neighbors to reach the Discriminator (MED) local AS (default 0) Identifies a route reflector List of cluster IDs Originating cluster Cisco proprietary, not communicated to peers (default 0) Path Selection
Attribute Description Preference

Internal BGP (iBGP)
BGP adjacencies formed within a single AS

Synchronization Requirement
A route must be known by an IGP before it may be advertised to BGP peers

9 Originator ID 10 Cluster List 13 Cluster ID -- Weight

Packet Types Open Keepalive Update Notification

Neighbor States Idle · Neighbor is not responding Active · Attempting to connect Connect · TCP session established Open Sent · Open message sent Open Confirm · Response received Established · Adjacency established Troubleshooting show ip bgp [summary] show ip bgp neighbors show ip route [bgp] clear ip bgp * [soft] debug ip bgp […] Highest Highest True Shortest IGP Lowest eBGP Lowest Oldest Lowest

1 Weight 2 Local