Connecting to RDS Postgres from remote machine

Step 4 of the RDS setup wizard ("Additional Config") lets you select whether the DB is Publicly Accessible or not (if it's not, access is limited to within your VPC, regardless of your security group settings). I'd imagine that determines whether the hostname resolves to 54.* vs 172.* .

Your first instance may have been set to private - as far as I can tell this can't be changed after initialization. I had a similar issue and creating a new instance set to be publicly accessible solved it for me.

My company's firewall had blocked outgoing traffic to the default postgres port, 5432. I didn't realise this until I tested the port using netcat in a terminal window, as follows:

nc -zv portquiz.net 5432

Hopefully this saves someone half a day of messing around with AWS security groups.

Absolutely there is. I have pgadmin loaded on my local machine connected to my RDS instance. |

I just confirmed that I can connect using the same syntax you used for psql, although the -U was not necessary for me (I still included both "example" parameters though)

I did edit the "default" security group and added my IP (Ip of the machine I'm connecting from)/32 to be allowed, although I'm sure you could get less restrictive than that, but I'd start there and see if it helps.