lots of incoming NXDomain-pakets

[Stefan Fournier]

Hi all,

when i log the pakets of port 53 on our DNS with tcpdump, i see lots of
incoming pakets like:

root at tiger> /opt/tcpdump/bin/tcpdump port 53 | grep NXD
tcpdump: listening on lan0
08:11:47.148352 a.root-servers.net.domain >
tiger.assyst-intl.com.domain: 32550 NXDomain*- 0/1/0 (103) (DF)
08:11:47.321099 c.root-servers.net.domain >
tiger.assyst-intl.com.domain: 32554 NXDomain*- 0/1/0 (103) (DF)

So "a.root-servers.net" tells our DNS that a Domain does not exist;
however i cannot find the request from
our DNS to the root-server (i looked for the ID, e.g. 32550).

As we have a dialup internet connection and these pakets come in almost
every second, i would really like
to stop them.

Has someone seen this before and can give me a hint?

Any help is greatly appreciated.


Thanks,
Stefan