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pages/02.linux/15.dhcp-server-and-routing/default.en.md

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+---
+title: 'DHCP Server and Routing'
+---
+
+## Installation
+`# apt install isc-dhcp-server`  
+
+## 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  
+`# ifup (interface)`  
+
+Restart DHCP Server  
+`# systemctl restart isc-dhcp-server.service`  
+
+### Enable routing
+`# echo "net.ipv4.ip_forward=1" >> /etc/sysctl.d/80-forwarding.conf`  
+`# sysctl -p /etc/sysctl.d/80-forwarding.conf`  
+
+`# iptables -t nat -A POSTROUTING -o (WAN interface) -j MASQUERADE`  
+`# iptables -A FORWARD -i (LAN interface) -j ACCEPT`  
+
+Make iptables permanent  
+Select `Yes` during the installation to save current rules  
+`# apt install iptables-persistent`  
+
+### Enable DHCP-managed fixed IP address
+```
+host (hostname) {
+  hardware ethernet (mac);
+  fixed-address (ip address);
+}
+```
+
+### Dynamic DNS
+*Needs a supported DNS like BIND or PowerDNS*  
+[Configure your DNS server to accept updates](https://wiki.realstickman.net/e/en/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  
+`# dhclient -v`  
+
+Release IP  
+`# dhclient -v -r`