5. Demo: LAN inside a Linux machine (IP address via DHCP server)

Topology

Expected result:

• All PCs can get an IP address from DHCP server
• All PCs can see each other
• All PCs can access Internet 

Configuration

sudo ip netns add pc1 sudo ip netns add pc2 sudo ip netns add pc3 sudo ip netns add pc4 sudo brctl addbr vSwitch sudo ip link add eth1 type veth peer name eth5 sudo ip link add eth2 type veth peer name eth6 sudo ip link add eth3 type veth peer name eth7 sudo ip link add eth4 type veth peer name eth8    sudo ip link set eth1 netns pc1 sudo ip link set eth2 netns pc2 sudo ip link set eth3 netns pc3 sudo ip link set eth4 netns pc4 sudo brctl addif vSwitch eth5 sudo brctl addif vSwitch eth6 sudo brctl addif vSwitch eth7 sudo brctl addif vSwitch eth8 #Set IP address for vSwitch interface sudo ip link set vSwitch up sudo ip addr add 10.0.0.1/24 dev vSwitch sudo ip link set eth5 up sudo ip link set eth6 up sudo ip link set eth7 up sudo ip link set eth8 up sudo ip netns exec pc1 ip link set eth1 up sudo ip netns exec pc2 ip link set eth2 up sudo ip netns exec pc3 ip link set eth3 up sudo ip netns exec pc4 ip link set eth4 up #Set forwarding route for host machine sudo bash -c 'echo 1 > /proc/sys/net/ipv4/ip_forward' sudo iptables -t nat -A POSTROUTING -o eth0 -j  MASQUERADE #Setup and configure DHCP server sudo apt-get install isc-dhcp-server #Edit these files as the below result sudo vi /etc/default/isc-dhcp-server sudo vi cat /etc/dhcp/dhcpd.conf sudo service isc-dhcp-server restart #Get IP address from DHCP server sudo ip netns exec pc1 dhclient -nw -v eth1 sudo ip netns exec pc2 dhclient -nw -v eth2 sudo ip netns exec pc3 dhclient -nw -v eth3 sudo ip netns exec pc4 dhclient -nw -v eth4 #Check Result sudo ip netns exec pc1 ping 8.8.8.8 sudo ip netns exec pc2 ping 8.8.8.8 sudo ip netns exec pc3 ping 8.8.8.8 sudo ip netns exec pc4 ping 8.8.8.8

Result

vdkmai@Ubuntu32bit:~$ cat /etc/default/isc-dhcp-server # Defaults for dhcp initscript # sourced by /etc/init.d/dhcp # installed at /etc/default/isc-dhcp-server by the maintainer scripts # # This is a POSIX shell fragment # # On what interfaces should the DHCP server (dhcpd) serve DHCP requests? #       Separate multiple interfaces with spaces, e.g. "eth0 eth1". INTERFACES="vSwitch" vdkmai@Ubuntu32bit:~$ cat /etc/dhcp/dhcpd.conf log-facility local7; default-lease-time 600; max-lease-time 7200; subnet 10.0.0.0 netmask 255.255.255.0 {   range 10.0.0.101 10.0.0.253;   option subnet-mask 255.255.255.0;   option routers 10.0.0.1;   option domain-name-servers 8.8.8.8; } vdkmai@Ubuntu32bit:~$ sudo ip netns exec pc4 dhclient -nw -v eth4 Internet Systems Consortium DHCP Client 4.1-ESV-R4 Copyright 2004-2011 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Listening on LPF/eth4/7a:56:5c:45:0f:7e Sending on   LPF/eth4/7a:56:5c:45:0f:7e Sending on   Socket/fallback DHCPREQUEST of 10.0.0.104 on eth4 to 255.255.255.255 port 67 vdkmai@Ubuntu32bit:~$ sudo ip netns exec pc4 ping 8.8.8.8 PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data. 64 bytes from 8.8.8.8: icmp_req=1 ttl=52 time=33.1 ms --- 8.8.8.8 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 33.184/33.184/33.184/0.000 ms vdkmai@Ubuntu32bit:~$ sudo ip netns exec pc4 ifconfig eth4      Link encap:Ethernet  HWaddr 7a:56:5c:45:0f:7e            inet addr:10.0.0.104  Bcast:10.0.0.255  Mask:255.255.255.0           inet6 addr: fe80::7856:5cff:fe45:f7e/64 Scope:Link           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1           RX packets:138 errors:0 dropped:0 overruns:0 frame:0           TX packets:16 errors:0 dropped:0 overruns:0 carrier:0           collisions:0 txqueuelen:1000           RX bytes:17281 (17.2 KB)  TX bytes:1960 (1.9 KB) vdkmai@Ubuntu32bit:~$ sudo ip netns exec pc4 ip route default via 10.0.0.1 dev eth4 10.0.0.0/24 dev eth4  proto kernel  scope link  src 10.0.0.104 vdkmai@Ubuntu32bit:~$ sudo ip netns exec pc4 traceroute 8.8.8.8 traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets  1  10.0.0.1 (10.0.0.1)  0.055 ms  0.012 ms  0.011 ms  2  * * *  3  * * *  4  * * *  5  * 59.12.187.1 (59.12.187.1)  5.185 ms  5.170 ms

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