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Classless in-addr.arpa delegation

Classless in-addr.arpa delegation. Why . Many enterprises are joining the net Size frequently does not justify /24 prefix Desire to assign < /24 prefix Problem delegating in-addr.arpa authority because in-addr.arpa mechanism is octet-oriented. The problem.

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Classless in-addr.arpa delegation

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  1. Classless in-addr.arpa delegation

  2. Why • Many enterprises are joining the net • Size frequently does not justify /24 prefix • Desire to assign < /24 prefix • Problem delegating in-addr.arpa authority because in-addr.arpa mechanism is octet-oriented

  3. The problem • Enterprise A has 192.0.2.0/27 • Enterprise B has 192.0.2.32/28 • Who maintains 2.0.192.in-addr.arpa?

  4. Approach 1 • Have 2.0.192.in-addr.arpa maintained by central body (e.g. service provider) • Maintainer must be notified of every change • Delays in processing • Does not scale

  5. CNAME • CNAME can be used to ‘move’ objects in the DNS tree:www.foo.com CNAME server.isp.net • Can use CNAME to alias parts of in-addr tree

  6. Normal delegation $ORIGIN 2.0.192.in-addr.arpa.1 PTR pc1.other.domain.2 PTR pc2.other.domain....

  7. Approach 2 $ORIGIN 2.0.192.in-addr.arpa.0 CNAME 0.some.domain.1 CNAME 1.some.domain.2 CNAME 2.some.domain.… 32 CNAME 32.other.domain.33 CNAME 33.other.domain. $ORIGIN some.domain.1 PTR pc1.some.domain.

  8. Moving PTR records to different zones • Can point CNAME records to other places in domain tree: • in-addr.arpa.some.domain • 0/27.2.0.192.in-addr.arpa • 0-27.2.0.192.in-addr.arpa

  9. Comments • Need to add (a lot of) CNAME records in 2.0.192.in-addr.arpaThis is normal • This is not hard, it is confusing • domain names may be confusing

  10. Documentation • See RFC2317 for documentation(it’s not a tutorial, however) • See ‘DNS and BIND’ page 214 onwards

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