1
00:00:00,06 --> 00:00:04,04
- [Voiceover] Let's set up an Ubuntu host as a router.

2
00:00:04,04 --> 00:00:06,06
I'm assuming that you already have

3
00:00:06,06 --> 00:00:10,01
a second network interface card or NECs installed

4
00:00:10,01 --> 00:00:15,06
on your host either physically or virtually.

5
00:00:15,06 --> 00:00:20,02
Let me open a terminal and see if we have two NECs

6
00:00:20,02 --> 00:00:25,05
please note that this is our Ubuntu router VM

7
00:00:25,05 --> 00:00:36,05
Type ifconfig, press enter.

8
00:00:36,05 --> 00:00:41,02
The output shows eth0 and eth1

9
00:00:41,02 --> 00:00:44,06
which are the network interfaces.

10
00:00:44,06 --> 00:00:48,01
Eth0 and one are shorthands

11
00:00:48,01 --> 00:00:53,03
for ethernet cards zero and one which is the same as saying

12
00:00:53,03 --> 00:00:56,08
network interface card zero and one

13
00:00:56,08 --> 00:00:59,02
or NECs zero and one.

14
00:00:59,02 --> 00:01:02,09
Ethernet refers to a set of technical standards

15
00:01:02,09 --> 00:01:06,07
on local area networks or LANs.

16
00:01:06,07 --> 00:01:10,07
It specifies standards for NECs too

17
00:01:10,07 --> 00:01:15,03
and we often call a network interface card or NEC

18
00:01:15,03 --> 00:01:19,05
an ethernet card because of this reason.

19
00:01:19,05 --> 00:01:23,05
By the way the network addresses starting with 10

20
00:01:23,05 --> 00:01:26,03
we're using here is private.

21
00:01:26,03 --> 00:01:30,02
We use these addresses only within a local area network

22
00:01:30,02 --> 00:01:35,03
or LAN, which are never used as internet addresses.

23
00:01:35,03 --> 00:01:38,01
Another group of popular private addresses

24
00:01:38,01 --> 00:01:43,00
start with 192.168.

25
00:01:43,00 --> 00:01:49,08
Eth0 has an IP address of 10.0.0.6.

26
00:01:49,08 --> 00:01:55,02
The prefix inet here stands for internet.

27
00:01:55,02 --> 00:02:02,07
Eth1 has an IP address of 10.0.1.4.

28
00:02:02,07 --> 00:02:07,04
To turn our Ubuntu virtual machine or VM into a router

29
00:02:07,04 --> 00:02:12,07
we have to ensure eth0 belongs to one network

30
00:02:12,07 --> 00:02:17,00
while eth1 belongs to another.

31
00:02:17,00 --> 00:02:19,08
The network address of eth1

32
00:02:19,08 --> 00:02:22,08
looks slightly different from eth0

33
00:02:22,08 --> 00:02:27,07
because it belongs to another network or sub-net.

34
00:02:27,07 --> 00:02:35,04
In our example, the subnet mask is 255.255.255.0

35
00:02:35,04 --> 00:02:38,02
which means that we use the first three digits

36
00:02:38,02 --> 00:02:41,06
of an IP address as our subnet ID.

37
00:02:41,06 --> 00:02:48,07
Therefore 10.0.0 is a subnet ID of 10.0.0.6

38
00:02:48,07 --> 00:02:55,01
and 10.0.1 is a subnet ID of 10.0.1.4

39
00:02:55,01 --> 00:03:00,06
and they belong to different networks or subnets.

40
00:03:00,06 --> 00:03:04,06
Subnet here refers to a subdivided network.

41
00:03:04,06 --> 00:03:08,04
We divided our local area network into two here.

42
00:03:08,04 --> 00:03:15,01
One is 10 10.0.0 and the other is 10.0.1.

43
00:03:15,01 --> 00:03:21,00
I'm using Microsoft Azure to provision my VMs.

44
00:03:21,00 --> 00:03:28,03
I had to manually create the two subnets 10.0.0 and 10.0.1

45
00:03:28,03 --> 00:03:32,04
and associate them with eth0 and eth1

46
00:03:32,04 --> 00:03:36,01
respectively in my virtual network.

47
00:03:36,01 --> 00:03:41,09
Azure automatically configured my second NEC or eth1.

48
00:03:41,09 --> 00:03:43,05
Excellent job.

49
00:03:43,05 --> 00:03:46,03
You're now well on your way to the next step

50
00:03:46,03 --> 00:03:49,00
of setting up your Ubuntu to host as a router.