Strange and horrible network access GUI/SSH

I’ve been trying to get my installation running properly and am having a lot of problems just with accessing GUI, SSH/SCP

I’ve reinstalled multiple times, and even tried different distros…
But upon installing fresh and yum-updating, it takes FOREVER to access anything. And a lot of times it just refuses to.

I am using a Poweredge 1950 server, onboard nics and a Sangoma A101D. Im on a pretty simple network at my company. Most of the time I can boot up, and ping internal and external from the server. But 75% of the time I cannot ping it from anywhere in the network. Even with firewall disabled. I am trying to use FreePBX distro, but have also experienced this with Elastix 4.0.
It seems to be completely intermittent when I am able to access GUI or SSH, and the GUI is very very sluggish and doesn’t want to load pages and often times out.
Ifconfig reports no packet loss on eth0.
At one point I thought it may be the NIC offload option on the server so I removed that, but I don’t really see any difference.
Is there a good way to know what causes this? Is my hardware just too old for the latest FreePBX??

This sounds like a DNS issue at first blush. The fact that it’s intermittent doesn’t help, but the timing out part really does remind me of a DNS error.

I did find someone’s comment about not adding my local domain servers DNS service to the list.
I noticed also that the DNS server list was empty (via GUI) even though I had set my DNS server during setup.
I’ve changed this to loopback address and added googles addresses as well and it seems to be functioning much better at the moment.
Thanks for taking the time to reply. If I notice any further issues I’ll follow up

Ok here is a behavior I am seeing after a server reboot.
The workstation I am using is unable to connect again.
I grabbed my phone, connected to the wifi, and it immediately connected to the GUI.
Workstation still unable to connect…