The Boston Diaries

The ongoing saga of a programmer who doesn't live in Boston, nor does he even like Boston, but yet named his weblog/journal “The Boston Diaries.”

Go figure.

Tuesday, April 25, 2006




“Hello, Technical Support,” I said.

“Hey, this is F from XXXXXXXX.” It's the cusomter we set up the IP tunnel with DSL backup a few months ago. “Our T-1 was just installed.”

“Okay,” I said, unsure of the implications of what F just said. What does that have to do with us? I'm thinking.

“I was wondering if the T-1 has been installed on your end yet?” asked F.

Excuse me? I thought.

“The T-1 on your end. We're getting a T-1 through you guys,” said F.

“Oh, was that my ‘out loud” voice?”

“Yes,” said F.



That was how I found out about the new T-1 installation for our customer about a week or so ago. They dropped the IP tunnel and decided on a dedicated circuit with us. And they're keeping the DSL backup connection.

Now, the DSL circuit on our end comes in one Cisco router. The dedicated T-1s on our end come into another Cisco router. In this case, the T-1 is the primary circuit and the DSL is the secondary circuit.

Well, either we go static routing and I'm on call 24/7 and can never be more than two minutes from an internet connection so I was rewroute things if the T-1 fails, or we use a dynamic routing protocol like OSPF to handle these things for us.

I'm having to learn to configure OSPF across four routers to get this accomplished.

OSPF is not entirely new to me, but we only have it running between two routers, one on our side, and one to another customer. This customer though, requires OSPF configurations across four routers.

Fortunately, it wasn't that hard to set up, but it's not complete yet.

[Portion of our  network running OSPF]

That firewall between our core router CORE and our DSL router DSL is keeping OSPF from communicating across all the routers—OSPF communicates directly with neighboring routers, and that firewall isn't a neighboring router.

To fix that, I need to:

  1. Set up a virtual OSPF link between CORE and DSL, but that apparently involves multiple OSPF areas, which is something I don't care to get into with a network this small (and frankly, we can get by entirely with static routing if it weren't for the redundant links).
  2. Set up OSPF on the firewall. Easier than the first option, but still requires some work.
  3. Remove the firewall entirely. Nearly all the customers on DSL already have a firewall locally (heck, nearly everything that hooks up to the Internet has a firewall) so removing the firewall isn't that much of an issue.

Of those, the third option is the easiest one to handle.

Once the firewall is out of the way, and the T-1 functions between us and XXXXXXXX, then OSPF will handle the changes in routing in case any of links to our customers go down.

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