Recommended tcp-mss size on BGP over GRE with IPSEC VPN

[stevebiko]

Hi guys,

I already have BGP over GRE tunnels between our DC and DR site and I want to overlay IPSEC now. I was wondering if there is a recommended tcp-mss size on BGP over GRE with IPSEC VPN ? Kindly assist.

[Joseph W. Doherty]

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Yes, I would say whatever is suitable for any of your TCP traffic (which includes BGP).  (NB: on Cisco routers, you often have to enable PMTUD for BGP to use more than 476 packet sizes.)