Hi ,
Forget about my last reply , as I saw you captured the Full stream of ( Client and server side ).

It's very clear that Rest comes from IPs ( 173.235.20.160 & 161 ) which your Backend servers.

I see that your Servers couldn't able to establish 3-way handshake with Bigip , Servers reject the First SYN Packet from Bigip , but the most confusing me how the https health monitor marks your pool as up and at the same time bigip can't establish with servers 3-way handshake on real data traffic.

>>> I found something strange to me :

Do you see MSS value ? it's 1212 which not the standard , it's very very important to check your backend servers's MTU and the MTU in Bigip server side must be compatable with your backend servers that's why your servers Reset this connections , make sure that MTU matches each side ( Bigip server side and Backend servers )

I will tell you another idea >>> What about take a packet capture for your heath monitor to see while monitoring Bigip sends monitor packet with this MSS = 1212 or not as from your pool configuration I see the Https monitor marks your Backend servers Up and Can establish 3-way handshake correct.
So we need to compare between Client traffic on server side and Health monitor traffic on server side as well.
Concentrate more in the server side not ssl certificates.

I will be waiting your results 🙂

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