This week, as a result of a software upgrade operation across the backbone routers, I had to do the procedure on one of the CRS-1 routers in Stuttgart, since I kinda live in the neighborhood. I have worked, configured and troubleshooted them since 2 years now but physically I only saw one a little in one of our labs. This time I had the opportunity to work a bit more closely with it.
The Cisco CRS-1 Carrier Router System is, as the name suggests, a carrier-grade backbone router which is usually found in big ISP’s. In it’s full 16-slot configuration it can push data up to 92 Tbps (yes, that’s Tera) and the price of such a configuration can make lesser people faint. The CRS routers we’re using are the medium 8-slot version, which is slightly cheaper and it’s not completely packed with line-cards. Of course, this is not the “cheaper” definition we know, it’s still there in the stratosphere. It’s a monster of a router as well, just the chassis with the fans has about 150kg. The full configuration for the 8-slot version, together with the power shelves and line-cards can weight up to 250kg.
The CRS has a highly redundant design, it’s extremely scalable and it’s designed for an “always-on” operation. As software, it runs the IOS-XR which while it has the same look-and-feel as the normal IOS we know, it’s based on Linux. The CRS routers we use form the core of our MPLS network, based on 10GB Ethernet.
The software upgrade was an interesting experience. The new version comes on two 4GB PCMCIA flash cards (one for each router processor) which you have to use to replace the existent flash cards. The procedure is quite different than the one for a normal router and it’s quite lengthy. It involves first rebooting the router which loads the new software on the route processors and then each individual line-card has to be upgraded as well. All-in-all I was in that data-center for two and a half hours.
This particular data-center belongs to KPN and, like almost all their sites in Germany, they are completely unmanned. You need to call first and they open the door for you all the way from Netherlands. Same when you get out, you’re stuck in there until they open the door for you.
It was nice experience. And even though it took a long time, at least I could kill time by reading a SciFi ebook (“Consider Phlebas” by Iain M. Banks) on my N85 and listening to music. Good book too, I like it so far.