--- title: "DHCP Server and Routing" visible: true --- [toc] ## Installation [shroot] ```sh apt install isc-dhcp-server ``` [/shroot] ## Configuration Edit `/etc/default/isc-dhcp-server` ``` INTERFACESv4="[INTERFACE 1] [INTERFACE 2]" ``` Edit `/etc/dhcp/dhcpd.conf` to set a subnet ``` subnet [NETADDRESS] netmask [SUBNETMASK] { range [FIRST DHCP] [LAST DHCP]; option subnet-mask [SUBNETMASK]; option routers [GATEWAY]; option domain-name "[NAME]"; option domain-name-servers [DNS SERVER]; } ``` Edit `/etc/network/interfaces` ``` auto [INTERFACE] iface [INTERFACE] inet static address [ADDRESS] network [NETADDRESS] netmask [NETMASK] broadcast [BROADCAST] ``` Enable the interface [shroot] ```sh ifup [INTERFACE] ``` [/shroot] Restart DHCP Server [shroot] ```sh systemctl restart isc-dhcp-server.service ``` [/shroot] ### Enable routing [shroot] ```sh echo "net.ipv4.ip_forward=1" >> /etc/sysctl.d/80-forwarding.conf sysctl -p /etc/sysctl.d/80-forwarding.conf ``` [/shroot] [shroot] ```sh iptables -t nat -A POSTROUTING -o [WAN INTERFACE] -j MASQUERADE iptables -A FORWARD -i [LAN INTERFACE] -j ACCEPT ``` [/shroot] Make iptables permanent Select `Yes` during the installation to save current rules [shroot] ```sh apt install iptables-persistent ``` [/shroot] ### Enable DHCP-managed fixed IP address ``` host [HOSTNAME] { hardware ethernet [MAC ADDRESS]; fixed-address [IP ADDRESS]; } ``` ### Dynamic DNS _Needs a supported DNS like BIND or PowerDNS_ [Configure your DNS server to accept updates](/linux/services/powerdns) Add the following snippet to your `/etc/dhcp/dhcpd.conf` file How to generate the key is also described in the DNS article ``` ddns-updates on; ddns-update-style interim; update-static-leases on; ddns-domainname "testpdns"; ddns-rev-domainname "in-addr.arpa."; key "[KEYNAME]" { algorithm hmac-md5; secret "[KEY]"; }; zone testpdns { primary 127.0.0.1; key [KEYNAME]; } zone 7.168.192.in-addr.arpa. { primary 127.0.0.1; key [KEYNAME]; } ``` ## Client DHCP Request [shroot] ```sh dhclient -v ``` [/shroot] Release IP [shroot] ```sh dhclient -v -r ``` [/shroot]