Host Declaration

Jérôme BECOT jerome.becot at inalco.fr
Sat Sep 23 12:55:38 UTC 2017


I'd like to know if I declare the host group outside the subnet it would be the same as declaring them directly inside the subnet block. Isc doesn't complain both ways. 

If the client configuration would be the same, then what is the best way (best practice) to declare them (inside or outside the subnet) ? 


I think you have already answered saying host statments are global, but please confirm. 

Thank you 

JEROME BECOT 
Ingénieur Système et Réseau 
DSIRN 
Bureau n°4.29 
Institut national des langues et civilisations orientales 
65 rue des Grands Moulins 
Paris 75013, France 

01 81 70 10 78 
jerome.becot @inalco.fr 
[ http://www.inalco.fr/ | www.inalco.fr ] 


De: "Bill Shirley" <bill at c3po.polymerindustries.biz> 
À: "Users of ISC DHCP" <dhcp-users at lists.isc.org> 
Envoyé: Samedi 23 Septembre 2017 06:39:34 
Objet: Re: Host Declaration 

host statements are global. 

Example: 
subnet 10.10.10.0 netmask 255.255.255.0 { 
ddns-updates on; 
default-lease-time 3600; # 1 hour 
} 
group "storage" { 
ddns-updates off; 
option log-servers 10.10.10.1; 
host storage-1 { hardware ethernet ff:ca:ff:26:30:4b; fixed-address 10.10.10.4; } 
host storage-2 { hardware ethernet ff:ca:ff:26:30:4b; fixed-address 10.10.10.5; default-lease-time 7200; } 
} 

In the above example, host storage-1 will have 'ddns-updates off' and 'option log-servers 10.10.10.1' 
and a lease time of 3600 when allocated from the 10.10.10.0 subnet. 

Host storage-2 will have 'ddns-updates off' and 'option log-servers 10.10.10.1' and a lease time of 7200; 

What problem are you trying to solve? 

Bill 


On 9/22/2017 9:16 AM, Jérôme BECOT wrote: 



Hello everyone, 

I'm wondering about the difference between declaring hosts at the global level and in their respective subnets. It looks like the same to me but I may miss something about it. They would inherit the subnet parameters the same way, wouldn't it ? 

subnet 10.10.10.0/24 { 
option X value; 
host zero { .. } 
} 

group "site-A hosts" { 
host one { 10.10.10.1; } 
} 

.... 

Also, what happen if I declare a group of subnets and a separate group of hosts outside, like : 

group "site-B subnets" { 
option A value1; 
subnet 10.0.0.0/8{ ... } 
subnet 172.16.0.0./16 { ... } 
} 

group "site-B hosts" { 
host zero { fixed-address: 10.0.0.1; } 
} 

Is host 0 receiving the option A value as well ? 

Thanks 

JEROME BECOT 
Ingénieur Système et Réseau 
DSIRN 
Bureau n°4.29 
Institut national des langues et civilisations orientales 
65 rue des Grands Moulins 
Paris 75013, France 

01 81 70 10 78 
jerome.becot @inalco.fr [ http://www.inalco.fr/ | www.inalco.fr ] 


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