Users Guide

1386 BGP
Extended Community Attribute Structure
Each Extended Community attribute has a community type code of 16 and is
encoded into an 8-octet value. The first 2 octets are the attribute type and the
remaining 6 octets contain the value of attribute. The values from 0 through
0x7FFF are assigned by IANA and values from 0x8000 through 0xFFFF are
vendor-specific.
The Extended Community attribute may be represented in multiple ways but
Dell EMC Networking supports only the following two formats:
Two-octet AS specific Extended Community
This is an extended type with Type Field composed of 2 octets and Value
Field composed of 6 octets.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00 or 0x40 | Sub-Type | Global Administrator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Administrator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The value of the high-order octet of this extended type is either 0x00 or 0x40.
The low-order octet of this extended type is used to indicate sub-types.
The Value Field consists of two sub-fields:
• Global Administrator sub-field: 2 octets
This sub-field contains an Autonomous System number assigned by IANA.
• Local Administrator sub-field: 4 octets
The organization identified by Autonomous System number in the Global
Administrator sub-field can encode any information in this sub-field. The
format and meaning of the value encoded in this sub-field should be
defined by the sub-type of the community.
IPv4 address specific Extended Community
This is an extended type with Type Field composed of 2 octets and Value
Field composed of 6 octets.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x01 or 0x41 | Sub-Type | Global Administrator |