[unisog] DNS troubles

Michael Holstein michael.holstein at csuohio.edu
Mon Sep 19 12:54:24 GMT 2005


> We'd like to rule out our own gear, firewall, packetshaper, etc. before we go
> blaming the ISPs. But is anyone else seeing DNS troubles with off-campus users?
> Is cache poisoning on the increase this week? Many thanks for your consideration.

I've known several ISPs to block access to port 53 except to their own 
nameservers. I'm not sure if this is for monitoring reasons (eg: spy on 
the customers that use Anonymizer, etc), or to try and prevent DDOS 
using port 53, but I've seen it happen fairly often.

Cheers,

Michael Holstein CISSP GCIA
Cleveland State University


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