New remote Spectrum Landscape doesn't connect to main location server

Products

• CA Spectrum

Issue/Introduction

I installed a new SpectroServer in one of our remote locations but this SpectroServer doesn't build a TCP/48879 connection to MainLocationServer on our site.
I checked .hostrc and /etc/hosts on both sides. Looks good for me.  ICMP works fine between both.
I also checked firewall rules for ports 48879 and 56063 (can connect with telnet).
There is a TCP connection from new SpectroServer to MainLocationServer process:
tcp        0      0 x.x.x.x:46802      y.y.y.y:56063      ESTABLISHED 25683/LocServer

I can also find new SpectroServer and landscape in location map.
There is also another landscape at this location that can also not connect to MLS after a network change. 
The location is now connected by another routing path. But ports and connectivity are available.

Environment

Release : 20.2.x

Component : SPCCSS - Spectrum Core / SpectroSERVER

Cause

Networking issue.

Because of different MTU sizes in the new routing path we got incorrect  TCP checksum for TCP segments.

Resolution

After adopting the MTU size the connection could be established between MLS and remote SpectroServer.