Update, Notification – H3C Technologies H3C SecPath F1000-E User Manual
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BGP identifier: An IP address that identifies the BGP router
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Opt Parm Len (Optional Parameters Length): Length of optional parameters, which is set to 0 if no
optional parameter is available.
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Optional parameters: Used for multiprotocol extensions, and other functions.
Update
The Update messages are used to exchange routing information between peers. It can advertise a
feasible route or remove multiple unfeasible routes. Its format is shown below:
Figure 3 BGP Update message format
Each update message can advertise a group of feasible routes with identical attributes, and the routes
are contained in the network layer reachable information (NLRI) field. The Path Attributes field carries
attributes of these routes. Each update message can also carry multiple withdrawn routes in the
Withdrawn Routes field.
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Unfeasible routes length: The total length of the Withdrawn Routes field in bytes. A value of 0
indicates no route is withdrawn from service, and the Withdrawn Routes field is not present in this
Update message.
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Withdrawn routes: This is a variable length field that contains a list of withdrawn IP prefixes.
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Total path attribute length: Total length of the Path Attributes field in bytes. A value of 0 indicates
that no Network Layer Reachability Information field is present in this Update message.
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Path attributes: List of path attributes related to NLRI. Each path attribute is a triple
and perform routing and protocol extensions.
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NLRI (Network Layer Reachability Information): Each feasible route is represented as
Notification
A Notification message is sent when an error is detected. The BGP connection is closed immediately
after sending it. The Notification message format is shown below:
Figure 4 BGP Notification message format
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Error code: Type of Notification.
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Error subcode: Specific information about the nature of the reported error.