DHCP Relay and Server lab

This Labs show an example of IPv4 DHCP Relay and server with BSDRP

Presentation

Network diagram

Here is the logical and physical view:

Setting-up the lab

Downloading BSD Router Project images

Download a BSDRP serial image (prevent to have to use an X display) on SourceForge.

Downloading BSDRP lab scripts and starting the lab

More information on these BSDRP lab scripts available on How to build a BSDRP router lab.

Start a lab with 3 routers full meshed (no common LAN), example with VirtualBox script:

./BSDRP-lab-vbox.sh -n 3 -i BSDRP_0.36_full_amd64_serial.img

Routers configuration

Router 3 (DHCP server)

Edit the /etc/rc.conf file:

[root@router]~#vi /etc/rc.conf

And change these parameters:

hostname="R3.bsdrp.net"
#Routing not needed
gateway_enable="NO"
ipv6_gateway_enable="NO"
quagga_enable="NO"
ifconfig_em1="10.0.23.3/24"
defaultrouter="10.0.23.2" 
dhcpd_enable="YES"
dhcpd_flags="-q"
dhcpd_conf="/usr/local/etc/dhcpd.conf"
dhcpd_ifaces="em1"

Then Edit the DHCP server config file:

[root@router]~#vi /usr/local/etc/dhcpd.conf

And fill this file with theses parameters:

option domain-name "bsdrp.net";
default-lease-time 600;
max-lease-time 7200;
ddns-update-style none;
subnet 10.0.23.0 netmask 255.255.255.0 {
}

subnet 10.0.12.0 netmask 255.255.255.0 {
  range 10.0.12.100 10.0.12.200;
  option routers 10.0.12.2;
}

Then Apply the changes:

[root@router]~#hostname R3.bsdrp.net
[root@R3]~#/etc/rc.d/netif restart
[root@R3]~#/usr/local/etc/rc.d/isc-dhcpd start
[root@R3]~#config save

Router 2 (Router and DHCP Relay)

Edit the /etc/rc.conf:

[root@router]~#vi /etc/rc.conf

and set these parameters:

hostname="R2.bsdrp.net"
ifconfig_em0="10.0.12.2/24"
ifconfig_em1="10.0.23.2/24"
dhcrelay_enable="YES"
dhcrelay_servers="10.0.23.3"
dhcrelay_ifaces="em0 em1"

You must declare the interfaces where DHCP Request (from the DHCP clients) AND DHCP Reply (from the DHCP server) will be received

Then apply the changes:

[root@router]~#hostname R2.bsdrp.net
[root@R2]~#/etc/rc.d/netif restart
[root@R2]~#/usr/local/etc/rc.d/isc-dhcrelay start
Starting dhcrelay.
Internet Systems Consortium DHCP Relay Agent 4.2.2
Copyright 2004-2011 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Listening on BPF/em1/aa:aa:00:00:02:23
Sending on   BPF/em1/aa:aa:00:00:02:23
Listening on BPF/em0/aa:aa:00:00:02:12
Sending on   BPF/em0/aa:aa:00:00:02:12
Sending on   Socket/fallback
[root@R2]~#config save

Router 1 (DHCP client)

Edit the /etc/rc.conf:

[root@router]~#vi /etc/rc.conf

And set theses parmaters:

hostname="R1.bsdrp.net"
ifconfig_em0="DHCP"
# Disable routing
gateway_enable="NO"
ipv6_gateway_enable="NO"
quagga_enable="NO"

Then save the changes:

[root@router]~#hostname R1.bsdrp.net
[root@R1]~#config save

Final testing

Send a DHCP Discover from R1:

[root@R1]~#dhclient em0
DHCPDISCOVER on em0 to 255.255.255.255 port 67 interval 7
DHCPOFFER from 10.0.12.2
DHCPREQUEST on em0 to 255.255.255.255 port 67
DHCPACK from 10.0.12.2
bound to 10.0.12.100 -- renewal in 300 seconds.

Check that default route was received:

[root@R1]~#show route | grep default
default            10.0.12.2          UGS         0        4    em0

And ping the DHCP server:

[root@R1]~#ping 10.0.23.3
PING 10.0.23.3 (10.0.23.3): 56 data bytes
64 bytes from 10.0.23.3: icmp_seq=0 ttl=63 time=2.680 ms
64 bytes from 10.0.23.3: icmp_seq=1 ttl=63 time=1.190 ms
64 bytes from 10.0.23.3: icmp_seq=2 ttl=63 time=1.195 ms
^C
--- 10.0.23.3 ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 1.190/1.688/2.680/0.701 ms

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