 Here we have three Linux machines set up in virtual box a client a router and a server Let's learn a little bit about some Linux network in command starting with I have conflict my virtual network or my Network between those Linux machines inside virtual box is shown in this picture where the client and the router on some virtual LAN net a the router and server on a separate LAN net B and They've been set up and that IP addresses are allocated to different interfaces There's also a net interface on each of those Linux machines so that they have real internet access via virtual box and by my real PC so let's look at the client first and We'll use I have conflict to see information about my interface configuration So my network interface configuration when we run I have config on its own. It shows me the list of Interfaces which are enabled or or turned on or referred to by I have config is up up and running and It shows there are three ENP zero s3 ENP zero s8 and LO loopback interface if we just Change the font to be a little bit larger We can see that in a bit more depth And we can scroll through so For each interface I have config shows us some information about that interface And we'll look at one of those in depth in a moment We can pass in one of the interface names as an option. I Have conflict ENP zero s8. I know that exists and it shows me the details for that interface So what does it tell me? We'll go through some of this information. It tells me this is an ethernet interface It has a hardware address or a MAC address of this particular value and Since we're using virtual box that is actually assigned by virtual box in a real Computer that would be the the address assigned to your Mac or your LAN card We have an IPv4 address an internet address 192 168 1.11 and Associated broadcast address and network mask for that IPv4 address In my case, these were set up when the machine booted from a different location We can also manually set them using I have config and other processes Have an IPv6 address Although it's not a global address. It's a link local address and that's been allocated automatically We're not going to touch IPv6 at this stage. We will add a later stage a Bit of information about the status of the interface. It is up up means it's it's turned on its running It supports broadcast multicast and has a maximum transmission unit of 1500 bytes Some statistics about how many packets have been received and transmitted on this interface Collisions a queue length and the bytes received and transmitted So some basic information about your interface and some statistics can be obtained using I have config When we run I have config it shows all up interfaces In the man page I have config. It's got several options And we can read through one of them will use commonly as minus a so I Have config minus a shows us all interfaces those that are up and also down now in this case it is No different all of my interfaces are actually up But if there were some interfaces which were not up which were down Then they would be shown when we use I have config minus a So we can use I have config to show interface configuration We can also use it to change interface configuration For example, we can turn an interface Up or down just clear that I have config EMP 0s 8 is my one of my interfaces if I want to turn it down. I can type the option come up down Noting that if we want to make changes to the network configuration, we'd need to have administrator rights So I'll proceed that with Sudo and Ask for my password which I have and now I run I have config It lists EMP 0s 3 which is up my loop back interface which is up and it doesn't list EMP 0s 8 It's down if I add the minus a option all it does include EMP 0s 8 And it's not listed as up and running here. Whereas the first one was up here We don't list up so EMP S EMP 0s 8 is down. It's not turned on. We cannot use it We turn it back up As you may guess It's now up and running So we can turn an interface off if we don't need it And turn it back on if it wasn't originally off you can also Make changes to the addresses used by the interface. I'm currently using the address 192.168.1.11 We can change the interface configuration of EMP 0s 8 and We can set the address Let's say 1.12 and I should specify the net mask and it's good practice when you change the address to make sure the interface is up It's not needed, but I'll include it at the end to say let's If it was down before let's turn it up. If it was up before then it makes no difference And we know that we've now changed the IP address of that interface So we can change the configuration of the interface using IF config as well as view basic information We will see if we go to our router It's just another quick example I have config on the router Quite simply it shows us that we have three ethernet interfaces the NAT interface and Then it's because it's a router on network A and network B. It has EMP 0s 8 and EMP 0s 9 and different IP addresses and the loopback interface is for testing purposes normally for communicating with yourself to send yourself with the local loopback address of 127.0.0.1 So I have config is a quick way to view interface information and to make changes to the IP address for your interface