In this tutorial, i will show you how to create a simple network topology in your computer. For the first step, you need to install mininet on your computer.

Environment:

parallels@parallels-vm:~$ uname -r
4.13.0-43-generic
parallels@parallels-vm:~$ uname -a
Linux parallels-vm 4.13.0-43-generic #48~16.04.1-Ubuntu SMP Thu May 10 12:56:46 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
parallels@parallels-vm:~$ git clone git://github.com/mininet/mininet
parallels@parallels-vm:~$ cd mininet
parallels@parallels-vm:~$ util/install.sh -a

parallels@parallels-vm:~$ sudo mn -h
Usage: mn [options]
(type mn -h for details)

The mn utility creates Mininet network from the command line. It can create
parametrized topologies, invoke the Mininet CLI, and run tests.

Options:
  -h, --help            show this help message and exit
  --switch=SWITCH       default|ivs|lxbr|ovs|ovsbr|ovsk|user[,param=value...]
                        ovs=OVSSwitch default=OVSSwitch ovsk=OVSSwitch
                        lxbr=LinuxBridge user=UserSwitch ivs=IVSSwitch
                        ovsbr=OVSBridge
  --host=HOST           cfs|proc|rt[,param=value...]
                        rt=CPULimitedHost{'sched': 'rt'} proc=Host
                        cfs=CPULimitedHost{'sched': 'cfs'}
  --controller=CONTROLLER
                        default|none|nox|ovsc|ref|remote|ryu[,param=value...]
                        ovsc=OVSController none=NullController
                        remote=RemoteController default=DefaultController
                        nox=NOX ryu=Ryu ref=Controller
  --link=LINK           default|ovs|tc|tcu[,param=value...] default=Link
                        ovs=OVSLink tcu=TCULink tc=TCLink
  --topo=TOPO           linear|minimal|reversed|single|torus|tree[,param=value
                        ...] linear=LinearTopo torus=TorusTopo tree=TreeTopo
                        single=SingleSwitchTopo
                        reversed=SingleSwitchReversedTopo minimal=MinimalTopo
  -c, --clean           clean and exit
  --custom=CUSTOM       read custom classes or params from .py file(s)
  --test=TEST           none|build|all|iperf|pingpair|iperfudp|pingall
  -x, --xterms          spawn xterms for each node
  -i IPBASE, --ipbase=IPBASE
                        base IP address for hosts
  --mac                 automatically set host MACs
  --arp                 set all-pairs ARP entries
  -v VERBOSITY, --verbosity=VERBOSITY
                        info|warning|critical|error|debug|output
  --innamespace         sw and ctrl in namespace?
  --listenport=LISTENPORT
                        base port for passive switch listening
  --nolistenport        don't use passive listening port
  --pre=PRE             CLI script to run before tests
  --post=POST           CLI script to run after tests
  --pin                 pin hosts to CPU cores (requires --host cfs or --host
                        rt)
  --nat                 [option=val...] adds a NAT to the topology that
                        connects Mininet hosts to the physical network.
                        Warning: This may route any traffic on the machine
                        that uses Mininet's IP subnet into the Mininet
                        network. If you need to change Mininet's IP subnet,
                        see the --ipbase option.
  --version             prints the version and exits
  --cluster=server1,server2...
                        run on multiple servers (experimental!)
  --placement=block|random
                        node placement for --cluster (experimental!)

Ok! Let's start to create a realistic virtual network!

1.Create a simple network topology:

parallels@parallels-vm:~$ sudo mn
*** Creating network
*** Adding controller
*** Adding hosts:
h1 h2 
*** Adding switches:
s1 
*** Adding links:
(h1, s1) (h2, s1) 
*** Configuring hosts
h1 h2 
*** Starting controller
c0 
*** Starting 1 switches
s1 ...
*** Starting CLI:
mininet> 

2. Check how many nodes are in the network topology:

mininet> nodes
available nodes are: 
c0 h1 h2 s1

3.Check network topology connection status:

mininet> net
h1 h1-eth0:s1-eth1
h2 h2-eth0:s1-eth2
s1 lo:  s1-eth1:h1-eth0 s1-eth2:h2-eth0
c0

4.you can type a command to operate on special equipment:

mininet> h1 ifconfig
h1-eth0   Link encap:Ethernet  HWaddr e6:06:6d:77:e4:c5  
          inet addr:10.0.0.1  Bcast:10.255.255.255  Mask:255.0.0.0
          inet6 addr: fe80::e406:6dff:fe77:e4c5/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:59 errors:0 dropped:0 overruns:0 frame:0
          TX packets:31 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:5911 (5.9 KB)  TX bytes:2630 (2.6 KB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

5.Closed the mininet:

mininet> exit
*** Stopping 1 controllers
c0 
*** Stopping 2 links
..
*** Stopping 1 switches
s1 
*** Stopping 2 hosts
h1 h2 
*** Done
completed in 779.394 seconds

You can use sudo mn -c to clean the virtual network environment when something problems.