default $ttl

[Mark.Andrews at nominum.com]

> 
> On Wed, May 30, 2001 at 02:26:26PM -0400, Fabiola Caceres wrote:
> > 
> > Hi
> > is there any difference in doing:
> > 
> > $TTL    86400
> > @       IN      SOA ns1.infi.net. hostmaster.infi.net.
> > rest of zone file goes here...
> > 
> > ------------------
> > OR
> > 
> > @ 86400 IN      SOA ns1.infi.net. hostmaster.infi.net.
> > (
> >         2001051602      ; Serial
> >         10800           ; Refresh after 3 hours
> >         3600            ; Retry after 1 hour
> >         604800          ; Expire after 1 week
> >         86400           ; Minimum TTL of 1 day
> > )
> >         IN      NS      ns1.infi.net.
> >         IN      NS      ns2.infi.net.
> >         IN      NS      ns3.infi.net.
> >         IN      NS      ns4.infi.net.
> >         IN      A       216.33.107.214
> > www     IN      CNAME   vh50003.vh5.infi.net.
> > web     IN      CNAME   vh50003.vh5.infi.net.
> 
> Absolutely.
> 
> The first (a) is legal, and (b) establishes a default TTL for all
> records that follow.
> 
> The second is not legal, because no default TTL has been established,
> and all records after the SOA have no established TTL.  BIND 8.2ff will
> give a warning, and use the negative TTL [labeled as "minimum", above]
> as the value for the default positive TTL.  BIND 9 will object and not
> accept it.
> 
> Capish?
> 
> -- 
> Joe Yao				jsdy at cospo.osis.gov - Joseph S. D. Yao
> OSIS Center Computer Support					EMT-B
> -----------------------------------------------------------------------
> This message is not an official statement of COSPO policies.
> 

	Actually both are legal (provided you fix the SOA records in
	both examples to be legal).

	The first is using RFC2308 sematics to set TTLs on records
	without TTLs.  i.e. Inherited from previous $TTL.
	
	The second is using RFC103[45] sematics to set TTLs on records
	without TTLs.  i.e. Inherited from previous record.

	BIND 9 implements both starts in RFC103[45] mode and switches
	to RFC2308 mode when it reads a $TTL directive.
	
	BIND 8 behaves as if there was an implicit $TTL <minumum value>
	if there is not a explicit $TTL.

	Mark
--
Mark Andrews, Nominum Inc.
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at nominum.com