I recently signed up for an account on box.net so that I’d have another way to store and transfer files between sites. Currently, you can get 1GB of space with the free basic account, but you aren’t allowed to upload files over 10MB. This is fine as long you’re uploading photos, but more problematic if you’ve got larger files.
You are currently browsing the monthly archive for March 2007.
I’ll go ahead and note that to actually get a search result that has to do with ’session 15′ in the Cisco sense, “session 15 cisco” returns exactly what you’d expect (per google.com). If things haven’t changed, that search should give you a top result related to the Cisco 6500 series MSFC. The ’session 15′ (or 16) comes into play when you’ve got such a card in your Catalyst 6000 and you want access to it from the switch’s brain, the supervisor engine (SE).
I’m not normally fixated on ’session 15′ or sessions numbered 15, but as long as I’ve gone this far, I might as well give a little more explanation for why I care what google says about it, and why I chose it for the blog title. The story, in which the completely unexpected, eldritch power of ’session 15′ was revealed to me, is from early in my networking life.
It was early afternoon at Brabanx Inc. , and we had recently received a new 6506 switch. Working with another admin, I had unboxed and powered on the switch in the lab. The two power supplies came up, the switch booted, and the fans shot air through the idle system, as frantic as if the switch was pushing out of hurricane of packets. The fans, though, were all right. I was goofily excited myself, eager to get the switch online and working. I’d never started an installation from scratch with one of these 6500s, and I planned to get it squared away in an hour or two, report to the upperlings, and pat myself on the back the rest of the day. The only problem was, we couldn’t find a way to console into the router card. Vlans were great and nifty, shiny new switchports were wonderful, but we also needed the 6500 to do some serious routing, and without getting into the router card, we weren’t getting anywhere.
Here’s something very useful if you do config changes and maintenance on routers that are farther than are farther away from you than a door or two down. (Especially if you’ve got fast routers with quick reload times.) This is something I use a lot when I’m working on routers at other sites or datacenters, when I’m doing something potentially dangerous on that device like making ACL or routing changes. If you don’t have out-of-band access (e.g., a modem attached to your router with a dial-in line actually plugged in) or an immediate contact at the location where your router is, you can kill your connection with one typo or badly planned line. And then your communication is going to be down until you figure out a way to get into the router or have it rebooted. That’s where the reload commands come in. If I’m about to do something potentially disruptive (something that might lead to a dropped circuit or customers waiting for data to get through, what management might call ‘catastrophic failure’) I frequently write mem (or copy run start) before making any changes, then type in ‘reload in 5′. Or maybe reload in 10, or 15. No ‘conf t’ necessary in any case. It depends on how long your change is going to take (before you get to the point where you break things), and how long the connection can hang out, dead, waiting for revival. What this does, in case it isn’t immediately clear, is it tells your router to reboot itself in X minutes, unless you intervene and countermand that order. In this case, you stop the countdown by using the ‘reload cancel’ command. Shortenable to ‘relo c’, if you’re barely getting there in time.
You can also use a time-scheduled reload by using ‘reload at’ instead of ‘reload in,’ and the details there are much as you would expect. If this suits your purpose or your style better, go with that.
The biggest word of caution is, don’t pat yourself on the back and start doing something else when your configuration change goes without a problem. Your router is going to reboot unless you tell it not to, so remember to cancel it if your perfect config has already been put in place, and things are better instead of worse.
In a weird sort of coincidence, I googled ’session 15′ today, and the first result that came up was a page called ‘Session 15. Planetary Nebulae.’ Even stranger, the page is from a meeting that took place in Austin, TX, where I am based. I copied the text from the result:
Session 15. Planetary Nebulae
| Session 15. Planetary Nebulae. Display, Wednesday, January 6, 1999, 9:20am-6:30pm, Exhibit Hall 1. 15.01 Detection of New Planetary Nebulae from A Complete … www.aas.org/publications/baas/v30n4/aas193/S150.htm - 4k - |
These notes were written to focus on the Cisco implementation of QoS, but I’ll eventually cover enough generic QoS components to make looking at this worthwhile for non-proprietary QoS review. Unless a tile falls from the roof and kills me, etc.. (For Kierkegaard — wiki. )
I recently took the Cisco 642-642 quality of service certification, and the notes are from that study. The 642-642 cert works for the CCVP or the CCIP, but I was more interested in it from the perspective of getting a grip on the subject for the purpose of the routing and switching CCIE.
My original notes were more or less cram notes — I’ll try to put together something more intelligible here.
QoS tool categories:
- Classification and marking
- Queuing / Congestion Management
- Shaping and policing
- Congestion avoidance
- Link efficiency
- Call admission control
1. Classification and marking
Pure marking tools –
- Class-based marking — CBM [including Network-based application recognition -- NBAR (Cisco only)]
Marking plus other functionality –
- policy based routing — PBR
- QOS policy propagation through BGP — QPPB
- Committed Access Rate — CAR
Available markers for QoS sorting (classification):
- IP precedence bits cisco site (from the traditional TOS field, compare with DSCP)
- QoS group [0 to 99; 0 is default, 0=unassigned] — requires CEF (and Cisco)
- DCSP bits wikipedia (replacing, but backward-compatible with, the traditional TOS field)
- 802.1Q / ISL CoS (class of service) aka priority tag — trunking layer-2 link required
- Frame relay DE (discard eligible) bit — if you’ve got frame-relay involved
- ATM CLP bit cisco1 cisco2 — if you have ATM, otherwise not damned likely
- MPLS experimental bits ipinfusion wikipedia — if you have MPLS, otherwise not damned likely
Changing my default mail client in Ubuntu turned out to be one of the easiest config changes I’ve ever made in Linux. In Ubuntu 6.10 (Edgy Eft), the default mail application is Evolution, and I had been putting off changing this to the application I really used — Mozilla’s Thunderbird — because (based on past experience with desktop Linuxes) I was expecting this to be a painful process. Ultimately, I didn’t have to touch Firefox (my default browser, from which I’m launching ‘mailto’ events), I didn’t have to manually edit any configuration files, and I didn’t even have to look very far.
Yesterday, I was trying to find a good way to use an ‘AND’ function in Cisco IOS pipes, to complement the ‘OR’ function available through the ‘|’ symbol (which is to say, the same symbol as the pipe).
For example, if you wanted to show the running config, and filter out lines that contained either ‘foo’ or ‘bar’, you could type
show run | include foo|bar