[TriLUG] TCP connections taking forever to form?

[Brian via TriLUG]

Hi Gang,

Something very strange is going on with my Centos 7.4 system, which acts 
as my firewall and server of various things.  Mundane operations are 
taking ages to complete and I think I have narrowed it down to a problem 
establishing TCP connections.

I finally tracked down the slowdown by combing through a particular 
shell-script I was using, so my examples below come from that (getssl).

I'm testing with this command:
$ time curl --user-agent "getssl/2.33" -I 
"https://acme-staging-v02.api.letsencrypt.org/"

Running that on my desktop machine (which is downstream of the server) 
gives me a response right away:
[...]
real	0m0.375s
user	0m0.016s
sys	0m0.015s


Running it on the server itself takes AGES:
[...]
real	2m7.775s
user	0m0.076s
sys	0m0.094s

Two MINUTES for a simple http request!  How can I figure out what in the 
world is causing this?  I'm stumped...

TIA,
-Brian