OK, “TechRepundits”, here’s one from the annals of networking hell.
My company was called in by a High School to resolve Internet access issues they had been having partly due to (and since) Hurricane Ivan “The Terrible”.
Ivan took out several of their lines, including the line used for their ADSL access. ADSL connection: 768 kbps (down)/ 256 kbps (up). The telephone lines were reconnected, but since then the service had been considerably poor (in their words). When we were called in the line had previously been disrupted again, and service had just been restored. The “technicians” at the school had NO idea as to how to configure the modem. The original config had the modem connecting to a single machine on the network (Network uses CNSH1600 switches, unit to which modem was attached had two NIC’s) We did a reconfiguration, ran a connection directly from one of the switches to the modem, and had everyone getting access (though service left a little to be desired, wasn’t too great, wasn’t “terribly poor”). This was done on a Saturday, by Monday morning NOBODY had a connection!!!! The DSL line kept “dropping out” – you would literally see the line sync light disappear then come back after a few minutes.
However, I have yet to explain the physical infrastructure of the school’s networks (that’s right plural networkSSSS).
____________
___ ~30 Yds | |~20 Yds _______
| |———| |——–| |
|___| |____________| |_______|
Admin Library/Comp. Lab2 Comp. Lab1
OOOOOOPS! That was awful!!!
***************____________************
_____~~30 Yds |____________|~20 Yds _______
|___|————-|____________|———-|_______|
|___|…………….|____________|………….|_______|
Admin______Library/Comp. Lab2_______Comp. Lab1
Hope this quasi-diagram does some justice. In all we have more than 150 computers feeding from the DSL connection. Admin has 16 machines, Library ~72, and Comp Lab1 ~70. Additionally, there is a standalone computer used by a teacher that is also connected. The networks are interlinked by cat5 cables running from their respective switches into the switch in the Library. Each network has a server (windows 2000 server in each case).
Now, when the adsl connection is setup on a standalone machine it blazes!!! Rip-roaring speed!! Drop it back onto the switch and everything goes south! Slow or non-existent service.
We also found that at times (though not consistently so) removing, say, ADMIN or all external networks would improve the quality of service in the Library (where the ADSL connection is physically located, BTW), but the improvement was never one of great speed, more akin to a fast dialup. Also if we took the ADMIN interlink cable out of the Library switch (essentially isolating ADMIN) and plugged it directly into the modem, (i.e. ADMIN ONLY connected to the modem) the service was still poor to non-existent, and very inconsistent.
Library server is running Symantec NAV Corp ED, protecting all machines connected to Library network, we did a random check on several machines found little or no spyware/malware. ADMIN machines were infested with viruses (OK, maybe I exaggerate – but just a little), almost every unit had at least one virus, and an average of ~20 spyware/adware threats (some were a great deal more). We cleaned the machines of all threats – virus/spyware – checked connection speed with only ADMIN connected to the modem and….SHAZZAM!…. still poor connection speeds.
What say you great minds of TechRepublic???!!!
ADDENDA:
i) Networks are using 192.168.etc. IP range
ii) Modem was 10.0.0.138 by default, but changed to 192.168.0.1 to work on the network
iii) All servers run their own DHCP, using 192.168.0.1 as router/gateway
iv) 192.168.0.1-30 are reserved, DHCP’s only hand out from 31 up