For a while it was common for some servers to reject connections from IP addresses that didn't resolve via reverse DNS(*). Since delegating reverse DNS along other than Class C boundaries is a real pain (not impossible, but all 3 ways to do it count as kludges...), an ISP that does it for any of its space might as well do it for all. (*) I don't recall the exact rationale, and it has been a while since I've seen any discussion of it.
David Gillett > -----Original Message----- > From: Terry [mailto:[EMAIL PROTECTED] > Sent: July 31, 2003 02:41 > To: [EMAIL PROTECTED] > Subject: IP address allocation > > > Hi, > > I've googled but haven't really come across anything that answers my > questions. Is it common practice for ISPs to allocate a block of > addresses to a customer and put in DNS records for ones that are > unused? > > For example, xxx.8-xxx.15 is assigned to the customer. Customer uses > xxx.9 for the router and xxx.10 for web server. xxx.11-14 are unused. > I would expect to see DNS records for xxx.9 and xxx.10 but not for the > rest of the block. Am I wrong? If there are DNS records for the rest > of the IPs, why is that? Is there some security reason for doing > this? > > -- > Regards, > Terry > > > -------------------------------------------------------------- > ------------- > -------------------------------------------------------------- > -------------- > --------------------------------------------------------------------------- ----------------------------------------------------------------------------
