This behavior started two weeks ago which I am trying to troubleshoot.
Machine A on Lan connects to Machine B external: connection drops directly
Machine C on Lan connects to Machine B external: connection OK.
Machine C on Lan connects to Machine A on Lan: connection drops directly
Machine A on Lan connects to Machine C on Lan: connection drops directly
Machine D on Lan connects to Machine C on Lan: connection drops directly
Machine D on Lan connects to Machine A on Lan: connection OK.
No settings changed on local Firewall.
No settings changed on company Firewall and Proxy.
Any idea what to check more?