L'internet rapide et permanent

Outils pour utilisateurs

Outils du site

Vous êtes ici : L'internet rapide et permanent » Les protocoles applicatifs » DHCP » Le client DHCP d'ISC

Table des matières

Le client DHCP d'ISC

Sur Debian 12 (Bookworm), le client dhcp installé par défaut est le client d'isc: isc-dhcp-client. Ce client dispose d'un fichier de configuration /etc/dhcp/dhclient.conf. Comparons les configurations sur «nas» et «democlient1»

Configuration

nas

Version expurgée des commentaires: 

option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;

send host-name = gethostname();
request subnet-mask, broadcast-address, time-offset, routers,
        domain-name, domain-name-servers, domain-search, host-name,
        dhcp6.name-servers, dhcp6.domain-search, dhcp6.fqdn, dhcp6.sntp-servers,
        netbios-name-servers, netbios-scope, interface-mtu,
        rfc3442-classless-static-routes, ntp-servers;
Ce fichier n'a pas été modifié, c'est donc la configuration par défaut.

Toutes les options en gras sont inutiles dans notre contexte. Elles ont été supprimées dans le fichier de configuration sur «democlient1»

democlient1

option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;

send host-name = gethostname();
request subnet-mask, broadcast-address, time-offset, routers,
        domain-name, domain-name-servers, domain-search,
        rfc3442-classless-static-routes, ntp-servers;

send dhcp-client-identifier 1:52:54:00:b7:66:81;
En revanche, ici le client envoie explicitement sa seule adresse MAC comme CID, ce qui explique l'apparente anomalie constatée page précédente.

La mémoire du client

isc-dhcp-client a de la mémoire. Elle est écrite dans le fichier /var/lib/dhcp/dhclient.enp1s0.leases. Voyons la mémoire du nas: 

cat dhclient.enp1s0.leases 
default-duid "\000\001\000\001/qNjRT\000\322\232\016";
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 11:04:54;
  rebind 6 2025/03/22 11:20:11;
  expire 6 2025/03/22 11:35:11;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 11:29:41;
  rebind 6 2025/03/22 11:49:54;
  expire 6 2025/03/22 12:04:54;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 11:54:35;
  rebind 6 2025/03/22 12:14:41;
  expire 6 2025/03/22 12:29:41;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 12:21:31;
  rebind 6 2025/03/22 12:39:35;
  expire 6 2025/03/22 12:54:35;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 12:46:46;
  rebind 6 2025/03/22 13:06:31;
  expire 6 2025/03/22 13:21:31;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 13:14:36;
  rebind 6 2025/03/22 13:31:46;
  expire 6 2025/03/22 13:46:46;
}
Le serveur était hors service et le client a perdu son adresse, mais il l'a récupérée aux alentours de 14:18:47 - 30 minutes soit 13:48:47. L'interruption a été de courte durée. 
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 14:18:47;
  rebind 6 2025/03/22 14:38:28;
  expire 6 2025/03/22 14:53:28;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 14:48:17;
  rebind 6 2025/03/22 15:03:47;
  expire 6 2025/03/22 15:18:47;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 15:13:52;
  rebind 6 2025/03/22 15:33:17;
  expire 6 2025/03/22 15:48:17;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 15:40:37;
  rebind 6 2025/03/22 15:58:52;
  expire 6 2025/03/22 16:13:52;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 16:06:35;
  rebind 6 2025/03/22 16:25:37;
  expire 6 2025/03/22 16:40:37;
}
lease {
  interface "enp1s0";
  fixed-address 192.168.61.2;
  option subnet-mask 255.255.255.0;
  option dhcp-lease-time 3600;
  option routers 192.168.61.1;
  option dhcp-message-type 5;
  option dhcp-server-identifier 192.168.61.1;
  option domain-name-servers 192.168.61.1;
  option domain-search "home.nain-t.net.";
  option dhcp-renewal-time 1800;
  option dhcp-rebinding-time 2700;
  option host-name "nas";
  option dhcp-client-identifier ff:0:d2:9a:e:0:1:0:1:2f:71:4e:6a:52:54:0:d2:9a:e;
  renew 6 2025/03/22 16:29:12;
  rebind 6 2025/03/22 16:51:35;
  expire 6 2025/03/22 17:06:35;
}
Le client garde donc en mémoire les baux qu'il a récupéré dans le passé proche.

Le client DHCP d'ISC: Dernière modification le: 23/03/2025 à 09:40 par prof