[202405][Broadcom-DNX] ebgp session kepts flapping when macsec is enabled

[ysmanman]

Description

In our testbed, we config ebgp with the peer connecting to macsec enabled 400G port. We observed the bgp session kept flapping. After investigation, we found SONiC was not able to tx large size bgp packet to peer because of the following tx error:

TX FIFO Underrun frame TX Error frame

The issue was not seen after we configured very small MTU like 256.

Steps to reproduce the issue:

1. 2. 3.

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[ysmanman]

Add @kenneth-arista @arlakshm @judyjoseph for viz.