Having read the FAQs I'm still not quite sure if this is best posted in Network, Software, General or somewhere else, so I'll try general...


Dear all,

Near the beginning of January, I made a few changes to my home system, after which I started to get some unexplained router crashes.

Briefly my network is involves my main PC, running Fedora Core 4, wired to the router. There are three windows laptops connected wireless. The wireless connections have to login into the router's internal VPN server to get anything more than a dhcp assigned address.

The changes I made were:
- I setup samba server in workgroup mode on my desktop. I had to make a couple of changes to the firewall config to get this to work.
- I installed the yumex UI.
- I installed the HP Linux Imaging and Printing (hplip) service and drivers.

The last change I made, because I am considering buying an HP Photosmart 3310. I wanted to check I could at least *install* the linux drivers before I coughed out that amount of money.

After making these changes my previously trusty router (a DrayTek 2600We) crashed four times in two days. My immediate suspicions were samba and hplip, as installing both of these could have introduced new protocols to the network.
- So I disabled hplip and used yumex occasionally. For about two weeks running just samba, I seemed to have no problems.
- Then I started the hplip service again and ran that and samba for another couple of weeks. Again there appeared to be no problem.
- Then I started yumex for the first time in two or three weeks and, bang, straight away the router crashed again.

The crashes are very irregular and I've not worked out how to force them to happen. However I am 98% sure that the router has only crashed when all three of samba, hplip, and yumex have been running. I know that sounds like an insane combination to cause a crash.

Yumex, in particular, seems a very unlikely candidate for causing this problem. I would have imagined that it was simply a wrapper for command-line yum. In the past I've used command-line yum loads without problem. Surely Yumex doesn't change what goes down the wire? Even then, doesn't it just use http and ftp? How can they be causing the router to crash?

I've tried looking in various log files on my machine and on the router. I couldn't find any clues as to what was going on. although I don't really know what I'm looking for.

So my questions are:
(a) does anybody recognise anything about this scenario?
(b) how do I even begin to debug this problem?
(c) at what point should I decide whether or not to go ahead and buy the printer?

Many thanks for your help,
Andy

The first suggestion is to make sure your router has the most current firmware. From the manufacturer's web site, the most recent firmware fixes problems like:

1. Fixed reboot when handling malformed DNS/MX packet
3. DMZ host may crash the router under heavy load.

The second suggestion is to update all your Fedora software, as many people seem not to do this:

yum -y update

If a new kernel is available, reboot to select it.

The third suggestion if you can recreate the problem easily, is to use a packet sniffer like ethereal to capture the packets sents as the router fails:

yum -y install ethereal

Documentation for ethereal is here. Capture multiple failures and compare the last few packets exchanged to see if there is any consistency. If there is, then open a problem report with your router vendor, and provide them the packet trace captures.

Hi Macomoneta,

Thanks for your reply. Shortly after my first post I realised that my firmware was not the latest, and then felt suitably silly for posting a question without checking the basics first - sorry!

Because of the printer buying issue, I wanted check exactly want was causing it, rather than just assuming that a firmware upgrade would sort everything. Basically I'm trying to check that I can reproduce the crashes without hplip running before upgrading the firmware. I'll then check that this is fixed by the upgrade

BTW, it would seem that yumex does change what goes down the wire. From what I can see from the etherreal output, comandline yum appears to query each repo one by one - waiting for the response from one before querying the next. yumex however queries all the repos in one go - resulting in a large number of DNS queries at the begining of any refresh. According to the router's logs, it incorrectly sees the large number of replies from my ISP's DNS server, as a DoS attack. This is what normally precedes a crash.

Anyway, I'm making good progress solving this. I'll post my results latter in the week.

Thanks again,
Andy