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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)
      9  TCP/IP Internet Layer (OSI Network Layer) Protocols
           9  TCP/IP Routing Protocols (Gateway Protocols)
                9  TCP/IP Exterior Gateway/Routing Protocols (BGP and EGP)
                     9  TCP/IP Border Gateway Protocol (BGP/BGP-4)
                          9  BGP Detailed Messaging, Operation and Message Formats

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BGP Connectivity Maintenance: Keepalive Messages
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TCP/IP Exterior Gateway Protocol (EGP)
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BGP Error Reporting: Notification Messages
(Page 2 of 3)

BGP Notification Message Format

The format for the BGP Notification messages is detailed in Table 141 and Figure 196.


Table 141: BGP Notification Message Format

Field Name

Size (bytes)

Description

Marker

16

Marker: This large field at the start of each BGP message is used for synchronization and authentication. See the discussion of the BGP general message format for details.

Length

2

Length: The total length of the message in bytes, including the fields of the header. Notification messages are variable in length.

Type

1

Type: BGP message type, value is 3 for Notification messages.

Error Code

1

Error Code: Specifies the general class of the error. Table 142 shows the possible error types with a brief description of each.

Error Subcode

1

Error Subcode: This field provides more specific indication of the cause of the error for three of the Error Code values. The possible values of this field for each Error Code value are shown in Table 143.

Data

Variable

Data: This field contains additional information to help diagnose the error; its meaning is dependent on the type of error specified in the Error Code and Error Subcode fields. In most cases, this field is filled in with whatever bad value caused the error to occur. For example, for “Message Header Error / Bad Message Type”, the value of the bad Type field is placed here.



Figure 196: BGP Notification Message Format

 


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