IPCONFIG Explained - Flush DNS Cache

hello everyone in this video we're going to talk about the ipconfig utility now this utility is a command line tool that displays the tcp ip network configuration for the network adapters on a windows computer it displays things like your ip address the subnet mask and the default gateway and it can also be used for a lot of other troubleshooting issues so let's go ahead and show an example of ipconfig for a computer so at a command prompt you just type in ipconfig and then you press enter so here is the basic network configuration for this computer so here is the ip address and this is an ipv4 address and this happens to be a private ip address that's been assigned to us by a dhcp server that's built into our router or modem router combo that's in our home or office and then here we have the subnet mask which defines which parts of the ip address refers to the network and which part refers to the host and then we have our default gateway now the default gateway is the ip address of the router or modem router combo in your home or small office that your computer connects to on your network so your default gateway device is what gives you access to or direct you to another network such as the internet now if you notice we also have another ip address assigned to our computer and this is an ipv6 address so here we see that our computer has been assigned two ip addresses it has an ipv4 address and an ip6 address and this is what's called a dual stack and the reason for a dual stack is for compatibility purposes because right now the internet is in the middle of a migration from ipv4 to ipv6 and this is because there is a limit of public ipv4 addresses and we are running out and ipv6 was created to remedy this problem and having dual stack connectivity allows your isp to process ipv4 and ipv6 data simultaneously and the reason for this is that so you won't have any compatibility issues when accessing websites and servers during the migration now just to clear things up this ipv4 address is not a public ip address that we are running low on this is a private ip address that's used for private networks it's the external public ip addresses that our isp has assigned us that we are running low on in fact if you go to whatsmyipaddress.com you'll see the ipv6 and the external public ipv4 address that our isp has assigned to our home or office now if your computer was directly connected to the internet by using a plain modem which is rare these days then you would see the external public ipv4 address in the ipconfig output but these days most people will have a router or a modem router combo that will assign your computer a private ip address now ipconfig can be combined with sub commands called switches and switches will give you more options so for example let's do the ipconfig command again and this time we're going to add a forward slash all at the end and then we'll press enter and as you can see this displays more information than just the basics so doing an ipconfig forward slash all command it'll display the full tcp configuration for your network adapters on your computer so in addition to showing us our ip address subnet mask and default gateway it also shows us other things such as the host name which is the custom name that we gave our computer it also shows us the physical address or mac address for our network adapter which is a unique identifier for every network adapter it also shows us that dhcp is enabled which means that our ip address is given to us by a dhcp server which is built into our router it also shows us the ip address of the dhcp server which happens to be the same as our default gateway which is the router and here it shows us the date and time of when we obtained the lease for our ip address along with its expiration and it also shows us the ip address of the dns server that our computer is using and ipconfig forward slash flush dns is another command now this tool is what flushes or clears the dns resolver cache on your computer dns or domain name system is used to resolve domain names to ip addresses so for example it's what turns a domain name such as youtube.com into an ip address and this has to happen because computers don't understand names they only understand numbers which is what an ip address is so that's why it has to be converted into a number so the computer can understand it and retrieve the web page now operating systems cache or keep a history of resolved domain names and their i p addresses that you visited and it keeps this record for a period of time and the reason for this cache is to make web browsing faster because when you want to visit a webpage such as youtube.com your computer doesn't have to constantly go out to an external dns server to resolve youtube.com to an ip address it can just look at its internal dns cache which is a lot quicker so instead of taking seconds to retrieve a web page it would only take milliseconds and in addition it frees up the dns server from constantly getting bombarded with dns lookups now even though caching these web addresses are a good thing there are some instances where you should flush your dns cache and one reason is is that if you're having a problem accessing certain websites so for example if youtube.com has changed their ip address and if your dns cache is still storing the old ip address then you won't be able to access youtube because the dns cache on your computer is outdated and flushing your dns can also help with security concerns such as dns spoofing now dns spoofing is when hackers and malware can alter your dns cache and redirect you to fraudulent websites and they can use this tactic to steal sensitive information so this is why you should flush your dns if you suspect that your dns cache has been maliciously altered and finally another benefit of flushing your dns cache is that it will help hide your website search behavior now if you wanted to see what is actually stored in your dns cache you can use our next command which is ipconfig forward slash display dns and this will display the contents of a dns resolver cache on your computer now normally this would show a bunch of records but in this example i'm only going to show you one dns record so this dns record is from youtube.com and over here you can see the time to live or ttl which is a number that limits the lifespan of this record so the ttl will count down and when it gets to zero the record will be erased and then here we see the ip address for youtube.com and as i said before if you wanted to empty the cache just use the flush command again and it will clear it and then if you display the dns again you'll see that the dns cache is empty so these are just a few switches that you can use with ipconfig but if you wanted to see the full list of switches that are available just type ipconfig forward slash and then a question mark so thank you everyone for watching please subscribe and i will see you in the next video you

Channel: PowerCert Animated Videos

Views: 115,541

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Keywords: ipconfig command, ipconfig release renew, ipconfig flushdns, flush dns command, network troubleshooting, command prompt, how to flush dns, flush dns, hacking dns, default gateway, dual stack

Id: ZKhorleA5aA

Length: 8min 54sec (534 seconds)

Published: Wed May 12 2021