BGP Troubleshooting Ticket 3

[Music] hi guys this is amar and welcome to armor tech stuff so guys in this video we are going to focus on yet another bgp troubleshooting ticket and the problem statement in this particular ticket is that not able to paying destination 10.1.1.1 from source60.1.1.1 so this is the problem statement and we need to solve this issue so where is source60.1.1.1 so guys here is the source 60.1.1.1 so this is basically one that is move back one of router r6 is the source and the destination is here on router r1 so r1's loopback 1 is 10.1.1.1 that is router r1's loopback so that is the destination so from here we will just mark or show you that is from here we are from this loopback we are not able to ping this look back so this is the problem statement and we need to solve this issue uh so this is the overall picture of the my virtual lab so we'll try to solve this issue um so we'll go step by step in solving this issue so for that we'll go on router 6 first of all and here is router 6. so from here i'll just verify once the loopback interface show ipm3 so this is my loopback one which have the ip address of 60.1.1.1 which is correct the loopback is up that's good uh let me check on r1 itself because so r1 is in yellow color so is the prompt of r1 so let me check here also show ip and brief schweipin brief and you can see here loopback zero it is uh you can see it is 1.1.1.1 so we need to pack one so this is correct 10.1.1.1 so low pack one is correct it is up that is good so let me check from source to destination i'm able to ping or not so this is my destination and sources 60.1.1.1 and i'm not able to pick here guys uh instead of 16.1.1.1 i can even write interface loopback one that will work but here you can see the ping is not happening so this is the problem and we need to solve this problem uh whenever you are working in a real environment you will get such kind of issues where a source will be given a destination will be given sometime a port number will be given and you need to troubleshoot why the communication is not happening so let's troubleshoot this further so let's check on r1 whether we have a route to reach the destination or not so you can see we do not have the route xf2 is the destination let me check the routing table you can check the routing table all are connected and the loopback interfaces in the routing table there's nothing else in this routing table uh so basically in this architecture in this diagram you can see that r6 router just have only one exit interface okay that is uh this so we need to check whether this ebgp which r6 router is forming with r4 is up or not and the ip address is 46.1.1 dot 46.1.1.0 24. so i've taken it like 46 so it is between router 4 and router 6. so this is how i've taken the ip address so 46.1.1.04 so let's check whether this link is up or not and the ebgp between this two routers is upon one so let's check it so i'm on router r6 show ipvgb summary okay so you can see that the neighborship is in the idle state okay the neighborship is in the idle state of means it is basically down so we need to check why it is down so we will try to troubleshoot in that sense that why this is down so you can just check over here first of all the interface uh which is uh ethernet let me check what is the interface ethernet 2 3 the van interface yeah and you can see here it is administratively down so we need to make it up so for some reason i made it i missed it down and it remained administrative down i think so that is example 5bipgp with r4 is not coming on router r6 so let me make it up so i'll make it up that interface i'll make it first of all because because of that i'll show you one thing you know before making it up summary okay so even if you check now whenever you find any bgp neighbors down you try to bring that which we need if you're not able to ping that bgb neighbor so that this ping should happen then only the bgp neighborship is going to come up because bgp works on tcp port number 179 and for the tcp session to come up the layer 3 connectivity should be up between those ips so here we do not have that layer 3 connectivity itself the ping is not working ok because ping is again going to give us the layer 3 status of that particular ip so it is it is not up so let us make it up the interface which i was slash three i'll simply do no shirt and now i'll try to ping it it is up and i'm able to paint so i'm able to ping uh 46.1.1.4 so this particular interface guys this particular interface was down so we made it up okay so once we made it up we we are now able to ping uh 46.1.1.4 from router 6. so we're able to ping now let's check whether our bgb neighborship came up or not so just go on r6 and check it over here itself still it is not up still it is the idle state it does not come up uh let me check on r4 as well surely it will not be up on r4 also should i pgp summary you can see uh with r6 it is not up it is in the idle state so we need to troubleshoot again more something something is missing which uh is not because of which the neighborhood is not coming up so we need to troubleshoot that uh guys you can see certain certain logs are coming once we made that interface up and the ping was started happening you know some some logs are coming and you can see some locks are coming and these are the notification messages for bgp and uh this indicates uh this this notification message basically says that it's tcp 6 bad authentication that is bad euth that is the bad authentication so something is related to bad authentication with this neighbor which is r4 for which we are troubleshooting so for something six no md5 digest from uh 46.1.1.4 which is r4 to r6 which is 46.1.1.6 so in this way you need to read these messages so we are perceiving this messages something is wrong with the authentication i think so so let's check so to check it i'll just give this command show run so let's wait and also on r4 also we'll give the same command showrun section pgp so this is the neighbor ip right so what i'll do is i just focus on this particular configuration [Music] 46.1.1.4 and let us focus here also so this is the configuration just paste this configuration from r6 on a notepad [Music] also the configuration from r4 guys i'll paste over here so this is the ip address just check and just paste it so whenever in real environment also whenever you are troubleshooting or want to make certain changes in the live environment this guy is always the best practice to actually note down on a notepad or that what all changes you need to make and then only paste it so this is for our first so you can guys clearly see the difference that password is not configured for on r4 so for r4 we should have in configuration where we need to tell the r4 that for this particular neighbor that is for r6 that is 44 46.1.1.6 you should have a password this so that password you should that configuration you should have uh so let's do it so what we are going to do on r4 is will be entering into router bgp 300 because it's a member of our as300 and then we are going to give this command neighbor 46.6 and this password okay so basically password is the command and this is the encrypted password so uh this is an encrypted password with type 7 password so you can decrypt it how to decrypt it i'll paste the link in the i button or in the description section this video please check it uh how to decrypt a password type 7 password but here you can again you know paste it with encrypted format itself uh with this uh keyword seven password space seven you can do so it will work i'll show you how it is so this is the configuration which i need to make on r4 let me make it quickly i'll just copy this i'll go on r4 and i'll show you one more thing okay just on the debug on r4 debug ap now i'll just go see you can see certain messages but i haven't pasted it now i will see some messages okay a lot of messages these are the uh this is the bgp neighborship is coming up so a lot of messages are exchanging you can see a lot of messages so yeah just try to explain you you can see here that it has gone from active to open send so the open messages are going to be sent and in open messages certain parameters have been exchanged the version number the hold on timer and everything bob tried to stop it [Music] so you can see here open send to open confirm the status change from open confirm to established so this is how the state is going to change earlier it was inactive so it came from active to open sent and from open sent it came to open conform and then open open confirm to establish establishes the final state or the the actual state for which we means the bgp is up once we have this established so you can now check here show ip gp summary okay so now the bgp is up with r6 now let's check on r6 as well you can on r6 also you can see that uh once this neighbor came up since r4 came up this messages which were related to the password or the authentication have stopped so let us check here also show ippgb summary so you can see it is up now so in this way we have made this neighborship up but still we are about to get our 1.1.1 you can see here we are not received any doubt related to 10.1.1.1 so still would not have it in our routing table so let's double shoot it more so let us check why we are not receiving it should i be vgp neighbor uh 46.1.1.4 i'll just paste it over here let me check whatever routes we are receiving from okay inbound soft reconfiguration not enabled for this one okay i'll change it no issues i'll go into router bgp 600 and for neighbor 46.1.104 soft reconfiguration input and now i'll check what all routes i am receiving from router 4. so this all the routes which i am receiving a lot of routes you can see i'm receiving some routes of r1 as well that is uh 10.1.1.2 network i am receiving 10.1.3 i receive but i am not receiving 10.1.1.0s network i am not receiving so i need to check it why i'm not receiving you can see here r once this network this loopback 2 is i'm able to receive it from r4 okay and these are the paths which it is going to take so why i'm not receiving it let me check let me check on r4 uh just go on r4 and i'll just check why it is not not advertising let me check here should i bgp uh 46.1.1.6 which is r6 advertised routes so let me check which all routes it is advertising you can see it is not advertising 10.1.1.0 or it's not advertising but rest of the routes it is advertising okay so let me check so for r4 you can check whether we have a route on r4 or not will not have a route also here also we are not having a route so r4 is going to now let's check on r4 whether it is receiving the routes from its neighbor or not so should i be bgp neighbor so it have two neighbors okay one is this r2 and r3 so either it will get from r2 what we'll get from r3 so let's check from r2 whether it is getting it or not so r2 is 24.1.1.1 uh received routes so here also you can see we're not getting the route uh i'm also not getting the route i checked it uh with the neighbor r3 as well 3.3.3.3 you see routes you're not getting the route as well here also you can see we're getting a 10.1.2 0 but you're not getting 10.1.1 so basically what we checked is i'll just explain you again that what exactly we checked so what we checked was uh on r4 we checked that uh for this particular 10.1.1 dot 10.1.1.0 we're not getting this route from this neighbor and it is r2 and also from r3 okay so we're not getting from both the neighbors so let's go on r2 and check whether r2 is getting the [Music] this particular route that is from r1 to r2 okay whether we're getting it from here or here so we'll just check it from from r2 as well now so let's just login into r2 now it's time to log in into rd so it's my favorite router it's green color so it's my favorite so just check now show ip pgp neighbor uh 1.1.1.1 is the name received routes okay so just check it over here we have receiving some routes but again guys we are not receiving 10.1.1.0 central so there's some issue with r1 now let's go on r1 and check so on r1 you can see what i have done is i just check whether i'm advertising it or not vgb neighbors to advertise routes so here you can see that i'm not advertising 10.1.1.10.1.1.0.24 but i'm advertising all these routes so because of which on rcs also you were able to see this routes okay so let me advertise it i'll just go into configuration mode router bgp 100 and give this command to advertise the routes from vgp you need to give this command to network 10.1.1.0 with this keyword and marks and the submit marks is slash24 now now i'll check it whether it is advertising to r2 now not yes now it is advertising to r2 so now r1 is advertising the route 10.1.1 but zeros that's 24 to r2 let me check on r2 now whether i'm receiving it or not yes on r2 i am receiving it let me check on r4 now comma subject from i2 r2 i'm receiving it from r3 also i'm receiving it so i'm receiving it on r4 let me check one r6 the ultimate router the source router yes i'm able to receive it now i'll ping it uh ping 10.1.1.1 source is 60.1.1.1 that's it now we are able to pay it if you want to see show ipad out should i peer out 10.1.1.1 you can see you're learning this route from r4 that is 46.1.1 and you are learning it via bgp okay and the ed value is 20 so you can see this details so guys in this way we can troubleshoot some of the complex uh tickets which you will receive uh when you're working in a real environment so i will always recommend uh all my subscribers or former tech stuff that do practice a lot on on jns3 or even g or package packet pressure because you know once you practice you will have a good hands-on which will help you eventually when you're working with a real environment so guys i'll stop here in this video this video is a bit lengthy video uh but i think i'll come up with more uh complex sort of issues in the same lab but with more complex issues slowly slowly in the troubleshooting tickets so guys i'll stop here um before ending this video i'll request you to please subscribe my channel number tech stuff uh if you really like my videos please do like and also comments on my videos which will motivate me to make more videos thanks for watching have a nice day thank you

Channel: Network Engineer Stuff

Views: 3,404

Keywords: BGP Troubleshooting ticket, BGP troubleshooting scenario, BGP Troubleshooting commands, BGP troubleshooting steps, BGP troubleshooting interview questions, BGP troubleshooting

Id: Hwt38xt3Lq0

Length: 22min 23sec (1343 seconds)

Published: Sat Oct 31 2020