Frijole wrote: > > There is one major downside to blocking TCP port 53 - some Microsoft clients > will not be able to do host lookups properly. I have seen this on NT 4.0 > with OP4 installed. The SMTP service was polling the dns server using TCP, > not UDP. Searching http://support.microsoft.com I found an obscure article > (that I wish I had saved) which stated that according to the RFC, both TCP > and UDP connections should be allowed on public DNS servers. Once I opened > TCP, the SMTP was able to resolve properly and send messages. It is not a Microsoft issue. The RFC does say that. See RFC1035, sections 4.2.1 and 4.2.2. The MX record that your SMTP server was trying to pull down was probably more than 512 bytes, thus it resorted to TCP. -- Crist J. Clark Network Security Engineer crist.clarkat_private Globalstar, L.P. (408) 933-4387 FAX: (408) 933-4926 The information contained in this e-mail message is confidential, intended only for the use of the individual or entity named above. If the reader of this e-mail is not the intended recipient, or the employee or agent responsible to deliver it to the intended recipient, you are hereby notified that any review, dissemination, distribution or copying of this communication is strictly prohibited. If you have received this e-mail in error, please contact postmasterat_private
This archive was generated by hypermail 2b30 : Mon May 14 2001 - 19:33:06 PDT