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Knowledge Base

How Do NEs Convert Between BGP AS Numbers of the Floating Point Type and Those of the Numeric Type?

Publication Date:  2019-05-13  |   Views:  376  |   Downloads:  0  |   Document ID:  EKB1100015043

Contents

Issue Description

Device model: NE40E-X3

Software version: V600R008C10SPC300

Symptom:

       During EBGP deployment, the customer found that the local AS number is 38372 and the peer AS number is 135373. However, the BGP peer statistics on the local device show that the AS number is 2.4301.

Solution

The conversion formula is as follows:

Number before the decimal point X = AS number/65536 [round-up]

Number after the decimal point Y = AS number - (65536 x X)

X and Y are represented in the floating point format.


Taking AS = 135373 as an example:

X = 135373/65536 = 2.0656280517578125 [integer 2]

Y = 135373-65536x 2 = 4301

X and Y are represented in the floating point format as [2.4301]


Run the following command to change the 4-byte BGP AS number as an integer:

<HUAWEI> system-view

[HUAWEI] as-notation plain


This command does not affect the BGP peer relationship or the learned BGP routes.

However, this command affects the AS-Path regular expression and the matching result of the extended community attribute filter.


Perform the following operation:

Use the AS-Path regular expression (ip as-path-filter) to convert a floating point to an integer.

Use the extended community attribute filter (ip extcommunity-filter) to convert a floating point to an integer.