BGP Troubleshooting Ticket 2

[Music] hi guys this is amar so guys in this video we are going to focus on and bgp troubleshooting ticket and in this uh bgb troubleshooting ticket what we are going to focus is this particular problem statement that is the ibgp neighborship between router r3 and router r4 is not coming up so this is the problem statement so you can see over here that uh we have this two routers that is r3 and r4 which belongs to as300 and the ibgp that is the internal bgp between them is not coming up uh they are the ibgp neighbors because they belong to the same autonomous system that is autonomous system 300 so that is why they are the internal bgp neighbors to each other but the neighborship is not coming up and that is the problem statement so we need to troubleshoot this ticket so what i've done is i've already taken the console of both the routers r3 as well as r4 so we'll first check on on r3 and then we'll check on r4 so the basic command check the bgp neighbors status is show ippgb summary so here you can see that router r3 have two neighbors so this is router r3 so it have two neighbors one is 4.4.4.4 which is our force loopback interface so the point to be noted here is that it is our force loopback interface so we are forming the ibgp neighborship with r4 loopback interface so this is the loopback interface and which is uh you know the state the state is active means it is actually down it's not up active means it is down and uh it is not up you can see in there and you can also see the as number is 300 which is correct but it is down you can see the other neighbor that is 13.1.1.1 which is this particular disruptor harmonic that is up since 11 minute and four seconds but this particular neighborship is down this one and we need to troubleshoot it so now let's check on r4 what is the status over here show ippgp summary and you can check over here that the neighborship with r3 that is 3.3.3.3 again the point to be noted here is that we are also using r3's loopback interface to form the ibgp neighbor ship so this loopback interface uh run into as300 which is r3 again and it is down it is idle idle this town so you can see it is down since 8 minutes and 14 seconds so it is basically it is down now you can see here the other two relationship or other two neighborship uh one is with r2 that is up the other one with the r6 is down but our focus is not to troubleshoot this issue but our focus is to troubleshoot ibgp in this particular video so we'll focus on that so are there two troubleshooting steps i will say uh primarily whenever you face such kind of issues the very first thing is that you can check the configuration overall configuration how it is whether you have done everything properly or not and the other thing which you can check is the layer 3 connectivity between this between this ips between this loopback interfaces because we are using the loopback interfaces so we need to check the uh reachability between these loop bank interfaces let's first check the configuration stuff of this uh vgb configuration step of both these routers i'll keep it side by side over here and i will check it show run section pgp so by this command you can check the bgb configuration related to this particular router now we can check the buffer here let's check it on r4 as well sure and so this is on r4 you can check uh this both these routers are in as 300 that is good uh we'll focus on this configuration and here on this configuration so you can see our neighbor forward folder for the ipi ipad is absolutely correct remote is 300 that is correct for here also you can see neighbor 3.3 remote is 300 absolutely correct uh description doesn't matter uh but it is correct again here the neighbor forward folder for update source loopback 0 is mentioned over here and here also the update source is mentioned as loopback 0. i'll just check what are the ip addresses of root bytes 0 loopback 0 is 3.3.3.3 that is fine and show ip into pre okay here also 4.4.4.4 that is fine so uh basically the meaning of this particular command and the importance is that uh we are saying to this neighbor that this particular order that that the neighbor 4.4.4.4 for this neighbor the bgb packets should be sourced from low back zero because by default bgb packets are sourced from the outgoing interface and here if you check on r3 the outgoing interface is e2 slash 1 because it's going towards r4 so it is e2 slash once it should not be 2 1 it should be looped back 0 which is 3.3.3.3 32. so it should be that so that is what is mentioned over here which is correct configuration uh and why it is not able to reach let me ping from r4 the layers reachability okay not able to paint and here also i'll check i am able to paint um out of four from here but i'm not able to pick this router it's very strange uh able to bring 4.4.4 but not able to ping 3.3.3 so why it is not able to ping should i be route i will have a route for 4.4.4.4 yes i have a route for folder photoshooter 4 which is pointing towards uh the next stop is 35.1.1.5 which is a router 5 because the packet will go from here and then the ping will go from here to r5 to r4 that is correct but [Music] that is correct but let me check the route we are not able to ping from here so let me check why i am not able to paint should i be route 3.3.3.3 oh it is not we are not having a route for 3.303 guys basically i'm using eigrp as100 i'm basically using eigrp has igp uh for this auto number system this is an internal network so i'm using eigrp uh let me check the configuration of eigrp and both the routers let me check on r3 first show run section eigrp okay so router eigrp 10 i have taken as a s10 that is fine i have advertised this network these are the four loopback interfaces we can see over here and the last one is 35.1.1.0 which is this link that is fine but i have not advertised the loopback that is the reason why i'm not getting around to here you can see over here that show ip cloud eigrp you can see i'm getting each and every network of r3 i'm getting 30s network every network but i'm not getting the three net okay so that is the issue whereas you can see over here the configuration i might have advertised 4.4.4 that is the reason why we are able to ping from r3 section eigrp yes okay so what i'll do is now i just ping 3.3.3.3 [Music] maybe 200 and i'll configure over here see you guys i'm not able to ping over here right router eigrp then network 3.3.3.3 uh the wildcard mask will be you know slash 32.0.0.0.0 and press enter and you'll see able to see here that we are able to pick it the the bgp neighborhood also up here let me check for sure summary yes the bgb membership is up and here also it is going to be here already is up so guys uh we should have the layer 3 connectivity between this two uh interfaces basically uh the reachability of layer three is very important because uh bgp of a bgpgt cpu session because bgb works on our tcp port number 179 so the layers reachability between this uh two ips which we're using uh have to be there you have to have the reachability and then and then only you will be able to form the bgp membership so guys in this video i want to show you only this much uh i'll bring up more videos on troubleshooting um maybe with the same scenario but with the different uh uh different problems from different problem statements and we will try to touch bgp our troubleshooting skills in a different way so i'll stop you guys i'll request you to please subscribe my channel please give appropriate comments and like or please do like the videos also uh so guys i'll stop here thanks for [Music] watching

Channel: Network Engineer Stuff

Views: 3,702

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

Id: OpL7fWfKo7Q

Length: 11min 56sec (716 seconds)

Published: Sun Oct 25 2020