Still trying to figure out what is going wrong. I'm about to place a call into the data center, to see if they can help.

What you might be seeing is your IP address not responding - but, if you log into your linode via the console, and ping something, then it makes it work again.

The arp responses aren't getting to the gateway, is what I think is going on...

Excuse my ignorance, but what is an arp response?

It has to do with MAC addresses, which are the globally-unique hardware ID, that each piece of networking equipment has.

ARP is part of Ethernet/IP networking - when machine or a router needs to send a packet to a piece of gear, it firsts broadcasts an "ARP who-has this ip" to the network. One of the machines must respond with a "hey, that IP address is-at this MAC address" response.

The response tells the router where to address the packet, using that MAC address.

Ahh. Know all about MAC addresses, so this makes sense.

Well, I spent all day trying to fix this - on the phone with the data center, checking over all the settings, etc.

The problem still exists, but I've implemented a work-a-round. All the IPs should be working normal.

I set up a cron-job to ping all the IPs every minute. This seems to keep the MAC table fresh on the switch, and the IPs working. Although this completely solves the problem, I am a little worried that more problems might exist. We'll run like this for a few days to see how well it works.

The good news is a colleague of mine (and UML expert) David said he could lend his pair of eyes tomorrow - so we'll see what comes of that.

Just thought I'd let you know that I still can't login using the IP address.

When attempting to SSH using my main IP address.. I connect now, which is good.. but it rejects my password. There's actually no textual clue that the password I'm entering is invalid, but the ENTER PASSWORD in F-Secure SSH just repops.. I entered it over and over to no avail...

When logging into each Linode via IP address, you must use a valid user account that has been created on the Linode or login using the root account.

Logging in to Linode's via the console is a different story and you must use your master Linode.com user account and password. Better to login using your IP address though.

Problem resolved.