DISCUSSION: Setting up DNS in Small Subnets

sgrayban · 01-23-2005, 08:47 PM

This thread is to discuss the article titled: Setting up DNS in Small Subnets

AndeAnderson · 10-04-2005, 12:10 PM

I had hoped this would help me to understand DNS set-ups.

But, it is started off with "If you try to run an authoritative DNS server for a small network, such as a /26." This sentence does not mean anything to me. what is "a /26" for a network? The added (which contains only 2(32-26)=64 addresses) just added to my confusion. Is that supposed to be a mathmatical statement?

Then, to explain the sample, this sentence finished me off, "In this example, we have a subnet mask of 255.255.255.192 (which is a /26 because the first 26 bits in the mask are 1's). The network's name is therefore 63.127.146.192/26."

Where did this subnet mask come from?

Thanks,

sgrayban · 10-04-2005, 07:33 PM

You can get the subnet mask from almost anyplace on the net -- try googling for "subnet mask calc"

AndeAnderson · 10-05-2005, 06:39 AM

Thanks Scott,

The more I get into Linux the more I wish I had stayed with Unix instead of going MS for Consulting and Customer Support. After about 10 years I am having to relearn a lot of basic information which I did not need to use with MS products.

sgrayban · 10-05-2005, 06:42 AM

Linux "teaches" how to be a network admin. Windows does not which is a shame.

flashingcurser · 10-01-2007, 03:03 PM

One thing I must mention. I have had dns admins look over some of my zone files and have gotten a royal chewing out for some things I see in this zone file.

Code:

@ IN SOA malaria.borgnet.us. hostmaster.borgnet.us. (
00000005; Serial Number (not a date)
21600   ; Refresh every 6 hours
3600    ; Retry every hour
1728000 ; Expire every 20 days
21600 ) ; Minimum 6 hours
IN NS malaria.borgnet.us.
IN MX 10 engram.borgnet.us.
IN A 63.127.146.236

The NS and MX records shouldn't give away the real hostname of the computer running it.

For example:

Code:

IN NS ns0.borgnet.us.
.borgnet.us. IN A 63.127.146.236
ns0 IN A 63.127.146.236 ; IP of the nameserver

In this case there is an "A" record to define where ns0 is and you point your ISP or registrar towards ns0 at the IP 63.127.146.236 This will give glue between the two yet not give away your host name "malaria". The same is true of MX.

Code:

IN MX 10 mail0.borgnet.us.
mail0 IN A XXX.XXX.XXX.XXX ; IP of the mail server

The least I can do is save someone from some of the ass-chewings that I received.