DHCP and DNS July 2021 | Cisco CCNA 200-301

[Music] hello and welcome everybody thanks for being here for this game it's an updated version of dhcp and dns based on feedback from yesterday so thank you everybody for the office hour yesterday a lot of fun and thanks for the recommendations so i'm looking at the uh the chats and i see uh mahid and daniel and jama and iqbal and dar osuma fred tz blendinator welcome everybody michael's in the house asif ty's here adil's here ben's here here apology i apologize in advance for my accent ah thank you blending blending aka dan is saying good luck to everybody with a super sticker dan is dennis so dan you are so great on discord and here on the channel helping other people and i really enjoy your input so thanks for all the service you're giving to so many people [Music] hola alex grotham's here nick003 samson arn samson armstrong is here good to have everybody we're going to start here in just a few moments i get a little bit of late start today i had some company in town they're just leaving as we speak so i am all yours for the next 35 minutes for this live quiz 10 questions all the questions are about 60 seconds each for answering and then right afterwards we'll jump into the discord server if you have specific questions about any of these questions in the live stream join us in discord for a few minutes and we can just chat and elaborate on them to your heart's content [Music] [Applause] on summer and you're very welcome thank you for the feedback naomi's in the house from ethiopia welcome welcome and e angel states passed the exam two weeks ago thanks for your videos and sessions ah that's so great well e angel i'm so proud of you for putting in the work that's fantastic the foundation the fundamentals that we learn as part of ccna will serve us in networking for a long long time so congrats to everybody who's putting in the time and effort because it's not always comfortable it's not it's not always comfortable to study and learn however sometimes it can be super fun and it's going to be super beneficial for you all right dirtec it is in the house and aloahu has booked their exam for next friday serg is here from new ukraine prashant's here all right everybody's fantastic so um if somebody pops in a little bit late just let them know what the pin code is it should be at the very bottom of the screen but for some reason it disappears um if one or two of you want to jot it down and then if somebody joins late and they need to know it you can just say here's the here's the pin code all right all right all right um oh and thank you carlos uh studying for encore but i hear every weekend for fundamentals love it i'm glad you're here every saturday on the on my discord server it's free we have a ccna uh office hour discussion and then every sunday at 11 a.m pacific we have this quiz or similar quiz and then right after we'll be in the discord server as well just to follow it up okay let's get this party started it's a party by me keith barker so glad that you're here cisco ccna dns and dhcp i believe it's just ten questions here's the first one it is multiple select the show ip interface command can reveal which dhcp related information there's at least two correct answers on the board maybe more what do you think the faster you answer correctly the more points you get [Music] [Music] foreign [Music] so if you feel if you feel a burning desire to answer in the chat i would ask you to suppress that urge that way i want to put you on timeout join the game the pin code is at the bottom you can use a web browser or the app on a smart device hit the pin code and you can actually participate in the game as opposed to just getting silenced in the chats [Music] i'm glad everyone's here including mauricio from costa rica welcome welcome [Music] so [Music] okay let's talk about that for a moment now also what i did a little bit tricky a little bit sneaky is i did this i i put this output with a slow show a slow reveal which has the answer to this question uh but i the fact the key is if you can answer this before it reveals itself that you get more points and so show ip interface here's a trick that i learned a couple decades ago i'm going to share it with you right now and that is anytime we have the word ip and a syntax like show ip interface brief or ip address or et cetera that means ipv4 if it's version six they're gonna tag on some flavor of v6 with that like ip v6 so when you ever see ipl by itself like this that's just for ipv4 so uh the question was what can it reveal well it's not going to be any d8 and no ipv6 information at all and that blocks off red and yellow those two and what this will show with show ip interface brief it shows that the address was received via dhcp so on the interface somebody said ip address dhcp enter and then it did a discover offer request acknowledgement process client client server server and got that address it also see here what else was blue say uh i don't remember what blue says we'll see that in a minute oh here right here this is also showing us right here that we have dhcp relay enabled on that interface so ip helper was used that says the adhd per server is 10.1.0.55 is it likely you're going to see a dhcp client that also has an ip helper address no that's not too likely but i just did this so i put it on one screen but that uh that was the answers for us ipv4 dhcp relay information and dhcp assigned ip address green and blue fantastic let's see who's on the top of the heap here knowing bunny way to go all right and there's nine questions to go they're all about a minute a piece here's question two it's multiple select what may cause a non-authoritative dns result i'm looking for three answers look for the one that's not valid and choose the other three good luck everybody and it bell if you want me to go over dora uh be uh if i don't cover it in this quiz please join me right after on the discord server ask that question of me directly and we'll just chat about it i'll give you an explanation in more detail and go with them uh you just go to kahoot.it open a new browser or use the kahoot app and at the bottom right hand side of the screen is a pin you put in that pin and that's how you can participate live we've got seven more questions after this one i know eight more so there's plenty of time jump in there i'd love to have you [Music] okay what may cause a non-authoritative dns answer let's take a look just peeking for a moment at this output what is this output all about um i'm grab a pen so this is ns lookup which is a fantastic tool that goes out and queries a dns server that you have configured you can also in interactive mode you can specify what dns server you want to use so this ns lookup says please give me the ip address or addresses behind this name because that's what dns does it maps and resolves names to ip addresses so that's my dns server that i'm currently using which is a open dns server umbrella from cisco and this says it's a non-authoritative answer and for that name ogit.online it has two ip addresses associated with that so why is that non-authoritative so let's say we have some root dns servers and we have some dns servers for com and for let's say dot in and for org etc and then under each of those then there's companies let's say you have like i have a friend rohit who uh is involved in a company called acet acit.in and then he's got well he has or he has hired a dns server that's responsible for all the names at asit.in and so that if we got an answer directly from this dns server that would be referred to as an authoritative dns answer it's coming from the start of authority the dns server that's responsible for that specific domain so when a client makes a request so this is us over here meaning not us but like you and i uh us the uh us together we make a request to our dns server our dns server is first our clients can look at the cache first do i already know says the client if we're just doing a regular dns request do i already know what that ip address is behind that name if it doesn't it makes a dns request that dns server if it has in the cache it can answer it if it doesn't it can make a request and it's called a iterative recursive request that's basically going out walking the tree asking the dns infrastructure until finally he gets the name and then it comes back and it's cached all the way back so this dns server would cache it the client would cache it and those would all be examples of non-authoritative because they're all indirectly coming unless we got it directly from the horse's mouth so what may cause a non-authoritative dns result a local server cache it's this example here uh service provider cache which would be an example for maybe the server spreader we're using so me this is an internal dns server maybe we have a dns server that said our service provider that it hasn't cached uh the device local cache so any of those three answers would be a reason for non-authoritative dns results i love it you won't uh and we got a lot of great answers too on that so perfect perfect perfect here we go uh question number three of 10 is it possible to map multiple ip addresses to a single dns name and the faster you answer correctly the more points you get go go [Music] and josec the local cache would be in reference to whatever device you're looking at so if you're looking at a local dns server that would be a local cache on the dns server if you're talking about the actual client it could be a local cache on the on that windows or linux or mac client or mobile device so it's based on the context where that's being where that term is being used but oftentimes local would refer to the pc all right is it possible to map multiple addresses the answer is yes and that's the example i think we had from just a moment ago there's one name and a couple ip addresses behind it and one of the benefits of that is the dns can round robin so it gets a request for one uh name resolution it can hand that one ip address and then it gets another request for a different the same address that name again and it can handle these second or alternate ipods or it can hand out all of them so it's a way to the reality is the question was can we map multiple ip addresses like this example to a single dns name the answer is absolutely yes all right here we go question number 4 of 10 it is double points where is dhcp relay configured in this topology [Music] and cornell's i would prefer the answers in the interface for the game that's where the answer should show up so if you're able to go to kahoot.it in a separate window or on a mobile device use the game pin and answer there thanks for asking [Music] so [Music] [Music] all right where is dhcp relay configured my my thought would be this if this is the client which is documented here it is and this is the dhcp server and this is the router for this segment uh it would be implemented right here on the interface as part of that vlan that part of that broadcast domain so when the client does the discover message saying hey i'm looking for a dhcp server this router who's configured with dhcp relay to point to this dhcp server can go ahead and take that broadcast that the the discover message and unicast it and route it over to the dhcp server who then identifies where that came from it came from 1010 it sees it asks itself do i have a pool of addresses associated with 1010 if it does it then unicasts back to this router the offer coming this way and then the the dhcp relay device then forwards that offer into the network where the client takes it the client says wow great offer i'll take it that's a request and then that request gets routed through the network back to the dhcp server and then the acknowledgement coming back gets routed as a unicast frame a packet back to r1 who then forwards it so the pc doesn't know it really doesn't it doesn't well the pc doesn't know based on the traffic behaviors that the dhcp server isn't local it would know however that the dhcp server's address is like 192.168.1 so it'd be able to tell it wasn't on the local network but from a functionality perspective it doesn't care it did a discover there was an offer there was a request there was an acknowledgment and this guy is happy happy with an ip address so where is it configured it's on the interface that's local to the network the vlan where the client is so if this was a multi-layer switch and this was vlan 10 it'd be interface vlan 10 on the multi-layer switch where we would enable iphelper it has to be on the same layer 3 interface in the same broadcast domain same vlan as the clients who are looking for a dhcp server all right we are making progress here and we had a lot of people on the right answer and i appreciate everyone who's studying and practicing and improving that's the name of the game that's how you win just never give up just keep on studying i'm glad to have you here silly llama you're crushing it seven thousand followed by fabulous finch create kitten glowing sea lion and knowing bunny still in the top five here's question number five it is double points cisco routers use the command ip address blank in interface configuration mode to become a dhcp client i agree dan kittens are great [Music] foreign [Music] [Music] ah so proud of you all right dhcp is the answer i'm looking for here ip address space dhcp press enter and that starts the door process on that interface as a client on the cisco router all right here we go question six of ten it's also double points what is the syntax needed on r1 gigabit interface zero slash two and this is a dhcp related question [Music] [Applause] i agree joshua geckos are pretty amazing too [Music] so oh beautiful beautiful that's exactly where we would configure the ip helper on the same subnet where the clients are and that's the syntax to do it so good way to go ip helper why isn't it called dhcp relay if that's what the feature is that's a long less that's a long story that i don't know the answer to um that's when they developed it the ip helper also ip helper can be used to forward additional protocols besides just the udp used by dhcp but great job alright here we go we are on question 7 of 10 rounding the corner multiple select what can cause an ipv4 address conflict when using dynamic host configuration protocol i'm looking for every answer on the board that is correct [Music] and round 81 thanks for the help for your fellow game players appreciate you [Music] [Music] all right and let's talk about why this one isn't correct slack is involving ipv6 and so this question is about ipv4 address conflicts and so with slack it's ipv6 so it takes another picture and when a dhcp server is going to hand out let's say i have a pool of addresses let's say 10.1.0.51 through 90. so we'd set up the network and the dhcp pool configuration and then we do the excluded addresses to exclude 1 through 50 and also 91 through the rest of the range which should be 255 or 254 for valid addresses that can be used and assuming we have those this fire the cisco devices acting as a dhcp server they will also they will do a ping check by default in attempt to determine is the ip address they're about to hand out let's say it's 58 is that ip address it's about to hand out does somebody already have that and so it'll do a ping first just to verify whether or not somebody has it now unfortunately there could be a local firewall as dan uh reminded me a few months ago and i thought man that's exactly right if there's a local firewall on a device that does have that address already.58 is statically configured and the fire and the dhcp server pings it and this guy doesn't respond because of the firewall running on the software on this computer that could cause this dhcp server to hand out that ip address to the dhcp client in question so manually configuring ip addresses or local firewalls that don't respond to the pings or no ping check done by a server all of those could be reasons for a dhcp conflict and also another this was discussed in the office hour yesterday we could also have a proxy arp now traditionally how an arp works is you have a device that says i wonder i wonder what the layer two address is of the ip address 10.1.0.1 for example the default gateway so it will do an arp request and then there's an arp response hopefully and the client learns the layer 2 information but what if you have a device that's just out of the blue generates an arp message that says hey here's my layer three dress here's my layer two address or it does it on behalf of that's a that's a gratuitous arp excuse me gratuitous harp is what i wanted to start explaining a gratuitous arp is when we didn't actually ask for it but somebody did in our advertisement with their layer 3 layer 2 and if that also is seen by the dhcp server it'll say whoa the ip address i'm about to hand out i saw gratuitous art for somebody already has that address and it will also exclude that from the pool as far as being able to hand it out so it could ping and exclude ip addresses or i could learn via gratuitous arp and not hand those out and proxy arp is yet a different discussion for another day all right great great great let me take a look at the queue all right yeah yeah thank you uh yeah blendinator is like helping me out keith it's not do you mean gratuitous not proxy thank you for having my back i appreciate you all right here we go question number eight three to go including this one double points clients are not able to do name resolution i'm talking about dhcp clients they're not able to do the name resolution why is that i'm looking for a single best answer joshua wow four i have four kids so my study times were relatively short yeah i hear you and when i got my first cca in 2001 i had several young children i know it's tougher when you have a full-time job you have kids and and the family so i'm proud of everybody's putting in the time [Music] [Music] oh right let's take a look at this output together and just confirm so this is a dhcp pool not a nap pool so we have lots of different pools that we can use on a cisco router and this is a pool used for dhcp uh the range is uh what's the this is the network the 64 subnet with this mask and then we have a default router and if you've joined me in subnet saturdays or if you already know subnetting you might be able to identify that the 64 subnet uh that this dot one is not the same subnet so basically we're misconfigured here we're handing out imagine like this so this is our client that's asking for a dhcp address and the dhcp server will say it's right here and it hands out all this information the client gets it and this is the network and then we have a router and then another router router 1 router 2 router 3 just for emphasis and let's say that this ip address is 172.16.12.1 right there so if this client is trying to get off of this local subnet which is the 64 subnet it doesn't have a local default gateway it's hard to get off the local network if your default gateway is not local to you so this is a misconfiguration right here the dns server can be anywhere that's reachable via ips that's not a problem and the lease is that's number of days hours and minutes for the lease so the reason here that clients are not able to name resolution is that the gateway handed out by this misconfigured dhcp server the default gateway the default router isn't local to that same subnet all right great job and i think we have two more question nine of ten what is the purpose of dyn's domain name system what is the purpose of dns [Music] [Music] wow look at that that that's like one of the best overall scores i've seen in the two years we've been doing these quizzes every sunday at 11 a.m pacific so good all right we've got one more question and here's the top of the heap at this point silly llama great kitten smooth gator shining urchin and great b but the final question could tip the scales who's gonna do it here we go question 10 of 10 it's multiple select which of the following are true regarding dhcp there's at least two answers that are correct and maybe more take a moment and give it your final shot [Music] [Music] [Music] [Music] all right all right who did i we had 26 people on red so the other answers all look pretty good let's just take a moment oh i clicked on next let's look at the podium and then we'll go back to that previous question if it lets me hit the wrong button [Applause] [Music] silly llama congratulations everybody [Music] [Applause] [Music] and i don't think it's gonna let me go back to that question but if you want to join me in the discord server right after i'll be happy to elaborate on any of those questions if you have questions about those questions and here are the toughest questions from the group of ten and that's these three questions and we had 21 percent 24 27 and all the other questions we had better accuracy as a group all right if we could just take the exam as a group we'd do great yesterday oh my gosh it was kind of fun in the office hour uh we went through some practice somebody said can you review these and so we looked at somebody else's practice content that was publicly available and uh went through and i i missed a couple we were going through a pretty good clip and i said you know but i think i got like 80 percent i still have a double cci you can get 80 and feel okay about it uh you can too because they don't require perfection in the ccna it is require a passing mark all right and the more practice you do and the more labbing you do the better you'll get and i also would love to get some feedback from you as well so go ahead and if you would take a moment provide feedback via the interface and in just a moment right after i close the stream which is going to be in about 30 seconds join me on the discord server there's a link for that in the video description and it just will be in the ccna voice room it's just an open forum and if you want to go over any questions i'll leave the kahoot game up so we can do that as well so please if you're studying ccna or just want to reconnect with the foundations and the and the basics please join me my name is keith barker i'm a double ccie i love cisco technologies and a lot of others but cisco in this form and i have the quiz every sunday so if you want to mark your calendar adjust it for your time zone every sunday 11 a.m pacific time join me i'll be right here and then every saturday at 10 a.m pacific time we have the office hour which is an open forum over on the discord server where we'll answer your questions regarding the ccna technologies provide examples and so forth all right so i'm going to send you out with some music and my appreciation for being here it's absolutely great to have you and if you're going to join me in discord i'll see you there in a moment if this is the end of your journey today with me fantastic having you i look forward to seeing you in the next event thanks everybody [Music] [Music] [Music] my

Channel: Keith Barker

Views: 5,119

Rating: 4.9733334 out of 5

Keywords: ccna, cisco, 200-301, Cisco CCNA, Cisco Certification, ogit, Keith Barker

Id: xLqKjw_9-dg

Length: 34min 7sec (2047 seconds)

Published: Sun Jul 25 2021