ISP customer assignments

Thu Oct 22 02:38:39 UTC 2009

In message <op.u156b0mztfhldh at rbeam.xactional.com>, "Ricky Beam" writes:
> On Tue, 20 Oct 2009 19:38:58 -0400, Bill Stewart <nonobvious at gmail.com>  
> wrote:
> > ... If you've got a VPN tunnel device, too often the remote
> > end will want to contact you at some numerical IPv4 address and isn't
> > smart enough to query DNS to get it.
> 
> As I was told by Cisco, that's a security "feature".  Fixed VPN endpoints  
> are supposed to be *fixed* endpoints.  Yes, it is a pain when an address  
> changes, for whatever reason.  But relying on DNS to eventually get the  
> endpoint(s) right is an even bigger mess... how often is the name<->IP  
> updated?

It should be automatically updated by the end point.  We do have
the technology to do that.

> how often do the various DNS servers revalidate those records?  

If you are talking about caching servers then they will honour the
TTL in the records.

> how often do the VPN devices revalidate the names?

At startup.  A well designed VPN protocol will support end point
address mobility.

> what happens when the dns changes while the vpn is still up?

This should be transparent to everything other than the vpn end
points.

> I'll stick with entering IP addresses.
> 
> --Ricky
> 
-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org