[TriLUG] OT: DNS reverse lookups

Geoff Purdy geoff.purdy at verizon.net
Mon May 20 16:43:35 EDT 2002


> > Do you think traffic from my IP address is being blocked by their firewall,
> > or is there a better explanation I've overlooked?
> 
> I thinkt that the configuration of those ftp servers contain "!nameserved" 
> string in the addrglob entry. That is, if your IP address cannot be resolved 
> to your hostname, you are not allowed to sue the service.


Thanks for the clarification.  I may have phrased my original post poorly by intermingling two largely separate issues.  I'll try to re-state it more clearly.

Given the following:
1)  I've had frequent problems with reverse lookups failing with our ISP
2)  Prior to attempting to access the FTP service on this particular server, I was able to access their HTTP server without any problems.
3)  Subsequent to attempting to access the FTP service, all traffic (FTP, HTTP, ping) recieves no response at all.
4)  All of these services are accessible from other hosts (i.e. fatalpha.trilug.org)

Is it common practice for a firewall's rules to be configured to in such a way that traffic which fails reverse lookup would be considered 'suspicious' (i.e. a DoS attack) and the firewall would subsequently block all traffic originating from that IP address?


As a separate issue, has anyone else had reverse lookups fail with Time Warner and, if so, can offer any tips on getting the issue resolved?


I'm sure I'll get this figured out with TW eventually, I was just wondering if these were common problems.  Thanks in advance for any suggestions.







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