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VLANs on a cheap switch

Today I read on tmbinc’s blog about how he modified a cheap Ethernet-switch to be VLAN capable.

With VLANs you can fan out the single built-in Ethernet-interface of your computer to several isolated networks. These cheap switches (you can get them with 8 ports for about 10€) have this functionality because they use the same chips as common plastic routers that separate their three different types of network ports with the same technique and usually connect with a ninth MII-port that’s not being used in a common desktop-switch.

I had tried to do the same in the past, but initially failed as I blew the serial i2c-eeprom during my attempts of programming it, but today I didn’t make any mistakes that destroyed the little thing. As my configuration is different from tmbinc’s, I’ll make it also available in the archive linked to below.

The Process to make your switch (that has to use a RTL8309SB IC) VLAN capable.

1. Get a switch that preferably already has a I2C eeprom to store it’s configuration. Mine had, because it advertised QOS (quality of service) functionality that requires the IC it to be configured by some external memory. I used a Longshine LCS-FS6108, but it’s already 4 years old, so most likely they’ve switched to a different IC already? One never knows.
2. Remove the I2C eeprom. On that particular switch the ground planes are very thick so I wasn’t able to desolder it properly. I just cut off the pins and…
3. Put it on top of a IC socket providing replacements for the severed limbs.
4. Change the contents of the eeprom using your favorite programmer, the text files in the archive linked to below contain some explanations (see details.txt)
5. Put chip back into switch.

The configuration in the .zip-file provides you with 6 untagged ports and 2 tagged ports according to the table below:

Label on Switch	RTL8309SB Port Number	VLANs
8,7	0,1	1, untagged
6,5	2,3	2, untagged
4,3	4,5	3, untagged
2,1	6,7	1…9, tagged
-	MII	Unused

Download Configuration:

20100106_switch_eeprom_vlan.zip (798k)

• switch_eeprom_vlan.dat : VLAN Configuration of Switch, copy contents to eeprom
• switch_eeprom_orig.dat : Original configuration of Switch, Backup
• switch_eeprom_detail.txt : VLAN Configuration with comments
• switch_eeprom_detail.pdf : VLAN Configuration with comments, as pdf

I tested the switch with a Linux machine that has a NVIDIA nForce Gigabit Controller and my OpenSolaris NAS that uses a RTL8111/8168B PCI Express Gigabit Ethernet controller.

Update 2011-02-18: zip-file available again on new server

Random stuff happening…

No Brat with crackbrained Name on Board.

(as seen on a car on the grocery’s parking lot)

Ubuntu & Gdm make me angry.

I installed the new and shiny Ubuntu Karmic on my computer today. Now there’s a speciality: I run the same installation (on a 2nd harddrive) both natively on the computer, but also in a VirtualBox VM.

That’s actually not complicated to setup, and most of the things work out fine, but there’s a remaining wart, which is the X-server needs additional and different configs for native-mode and running under the VM.

In former times, I just set the X-server being run by gdm (in /etc/gdm.conf) to /usr/local/sbin/Xserver.sh and used that shell-script to launch the correct server (with a different config, or even the same config but different “layouts”).

Now the wise men of gnome (gdm programmers) and Ubuntu decided to hardcode the paths of every component involved… And I only found out after learning…

1. that gdm no longer looks at /etc/gdm/gdm.conf, but rather is configured via the gconfd-mechanism
2. that the X-server configuration is not included in the new mechanism, but rather a compile-time default is hardcoded
3. that the X-server is not run directly, but rather via the wrapper /usr/bin/X, which is, indeed, configurable… but also lacks a configuration directive to choose which server to run.

So, again, in the sake of… “simplification”, or should I say dumbing-down, of their core programs, they made deviating from their “single user on a dedicated machine with internet dial-up” standard scenario even more painful. I might just use MS Windows then, because it basically adheres to the same “do what we have forseen and don’t deviate” belief.

Immediate update: One can adjust the symlink /etc/X11/X! Which isn’t documented (as far as I see) and also not as flexible as the original gdm.conf solution, but should suffice.

Opera 10.1 Upgrade FAIL!

Opera just announced the existence of a upgrade to it. I told it to proceed, shorty after I noticed my (usually silent) PC to spin its fans vigorously…

 

This repeats whenever Opera is restarted, so I had to delete the offending file somwhere in %TEMP%. Great engineering, guys!

Broken Kepco Power-Supply

One of the reference values is much  too low, note the brown and crispy Zener.    

 

Update: Looks very shitty, but it works. I’ll replace those with real 6.2V Zeners the next time I order some electronics stuff.

LCD working

I spent a little while debugging my microcontroller code.

LCD - Update

Success! Even though I’m still scratching my head about the funny memory layout in graphics mode when using a 6x8 font. Time to read the datasheet (again).

Graphical LCD Controller

New project: Using a Atmel ATmega168 to control a graphical Everbouquet LCD that itself uses a T6963C Controller. Right now it seems that I can read the status-register and data successfully. The integrated DC/DC controller (for the negative LCD driving voltage) powers up and delivers –9V.

 

Running, three times…

Vacation

Currently on vacation.

Copying VHS to DVD...

After fighting with Linux's v4l2, alsa, pulseaudio, mencoder, mjpegfoobarblahblubbtools etc.. I just borrowed one of those. Probably it will just work.

*This* is my ambition.

Three Phase Power

Breadboard

I started playing around with a breadboard. Until now, I never had done this, but I have to say, it’s kind of convenient. The only downside: I don’t have pre-cut cables, so I used the one from a big spool I found, but they are kind of pink-ish ;-).

Gainclone

It hums. And I’m annoyed.

 

What did I do on Saturday? Well, via the wonder of the web, I watched my friend burn both himself and his baby daughter with his home-made amplifier, then rail against excel and python in an attempt to print out some gradesheets. He eventually got so angry he threw himself out the window. He was in the basement, but you have to appreciate the attempt.

Update: I modified the last stage to have less gain (4 instead of 20), so it better matches my source, furthermore I added a 5k resistor at the input to have less input impedance. That helped a lot.

i can has censorship

Our junta of incompetent politicians have passed the law that will now introduce censorship in Germany. Ignorant assholes.

device-mapper ate my linux installation

Just a quick note about the harm that you can suffer, should you try to install the “dmraid” package in your linux distribution: It’s EVIL! The problem is that for me it installed the dmraid signature in my harddisks last sector, so that Ubuntu’s initrd would automatically create useless mappings from…

• /dev/sda –> /dev/mapper/NVIDIAxyzqwert
• /dev/sda1 –> /dev/mapper/NVIDIAxyzqwer_1
• /dev/sda2 –> /dev/mapper/NVIDIAxyzqwer_2
• …and so on…

Everything completely pointless, and wrecking my distribution’s ability to boot. I usually run my self compiled kernels which exclude the device-mapper for this exact reason, but it’s not possible on my other PC for one reason or the other. And the final and correct cure is to boot with the greatest bootable live-system there is: GRML, and overwrite the harddisk’s last sector (which holds the signature) with zeroes:

# dmsetup remove_all # get rid of the mappings
# cat /proc/partitions
…
8 0 12345678 sda # your harddisk
…
# sdd bs=512 –inull of=/dev/sda oseek=12345677k count=1 # overwrite last block

Reboot and enjoy. Use this recipe at your own risk!

Pointless^∞

There’s a post over at slashdot about the Twitpocalypse… What it’s supposed to mean is that twitter, this stream of useless short-messages you can (or, if you are like me: you don’t) follow to be informed about the social life or bodily functions of your peers now has accumulated over 2³¹ items, a number exceeding the range of a 32bit signed integer. I’ll never understand how anyone can care about such a thing, but it for sure made it’s inventors famous and rich. And there’s one comment about the stupid choice of words and names I think is especially hilarious (see screenshot).

Vintage moving coil meter

I put some of my electronics garbage to good use, this pretty instrument was salvaged from the dumpster a long time ago. It displays Neper with a full range of +0.5Np at 40µA, 0Np at 24µA.

Pirate Bay Anthem

It might not be one with the most highbrow lyrics, but The Pirate Bay now has an anthem! YouTube Video, PirateBay News, mp3 torrent.

New Mascot

I got myself a new mascot. Somehow reminds me of the fabulous Creatures In My Head. Previously.

News! (Olds?)

Ok, so there hasn't been much activity in this blog since... ages. I left the physicist's natural habitat (university) to work in industry. That said, I hope that the frequency of posts will rise now that I got accustomed to doing "real work". As prearrangement I already changed the subtitle of this blog, maybe I should also hold a "Blog Reader Kick-Off Awareness Meeting"?

200000 km

My trusty old Polo had its kmversary...

msdnaa fail

To download a ISO image for Windows XP (as a member of a university, I joined the Microsoft Developers Network Academic Alliance programme) I have to download a special windows-only binary program... Which doesn't work right in WINE (the windows API for Linux). But they didn't even get it right on Windows either, as the screenshot here suggests.

Back from holiday.

Thunderbolt

Finally my nice GPS disciplined clock arrived.