Good Morning Valdis > -----Original Message----- > From: Valdis.Kletnieks@vt.edu [mailto:Valdis.Kletnieks@vt.edu] > Sent: 29 October 2002 15:39 > To: Sean Jones > Cc: ietf@ietf.org > Subject: Re: Palladium (TCP/MS) > You're close. You'd want this for multihomed servers, so a > PTR query works > as you'd expect. Consider this case: > www.big-corp.com A 10.0.0.10 > A 192.186.10.10 > mail.big-corp.com A 10.0.0.10 > A 172.16.23.10 > Then you'd want to have PTRs as follows: > > 192.168.10.10 PTR www.big-corp.com > 172.16.23.10 PTR mail.big-corp.com > (and then the magic) > 10.0.0.10 PTR www.big-corp.com > PTR mail.big-corp.com > If you don't have 2 PTR records for that last, you can get > into the situation where a system will look up the A record for www, get the IP > address, then do a PTR to sanity-check, get back only the mail. address, > and get upset. Having both PTR records means that you'll be able to find one > to match to the original hostname either way... Forgive my ignorance, but I thought email was handled by Mail eXchange (MX) records, thus a PTR would not be required? > > Thinking along a bit more, setting the routers shouldn't be > >a big issue, after all Cisco have been producing routers IPv6 capable > >for a fair while now, so surely they could incorporate multiple PTR records > >within the routers capability? > Routers don't have anything at all to do with PTR records. > What I said was that if a company wanted to block all access to > Microsoft's servers, they'd have to keep continual track of all the IP addresses > in use - which can be interesting if round-robin DNS or other similar things > are in use. I understand where I went wrong. But I doubt that any commercial enterprise would want to block access to MS servers in RL. Regards Sean Jones