Applying DNS to different subnets

Dissecting dhcpd.conf. Censored where appropriate (hopefully). Color-coded questions at bottom of post.

*PrivatePaste w/ Indentations here*

ddns-update-style interim;

ddns-domainname "dyn.company.com.";

key DHCP_COMPANY {

*omitted*

}

zone dyn.orderdis.com. {

primary XXX.XXX.0.50;

key DHCP_COMPANY;

}

zone XXX.XXX.in-addr.arpa. {

primary XXX.XXX.0.50;

key DHCP_COMPANY;

}

authoritative;

ddns-update-style interim;

deny duplicates;

authoritative;

default-lease-time 345600;

max-lease-time 691200;

option domain-name-servers XXX.XXX.0.50,XXX.XXX.255.250;

option netbios-name-servers XXX.XXX.0.50;

subnet XXX.XXX.0.0 netmask 255.255.0.0 {

one-lease-per-client on;

option broadcast-address XXX.XXX.255.255;

option domain-name "dyn.company.com";

option netbios-name-servers XXX.XXX.255.254;

option netbios-name-servers XXX.XXX.0.50;

option netbios-node-type 8;

option routers XXX.XXX.255.1;

option subnet-mask 255.0.0.0;

update-optimization on;

update-static-leases on;

class "Sayson480i" {

match if (substring(hardware,1,3) = 00:08:5d);

}

class "etherboot-an983" {

match if (substring(hardware,1,3) = 00:04:e2);

next-server XXX.XXX.255.254;

filename "nbi-2.6.0-thin1";

option root-path "/nfs/thin3";

}

class "etherboot-3c59x" {

match if (substring(hardware,1,3) = 00:01:02);

if substring (option vendor-class-identifier, 0, 9) = "PXEClient" {

next-server XXX.XXX.255.254;

filename "eb-5.2.2-3c905c-tpo.zpxe";

} else if substring (option vendor-class-identifier, 0, 9) = "PXEclient" {

next-server XXX.XXX.255.254;

filename "eb-5.2.2-3c905c-tpo.zpxe";

} else if substring (option vendor-class-identifier, 0, 9) = "Etherboot" {

next-server XXX.XXX.255.254;

filename "nbi-2.6.0-thin1";

option vendor-encapsulated-options 3c:09:45:74:68:65:72:62:6f:6f:74:ff;

} else {

next-server XXX.XXX.255.254;

option root-path "/nfs/thin2";

}

}

pool {

range XXX.XXX.2.0 XXX.XXX.2.254;

option domain-name-servers 208.67.222.123,208.67.220.123;

allow members of "etherboot-an983";

allow members of "etherboot-3c59x";

}

pool {

range XXX.XXX.3.0 XXX.XXX.3.254;

option domain-name-servers 208.67.222.123,208.67.220.123;

allow members of "Sayson480i";

}

pool {

range XXX.XXX.0.50 XXX.XXX.0.254;

option domain-name-servers 8.8.8.8,8.8.4.4;

deny unknown clients;

}

pool {

range XXX.XXX.1.50 XXX.XXX.1.112;

option domain-name-servers 208.67.222.123,208.67.220.123;

allow unknown clients;

}

}

subnet 127.0.0.0 netmask 255.255.255.0 {

}

host XXXXX1 {

hardware ethernet XX:XX:XX:XX:XX:XX;

option domain-name "company.com";

fixed-address XXX.XXX.0.45;

}

host XXXXX2 {

hardware ethernet XX:XX:XX:XX:XX:XX;

option domain-name "company.com";

fixed-address XXX.XXX.1.45;

}

host XXXXX3 {

hardware ethernet XX:XX:XX:XX:XX:XX;

option domain-name "company.com";

fixed-address XXX.XXX.2.45;

}

host XXXXX4 {

hardware ethernet XX:XX:XX:XX:XX:XX;

option domain-name "company.com";

fixed-address XXX.XXX.255.45;

}

1) What is this? What is it for and do?

2) What is this? What is it for and do?

3) Paying more attention to domain-name-servers, but what does this mean? Does it mean it applies to *EVERYTHING* -- literally all subnets and pools specified in this file?

4) And what is this? :?

5) I think here it gets specific about different subnets or ranges. Can I specify domain-name-servers for each range like I did here? Or would that be an invalid move?

If it is a valid move, then it should do something like this (as far as applying DNS to specified range):

* Apply DNS 208.67.222.123 and DNS 208.67.220.123 to XXX.XXX.2.0 through XXX.XXX.2.254, to XXX.XXX.3.0 through XXX.XXX.3.254, to XXX.XXX.1.50 through XXX.XXX.1.112

* Apply DNS 8.8.8.8 and DNS 8.8.4.4 to XXX.XXX.0.50 through XXX.XXX.0.254

Is this correct?

6) What is this little piece?