[clug] Tor and other things that go bump in the night

Ben Nizette bn at niasdigital.com
Sat Oct 2 17:34:32 MDT 2010

On 02/10/2010, at 7:07 PM, Keith Goggin wrote:

> Hi List,
> On Thursday morning last I noticed what seemed to me to be a DNS lookup 
> failure on my Bigpond Wireless Broadband connection. The account remained 
> unusable until Friday night even though my 7.2 Home Network Gateway passed all 
> diagnostic tests and could establish a link to the remote tower. 
> When using Firefox, URLs would not resolve with the 'Server Not Found' message 
> yet when I typed in the IP address of www.google.com.au ( the 
> Google Australia page loaded OK.
> My Email Client stopped working with 'unknown host: securemail.bigpond.com' 
> and my VOIP box also died.
> However I also noticed that switching from Bigponds 'Automatic Assigned DNS' 
> to a public or third party DSN server did not fix the problem. Which led me to 
> suspect that Telstra/Bigpond were experimenting with something upstream of the 
> DNS server possibly Conroys Filter.

Hehe, if you hear hooves assume horse, not zebra ;-)

For me this particular clip-clop reminds me of a router firmware bug on the CISCO SRP527W we have at the office.  That router sometimes starts introducing massive latencies to the outside world, we're talking >2s.  When this happens DNS requests time out but for some reason HTTP requests straight to the IP don't (the download speed isn't affected, just latency, so the page load isn't even massively slow).  If someone with a better idea of network quirks knows what would differentiate a DNS and HTTP request in this way I'd love to know!

In my case it's a known firmware bug but, despite the router being less than 3 months old, CISCO won't give me the new firmware without paying for a support contract.  In the mean time reading the firmware changelog I noticed that it's a problem with the connection keep-alive not working correctly so I just wrote a CRON script that pings the next hop every 10 min, keeps the connection alive, avoids the firmware bug, saves me the cost of a support contract and doesn't require a conspiracy theory :-)


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