Primary DNS Server for Subnet.

Primary DNS Server for Subnet.

Post by Kyler Jones Hannigan engineering L » Sat, 05 Dec 1998 04:00:00



Can this be done?

If I have only a subnet, say, a handful of IP's alotted for my
lan from my ISP, can I run DNS for that subnet (not just caching, but
be the master for that zone)?

I think I know how to set it up, and I'm pretty sure I can have it
work for normal ip to name translation, but what about reverse lookups?

It seems to me that the reverse lookup zone entry in a bind8.* named.conf
file has to be something like:

        192.168.0.in-addr.arpa ...

(Insert real IP's for the local IP's).

Now, doesn't this mean that I am trying to control the reverse lookups
for the entire 192.168.0 domain even if I've only been give a a small
block of addresses in that range?

Does it matter?

Thanks in advance.

Kyler Jones

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Primary DNS Server for Subnet.

Post by Brian McCaule » Sat, 05 Dec 1998 04:00:00



Quote:> Can this be done?

Yes, but what has this got to do with Linux?  DNS has it's own
newsgroups you know.

Quote:> If I have only a subnet, say, a handful of IP's alotted for my
> lan from my ISP, can I run DNS for that subnet (not just caching, but
> be the master for that zone)?

Yes.  Do you have a fast, reliable, permanent connection?  If not then
you'll probably want all your published nameservers to be outside of
your LAN.  There's no need for your SOA server (master) to be
permanently connected just so long as it's up most of the time so that
the slaves can get updated.

Quote:> I think I know how to set it up, and I'm pretty sure I can have it
> work for normal ip to name translation, but what about reverse lookups?

> It seems to me that the reverse lookup zone entry in a bind8.* named.conf
> file has to be something like:

>    192.168.0.in-addr.arpa ...

> (Insert real IP's for the local IP's).

You mean 0.168.192.in-addr.arpa

Quote:> Now, doesn't this mean that I am trying to control the reverse lookups
> for the entire 192.168.0 domain even if I've only been give a a small
> block of addresses in that range?

Yes.

Quote:> Does it matter?

Yes.  If you have been delegated DNS control of a range of addresses less
than a class C then you need to see RFC2317 "Classless IN-ADDR.ARPA
delegation."

The exact details of implementation seem to vary.  Suppose your ISP
delegated you the following a subnet:

     192.168.0.64 - 192.168.0.95
aka  192.168.0.64-95
aka  192.168.0.54/255.255.255.224
aka  192.168.0.54/26

Then depending on how your IP was feeling you may find your zone is
named:

   64/26.0.168.192.in-addr.arpa
or 64.0.168.192.in-addr.arpa
or 64-95.0.168.192.in-addr.arpa
or anything-else-your-ISP-fancied.0.168.192.in-addr.arpa

For efficiency's sake you'd also probably want to make your DNS server
a notified slealth slave for the zone 0.168.192.in-addr.arpa if your
ISP will allow.

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Primary DNS Server for Subnet.

Post by Don Hannigan Hannigan engineering L » Sat, 05 Dec 1998 04:00:00



: > Can this be done?

: Yes, but what has this got to do with Linux?  DNS has it's own
: newsgroups you know.

I like in here.  Does this bother anyone.  I won't post here if it does.
I usually find linux users are hugely more responsive than general unix
paople.  Actually, you seem to respond to alot of the more technical
stuff.  Sorry if I've offended anyone by posting in here.

: > If I have only a subnet, say, a handful of IP's alotted for my
: > lan from my ISP, can I run DNS for that subnet (not just caching, but
: > be the master for that zone)?

: Yes.  Do you have a fast, reliable, permanent connection?  If not then
: you'll probably want all your published nameservers to be outside of
: your LAN.  There's no need for your SOA server (master) to be
: permanently connected just so long as it's up most of the time so that
: the slaves can get updated.

I actually do have a pretty good connection.  But for the moment, I'm just
trying to learn.  I love this stuff.

: > I think I know how to set it up, and I'm pretty sure I can have it
: > work for normal ip to name translation, but what about reverse lookups?
: >
: > It seems to me that the reverse lookup zone entry in a bind8.* named.conf
: > file has to be something like:
: >
: >  192.168.0.in-addr.arpa ...
: >
: > (Insert real IP's for the local IP's).

: You mean 0.168.192.in-addr.arpa

Sorry.

: > Now, doesn't this mean that I am trying to control the reverse lookups
: > for the entire 192.168.0 domain even if I've only been give a a small
: > block of addresses in that range?

: Yes.

: > Does it matter?

: Yes.  If you have been delegated DNS control of a range of addresses less
: than a class C then you need to see RFC2317 "Classless IN-ADDR.ARPA
: delegation."

: The exact details of implementation seem to vary.  Suppose your ISP
: delegated you the following a subnet:

:      192.168.0.64 - 192.168.0.95
: aka  192.168.0.64-95
: aka  192.168.0.54/255.255.255.224
: aka  192.168.0.54/26

: Then depending on how your IP was feeling you may find your zone is
: named:

:    64/26.0.168.192.in-addr.arpa
: or 64.0.168.192.in-addr.arpa
: or 64-95.0.168.192.in-addr.arpa
: or anything-else-your-ISP-fancied.0.168.192.in-addr.arpa

Is this something new that's allowed in RFC2317?  I just read through the
linux NAG and it said that DNS zones have to have netmask's that have on
byte boundaries and can't be subnets.

Sorry, just a couple more questions:

What would the consequences be if I did use 0.168.192.in-addr.arpa for my
reverse lookup zone?  Doesn't this only get queried when an outside
machine determined that it is looking for a hostname in my range?  So how
could it affect the other subnets in my range?

Also, and this one is a real newbie question, do I need to be pointed to
by my ISP's DNS setup for queries to reach my DNS server?

I really appreciate the help.
Thank you.

Kyler Jones

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