+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Identification # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Description:
A gateway that wants to receive an NR message from an
Exterior Gateway will send an NR Poll message. Each gateway
mentioned in the NR message will have an interface on the
network that is in the IP source network field.
EGP Version #
1
Type
2
Code
0
Checksum
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. For computing the checksum, the
checksum field should be zero.
Autonomous System #
This 16-bit number identifies the autonomous system
containing the gateway which is the source of this message.
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RFC827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Identification Number
An identification number to aid in matching requests and
replies.
IP Source Network
Each gateway mentioned in the NR message will have an
interface on the network that is in the IP source network
field. The IP source network is coded as one byte of
network number followed by two bytes of zero for class A
networks, two bytes of network number followed by one byte
of zero for class B networks, and three bytes of network
number for class C networks.
Interval
The polling interval in minutes.
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RFC827 Bolt Beranek and Newman Inc.
Eric C. Rosen
NETWORK REACHABILITY MESSAGE
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! EGP Version # ! Type ! Code !U! Zeroes !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Checksum ! Autonomous System # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Fragment # !# of last frg. ! Identification # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! IP Source Network !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! # of Int Gwys ! # of Ext Gwys !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! # of Nets ! ; # of nets for
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Gateway 1
! Gateway 1 IP address (without network #) ! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net 1,1 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net 1,2 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance !
+-+-+-+-+-+-+-+-+
.
.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net 1,m !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; m nets reachable
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ; via Gateway 1
.
.
+-+-+-+-+-+-+-+-+
! # of nets ! ;number of nets for Gateway n
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Gateway n IP address (without network #) !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net n,1 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance !
+-+-+-+-+-+-+-+-+
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RFC827 Bolt Beranek and Newman Inc.
Eric C. Rosen
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net n,2 !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; 1, 2 or 3 bytes
+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! distance ! .
+-+-+-+-+-+-+-+-+ .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! net n,m !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ; m nets reachable
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ; via Gateway n
! distance !
+-+-+-+-+-+-+-+-+
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RFC827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Description:
The Network Reachability message (NR) is used to discover
which networks may be reached through Exterior Gateways. The NR
message is sent in response to an NR Poll message.
EGP Version #
1
Type
1
Code
0
Checksum
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. For computing the checksum, the
checksum field should be zero.
Autonomous System #
This 16-bit number identifies the autonomous system
containing the gateway which is the source of this message.
U (Unsolicited) bit
This bit is set if the NR message is being sent unsolicited.
Identification Number
The identification number of the last NR poll message
received from the neighbor to whom this NR message is being
sent. This number is used to aid in matching polls and
replies.
Fragment Number
Which Fragment this is in the NR Message. Zero, if
fragmentation is not used.
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RFC827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Number of Last Fragment
Number of the last fragment in the NR Message. Zero, if
fragmentation is not used.
IP Source Network
Each gateway mentioned in the NR message will have an
interface on the network that is in the IP source network
field.
# of Interior Gateways
The number of interior gateways that are mentioned in this
message.
# of Exterior Gateways
The number of exterior gateways that are mentioned in this
message.
# of Networks
The number of networks for which the gateway whose IP
address immediately follows is the appropriate first hop.
Gateway IP address
1, 2 or 3 bytes of Gateway IP address (without network #).
Network address
1, 2, or 3 bytes of network address of network which can be
reached via the preceding gateway.
Distance
1 byte of distance in # of hops.
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RFC827 Bolt Beranek and Newman Inc.
Eric C. Rosen
EGP ERROR MESSAGE
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! EGP Version # ! Type ! Code ! Unused !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Checksum ! Autonomous System # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Error Type ! Error Code ! Id. # of Erroneous Msg. !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
! Sequence # !
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Description:
An EGP Error Message is sent in response to an EGP Message
that has a bad checksum or has an incorrect value in one of
its fields.
EGP Version #
1
Type
8
Code
0
Checksum
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. For computing the checksum, the
checksum field should be zero.
Autonomous System #
This 16-bit number identifies the autonomous system
containing the gateway which is the source of this message.
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RFC827 Bolt Beranek and Newman Inc.
Eric C. Rosen
Sequence Number
A sequence number assigned by the gateway sending the error
message.
Error Type
The Type of the EGP message that was in error.
Error Code
The Code of the EGP message that was in error.
Identification number of erroneous message
The Sequence number of the EGP message that was in error.
Reason
The reason that the EGP message was in error. The following reasons
are defined:
0 - unspecified
1 - Bad EGP checksum
2 - Bad IP Source address in NR Poll or Response
3 - Undefined EGP Type or Code
4 - Received poll from non-neighbor
5 - Received excess unsolicted NR message
6 - Received excess poll
7 - Erroneous counts in received NR message
8 - No response received to NR poll
9 - Not all fragments of NR message received