| EGP, Exterior Gateway Protocol |
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Description | Glossary | RFCs | Publications | Obsolete RFCs |
| Protocol suite: | TCP/IP. |
| Protocol type: | Transport layer exterior routing protocol. |
| IP protocol: | 8. |
| SNMP MIBs: | iso.org.dod.internet.mgmt.mib-2.egp (1.3.6.1.2.1.8). |
| Working groups: | |
| Links: |
EGP exists in order to convey net-reachability information between neighboring gateways, possibly in different autonomous systems. The protocol includes mechanisms to acquire neighbors, monitor neighbor reachability and exchange net-reachability information in the form of Update messages. The protocol is based on periodic polling using Hello/I-Heard-You (I-H-U) message exchanges to monitor neighbor reachability and Poll commands to solicit Update responses.
| MAC header | IP header | EGP header | Data ::: |
EGP header:
| 00 | 01 | 02 | 03 | 04 | 05 | 06 | 07 | 08 | 09 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Version | Type | Code | Status | ||||||||||||||||||||||||||||
| Checksum | Autonomous System | ||||||||||||||||||||||||||||||
| Sequence | Data ::: | ||||||||||||||||||||||||||||||
Version.
8 bits.
EGP version.
Type.
8 bits.
The type identifies the message type.
Code.
8 bits.
The code identifies the message code (subtype).
Status.
8 bits.
The status contains message-dependent status information.
Checksum.
16 bits.
The EGP checksum is the 16-bit one's complement of the one's complement sum of the EGP
message starting with the EGP version number field.
When computing the checksum the checksum field itself should be zero.
Autonomous System.
16 bits.
The assigned number identifying the particular autonomous system.
Sequence.
16 bits.
The sequence number is for the send state variable (commands) or receive state variable
(responses and indications).
Data. Variable length.
RFCs:
[RFC 827] EXTERIOR GATEWAY PROTOCOL (EGP).
[RFC 888] STUB EXTERIOR GATEWAY PROTOCOL.
[RFC 890] Exterior Gateway Protocol Implementation Schedule.
[RFC 904] Exterior Gateway Protocol Formal Specification.
[RFC 911] EGP GATEWAY UNDER BERKELEY UNIX 4.2.
[RFC 975] Autonomous Confederations.
[RFC 1004] A Distributed-Protocol Authentication Scheme.
[RFC 1092] EGP and Policy Based Routing in the New NSFNET Backbone.
[RFC 1156] Management Information Base for Network Management of TCP/IP-based internets.
[RFC 1066] Management Information Base for Network Management of TCP/IP-based internets.
[RFC 1158] Management Information Base for Network Management of TCP/IP-based internets: MIB-II.
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Description | Glossary | RFCs | Publications | Obsolete RFCs |