System Administration

Netgear GS108T VLANs

When you reset the 108T, the system creates three default VLANs.

The Switches and the Router


We have one router, the ZyXEL USG-50, a midrange SOHO router with a bunch of interfaces, support for dual WANs, support for 3G modems, and a disk or flash disk for storing data.

Network Tools

I'm not some kind of network guru, so I tend to stick to simple tools and references. The main reference to study is Wikipedia, which has all the standards covered, and includes some history.

Some Network Design Principles and Conventions

Different admins have different conventions. Here are a list of the ones I'm going to use:

A Small Large Network: USG-50, GS108T, HP 1910

The networking workbench.

ZyXEL ZyWALL USG-50 VLANs

This inexpensive SOHO/Small biz router has a simple and pretty feature-rich implementation of vlan routing.

Netgear GS108T Sample Networks

On all configurations, I'm going to set port 1 to VLAN 1, so that if you need to fix the config, you can plug into port 1 and reset, then go to the default IP address 192.168.0.239.

Netgear GS108T-200


I'm going to trash what little networking cred I have by stating that I like this unit, the Netgear GS108T switch. It's a ProSafe, managed switch. It cost $125 or so after tax, which is kind of expensive for a small switch nowadays.

More Impressions of the ZyXEL ZyWALL USG-50

I've finally started to work on the network because, while things are heating up at work, I'm mostly on-call for the next week. I have some time on my hands to experiment.

HP V1910 Console Cable Pinouts

We just got a couple of these HP V1910 48G switches. These are actually old 3Com switches, but whatevah, they have a web gui and it's designed for the "easy to use" market.

Epson Projector RS323 to Modular (RJ45) Adapter for a Serial Cable, aka a Null Modem

This article explains how to build a serial cable adapter for the Epson projectors. This cable uses two adapters that go from DB9 to RJ45. In between, you use a regular telephone cord.

Backup Write Speeds

This is a scratchpad for noting some disk transfer speeds. There are so many potential configurations, and possible bottlenecks...

Dell PE1800 w/PERC6 SATA 1.5 over USB2 to external HDD, ntbackup.exe, 4.8 megabytes per second.
Home PC disk to disk, 7200RPM, 904MiB directory, 23 seconds. 39.3 MiB/s.

ZyXEL - ZyWALL USG 50 First Impressions


We just got one of these. It's a low-cost firewall. Some folks on forums have said that ZyXEL uses a proprietary OS, ZyNOS, and perhaps they do, but not on this device. The latest firmware download includes a spreadsheet with FOSS software listed, and it includes the Linux kernel and a bunch of popular networking software.

I haven't built Linux firewalls in a few years, so I'm out of touch. The firewall feels a little Linuxy, but there's a layer of configuration objects that helps to glue all the different services together.

Long Delay in Receiving Email from Gmail

A party trying to send me an email via gmail got this error:

From: Mail Delivery Subsystem 
Date: Sat, Aug 11, 2012 at 12:50 PM

Saved by an Old System (Disaster Recovery Story and Case Study)

I had an email spam filter machine (which also did other things). When we got new computers, I figured on replacing the machine. What we did was, basically, copy most of the configuration from the old system to the new system. It wasn't identical, but very close.

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