Debian Router - Dhcp Server Setup

We''ve learned previously how to set up unbound dns server as caching dns server for our LAN users, in this article we''ll configure dhcp server from which a unique ip address for each client assigned as a bonus automatically configure dns server settings for them.

We need to tell isc-dhcp-server where to listen and serve dhcp request, to do that we modify /etc/default/isc-dhcp-server as follows:

Our LAN is on eth1 so set

INTERFACESv4="eth1"

the whole file will look like:

# Defaults for isc-dhcp-server (sourced by /etc/init.d/isc-dhcp-server)

# Path to dhcpd''s config file (default: /etc/dhcp/dhcpd.conf).
#DHCPDv4_CONF=/etc/dhcp/dhcpd.conf
#DHCPDv6_CONF=/etc/dhcp/dhcpd6.conf

# Path to dhcpd''s PID file (default: /var/run/dhcpd.pid).
#DHCPDv4_PID=/var/run/dhcpd.pid
#DHCPDv6_PID=/var/run/dhcpd6.pid

# Additional options to start dhcpd with.
#	Don''t use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
#OPTIONS=""

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
#	Separate multiple interfaces with spaces, e.g. "eth0 eth1".
INTERFACESv4="eth1"
INTERFACESv6=""

authoritative;

######################
# internal network
######################
subnet 10.5.5.0 netmask 255.255.255.0 {
 range 10.5.5.6 10.5.5.254;
 option domain-name-servers 10.5.5.1;
 option routers 10.5.5.1;
 option broadcast-address 10.5.5.255;
 default-lease-time 600;
 max-lease-time 7200;
}

Give LAN-AP a fixed ip address, this address must not be available for dynamiclly assigned ip addresses range, notice that we''ve already chosen 10.5.5.5 which is out of the range  [10.5.5.6 - 10.5.5.254]

replace 00:00:00:00:00:00 with your LAN-AP mac address:

# LAN-AP need fixed ip address 10.5.5.5
# 00:00:00:00:00:00 mustbe replaces with router hardware mac address
host router{
 hardware ethernet 00:00:00:00:00:00;
 fixed-address 10.5.5.5;
}

# The ddns-updates-style parameter controls whether or not the server will
# attempt to do a DNS update when a lease is confirmed. We default to the
# behavior of the version 2 packages (''none'', since DHCP v2 didn''t
# have support for DDNS.)
ddns-update-style none;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
authoritative;

######################
# internal network
######################
subnet 10.5.5.0 netmask 255.255.255.0 {
 range 10.5.5.6 10.5.5.254;
 option domain-name-servers 10.5.5.1;
 option routers 10.5.5.1;
 option broadcast-address 10.5.5.255;
 default-lease-time 600;
 max-lease-time 7200;
}

# LAN-AP need fixed ip address 10.5.5.5
# 00:00:00:00:00:00 mustbe replaces with router hardware mac address
host router{
 hardware ethernet 00:00:00:00:00:00;
 fixed-address 10.5.5.5;
}

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