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How to deploy the BGP Path MTU Auto Discovery

Latest reply: Dec 25, 2018 15:23:51 1155 6 11 0 0

Path MTU auto discovery allows BGP to discover the smallest MTU value on a path so that BGP messages are transmitted based on the path MTU. This function improves transmission efficiency and BGP performance.

The link-layer MTUs of different networks through which a path traverses may vary from each other. The smallest MTU on the path is called the path MTU.

Path MTUs vary with the path, and the path MTUs may be different in opposite directions. With path MTU auto discovery, BGP can discover the Path MTU from the source to the destination. The path MTU will be encapsulated into TCP IP data during BGP message transmission.

In Figure 8-2, a BGP peer relationship is set up between Device A and Device D. BGP messages are encapsulated into TCP data packets for transmission. Therefore, Device A sends TCP data packets to Device D based on the default maximum segment size (MSS). As a result, a lot of BGP messages are fragmented into different packets, and the number of ACK messages corresponding to these messages increases, leading to a low transmission efficiency. To resolve this issue, configure Path MTU auto discovery. In Figure 1, the path MTU between Device A and Device D is 1496. With path MTU auto discovery, BGP messages are transmitted based on the path MTU (1496), which speeds up BGP message transmission and improves BGP performance.

Figure 1-1 Networking with path MTU auto discovery

                                              111017ozdtdfmkkgndszda.png

In this project the site PE and extend PE not have the direct link with the RR, when a site PE and an extend PE establish a neighbor relationship with the RR, BGP packets pass through multiple paths. If the MTUs of different paths are inconsistent, BGP packets may be fragmented, which affects transmission efficiency and reduces BGP performance.

The configuration template is as below:

Table 1-1 BGP Path MTU Auto Discovery Configuration Template

#

bgp 65000

router-id 1.1.1.1

peer 1.1.1.2 path-mtu auto-discovery

#

commit

#


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dagui
Created Dec 24, 2018 03:11:53

What is the agreement of MTU?
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Yolanda_617
Created Dec 24, 2018 03:34:18

What is the meaning of the BGP path?
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yWX511501
Created Dec 24, 2018 06:14:57

It is clear, hope it will be help
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YOO
Created Dec 24, 2018 07:53:36

If the MTUs of different paths are inconsistent, BGP packets may be fragmented, which affects transmission efficiency and reduces BGP performance.it is very help ful sharing.
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user_2915719
Created Dec 24, 2018 08:07:53

Important notice, if the MTU is not right, it will cause many troubles.
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3li
Created Dec 25, 2018 15:23:51

It's hard
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  • x
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