November 30, 2023

BGP Attributes Categories

BGP Attributes Categories

BGP Attributes Categories are 1) WELL-KNOWN, MANDATORY , 2) WELL-KNOWN, DISCRETIONARY, 3) OPTIONAL, TRANSITIVE, 4) OPTIONAL, NON-TRANSITIVE. details are: [boxads]

BGP Attributes Categories
BGP Attributes Categories

WELL-KNOWN, MANDATORY

AS-path: A list of the Autonomous Systems (AS) numbers that a route passes through to reach the destination. As the update passes through an AS the AS number is inserted at the beginning of the list. The AS-path attribute has a reverse-order list of AS passed through to get to the destination.

Next-hop: The next-hop address that is used to reach the destination.

Origin: Indicates how BGP learned a particular route. There are three possible types — IGP (route is internal to the AS), EGP (learned via EBGP), or Incomplete (origin unknown or learned in a different way).

WELL-KNOWN, DISCRETIONARY

Local Preference: Defines the preferred exit point from the local AS for a specific route.

Atomic Aggregate: Set if a router advertises an aggregate causes path attribute information to be lost.[adsense]

OPTIONAL, TRANSITIVE

Aggregator: Specifies the router ID and AS of the router that originated an aggregate prefix. Used in conjunction with the atomic aggregate attribute.

Community: Used to group routes that share common properties so that policies can be applied at the group level.

OPTIONAL, NON-TRANSITIVE

Multi-exit-discriminator (MED): Indicates the preferred path into an AS to external neighbors when multiple paths exist.

A list of path attributes is contained in BGP update messages. The attribute is variable length and consists of three fields:

  • ¬†Attribute type consisting of a 1-byte attribute flags field and a 1-byte attribute code field,
  • Attribute length field that is 1 or 2 bytes,and a variable length attribute value field. [bodyads]

The attribute type codes used by Cisco are:

Type Code byte value (as decimal) Attribute Name Category
1 ORIGIN Well-known mandatory
2 AS_PATH Well-known mandatory
3 NEXT_HOP Well-known mandatory
4 MULTI_EXIT_DISC (MED) Optional non-transitive
5 LOCAL_PREF Well-known discretionary
6 ATOMIC_AGGREGATE Well-known discretionary
7 AGGREGATOR Optional transitive
8 COMMUNITY Optional transitive
9 ORIGINATOR_ID Optional non-transitive
10 Cluster List Optional non-transitive
11 DPA Designation Point Attribute
12 Advertiser BGP/IDRP Route Server
13 RCID_PATH/CLUSTER_ID BGP/IDRP Route Server
14 Multiprotocol Reachable NLRI Optional non-transitive
15 Multiprotocol Unreachable NLRI Optional non-transitive
16 Extended communities
256 Reserved for future development

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Shahed

Hi! I am Shahed Israr. I try to help GPON Technology users with their queries and provide them with relevant and accurate information to the best of my ability. My main goal is to assist and enhance GPON Technology user and help people find the answers they're looking for quickly and easily.

View all posts by Shahed →

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