BGP: Communities!

hey everyone its Jon and today we're going to continue on the bgp of video series so today's video what a why disgust as bgp communities know what our communities communities are effectively tags what you can use to influence written policy no there are four well-known communities which I'm going to discuss on a later video but today I just wanna discuss communities more generally so I thought the best way to approach this was to simply concoct this little scenario and you can see how communities play out and see how we actually can control the decisions just using the community tags so down in the bottom here we've got es 14 watches IPV 0 solutions that's could be a company of any cane we own this company this is a company and we're going to be advertising your network to your ISP so it can be found a globally which is gonna be a 140 141 $40 0/24 and as you can see we have two ISPs which are connected to on the left-hand side okay a s 23 that's a SP 1 and it's going to act as a primary internet connection this is your high-speed internet connection on the right-hand side however I've got this is Peter and it's just really a backup there's the speed on this an internet connection is very slow as a cheap connection it's really just used as I cannot feel over we don't want to be inviting traffic through this link you want all the traffic to come through the high-speed air connection now up to the top here we've got ES 89 that's just getting that general transit es au temps on it and on the right hand side we've got this random company with just anything basically but they are also connected to is Peter but not is P 1 okay so what we've got here is a high-speed connection and a low speed connection so if you remember from the previous videos with that some traffic engineer and if we want to invade traffic over this link rather than this link we could use es path prepending because these are two different ISPs and that can help influence and bond traffic traffic coming towards us no let's see this is common that the ISP is actually filtering es path prepending because they don't want you spam I know 50 or over many paths people's just saw the the es path becomes artificially long they may see loss and we felt like we don't want you to do that so what options do you have you don't want the traffic to come through here and especially if you think about it let's see someone from a random company wants to access your website whatever your hosting here ok they're connected to ISP - so they send the traffic out here know the BGP decision is not going to be on like a general IGP metric of like bad a bandwidth the way OSPF would be what it's going to do it's going to see the es path and just say okay well the es path the quickest way is through here doesn't just going from one ear so that's es rather than go the more circuitous route of over here here here here here and here but actually this path despite looking longer and go through more rows more not can be all high-speed links and no special that's like is high-speed of course rather than getting through maybe some cheap or I don't know maybe such a t1 connection not very fast whatever it might be okay but it's not desirable to be inviting all your traffic or with us link we don't have es path prepend interest because that's ISPs just felt on and it's not acting on it anyway so what options do we have ok what we would do here is you would physically call up the ISP and I mean actually pick up the phone and communicate with them you talk to them and you would say and something on the lines of can you give me your community felt last effect earlier community policy lust and they will send you like an Excel spreadsheet and it would to have all these communities all these numerical values and correspondent written policies no mocked up a very small version that's obviously a lot longer but it would look something like this so they've it's Angeles and effectively because well I'm getting ahead of myself what you may see them before as Lawson we can do es path prepend and you are blocking it so how about you change your local preference to 130 or 240 whatever it may be for me and the ISP says no I'm not going to do that because that's just it's it's too hard to control written policy I mean try and map all that if every single customer wants to do that then they would need to have an individual policy and individual BGP policy for every single a customer unless he get very very messy very hard to troubleshoot and just not very good practice so the way turned out like I said he would phone them up and they would give you a list of communities now you can actually get that desired effect by years in the communities so all you would do would be is you would look at the community list and look at the policy no we want the policy to be less desirable to go through a vest link here so really if we set the local prayer phones to 50 rather than the default of 100 this would make this link undesirable and therefore if it's been advertised through our ISP that's is pica get over this link here that's pathway or rather okay so I can say we want to influence the local preference but just for know up and asking them less than arbitrarily can you just change this for us they're gonna say no what they want is to use as nice template and we can signal to them by using community values to see what part of the template we want them to apply to us okay now this may sound a little bit abstract and obscure but again once you see and practice you should see what I mean so let's just go with that's just me okay so what I'm going to do as first we're going to advertise our network okay so that's as I was just now and we're gonna let the world know about a 140 140 140 slash 24 so we'll do Network 140 140 140 is you know and the mask is a slash 24 so let's put 90 bgp okay so of no advertise that mt bgp and if we go to here let's see if Isis got up okay so the next hop as you can see is going to be 14 4501 so it's going to go on through this path effectively clearly but remember we wanted this cottage written on us so what we're gonna do is we're going to look at that community las decenas that's Excel spreadsheet and say okay we want them to set the local preference to 50 for us on that link so what we need to do is send out prefix but send that with the value tag of the community tag 45:10 okay now what well see is when you're doing this bgp communities have got em and all the format and a newer format the newer format is much more readable and if you tape an IP bgp forma you're gonna see that if you do sure we do rate it and the way of an es number followed by the policy it's going to convert into a much longer number and it'll be party rate so IP bgp format will let you see it and the simple format so that's a little tough for you do that okay so what are we going to do we're going to go in here and we're going to clear a prefix lust so the IP prefix lust and just call it lust and we're going to permit the network okay so we're going to do a 140 140 140 this is the the prefix which we are targeting to attach em the the community value and with a trip map and we'll call it mmm what we call it just call it John I'm at 10 and we're going to match the IP address and the prefix last called last which is the 140 140 140 zero and we're going to set the community and here as no like I say that's what the old format see these cannot long numbers here and that's the move okay so we're going to have the autonomous system number and the number that's gonna be the format will be used so legacy witness that are close that me graphic yeah okay so 45 10 knots we're gonna see activist will we want the local prisons to be 50 so we'll set this prefix to be 45 10 okay so 45 10 just a rip map John I'm at 10 eggs oh okay so I'm gonna do it at the Ritter bgp a 14 and we're going to stand back to your neighbor here which is 14:45 0-2 okay so neighbor 14 for if v is 0 to r it's written map John it's okay now what we also need to do as communities are not saying by default okay so what we need to do is also tell this st. the community value so we're gonna advertise that prefix okay with that new community value no like I say we phone up them as they asked me one that's positive they're going to apply this policy on their n boned interface so they're gonna have a bunch of em communities so what I'm gonna do here is this I'll just make this up we need to use a community let's order an IP community lust and we'll just call this one or make a standard one and we'll call this one p1 for policy one okay just keep it simple and what we're going to do is we are going to permit and actually permit the community value so in this case it's gonna be 45 10k so 45 10 is number one and we'll have policy to call that Peter and just make the next minute 45 was 45 20 and p3 would be 45 there so these are all these values okay right so now I'm going to do is create a rip map and we'll just call this one policy this is gonna be the policy template and what we did will do permit 10 and what I need to do is do match community and when it can match the community name here's okay so we'll march on P 1 which is going to match the tag 45 10 so we'll match community P 1 okay and we're going to set the local prayer funds to be 50 this is our template okay and we'll do rip to map policy permit 20 and we will match the community Peter no Peter is 45 20 and that will have their set the local preference till 120 ripped map policy permit theater much community now this would be a very very very long less than a template they'd have less exact less from every customer this is not just unique to me I'm just writing it here for you see what that's been already be devised by then before this end that's lost Otis so 45 30 so that would be we're gonna do a bit of yes path dependent on this one and we'll do set es path prepend last es and it was to a thing or prepending twice okay and brush leave Ella or if they're a rich map policy permit 40 it's not the filter them okey doke so I've got this rip map case book all these policies so if somebody marks the at they said the prefix which the violet eyes be advertised it with the community value of 45 ten forty five ten or much but p1q minute last and because of that local prefer to be set to 50 if we marked the rip worth m/45 30 instead it would be path P painted on their end by two values okay so what I'm gonna do now is I'm going to just attach that rip map to the neighbor so the road BGP and what n is Peters will 45 I'm not going to match to the neighbor here which is for if a 1445 is 0 114 4501 and writ map policy and okay and then we'll do a clear IP bgp soft okay now look at that suddenly the local preference for this route is faff there you see that show IP BGP so we as a company so let's just review this okay we as a company have advertised less prefect of advertised LT this is P and this is P we have thus contacted this is P here and said send does your list of policies okay so we know what to tag we have looked at the last of policies because we want the local player has to be 50 and just phoned them up and ask them to arbitrarily change it they will not do they'll have that standard policy lost if you say and that's where tag it will automatically filter on that or match on that and you'll get a desired effect we have said we wanted 50 so if master prefix with the community value 45 10 okay so I've sent that prefix a little less and a face with 45 10 and we've got the policy and bound on here to match that so if we look at us and be the issue IP BGP sure IEP BGP 1 for what we're gonna see as it's got there it's there okay the community value is 45 10 and because of a rip map 45:10 matched p1 remember and are 45 10 matched p1 p1 there and as you can see on the rip map p1 NICs the local prayer funds set to 50 ok so even if this is P was filtering es path prepending we can still influence written policy from within named by standard name tags which match their policies so we can see I wasn't treat the traffic this way according to how you you mark it okay so let's have a look at the desired effect so I've now got what I'm gonna do is I'll just advertise um I'll create a lot more titles in the BGP just to keep us simple comedy and we'll just make my face look back it roasts it all the it's okay and the writer of BGP five six seven near button will just put on the BGP okay well what did I do that what a denier but I can that was selling BGP if I was like yourself in it what can I should have been okay so advertise the eight networking I should see we've got it here yep okay so now we've got this a random company and they are going to try to reach your website and like I say we don't they happen to use the same ISP is we do number two but they don't use number one okay so with normal es path the shortest path would be through this link but we just want this cheap link or backup link we don't want to be invading traffic over it unless we really really have to so what we've done is here we have the story says link by setting the local preference to fifty so the default one hundred will be favored so when this customer sends it to their ISP the ISP is not going to send it that's where it's going to send it the long way so I just check that okay sliced your trace will do it trace Quito travel do i standard one mother and will trace it to one four to one and there's also dresses all there is oh you know what many clear bgp forced me are you not with em I'll just change that every second what an office to be on just purchase an office first okay social IP BGP one for right okay so that's why should a bit senior okay some I've got the right here and as you can see this is the one for Everett okay so the one for Europe the initial path as 15 it's been changed if left in oh and the other path is at the default of 100 now you can see the other path as the best path okay that's that one there and it's going through 45 45 45 - which is 45 45 45 - rather than the 1445 you see that should go back to that the 1445 has got a local preference of 15 oh and the other one it's cause default of 1 and it's going that way so let's check that again do that again that's all working and the protocol is IEP of course and it's also dress it okay so no that's personal is gone they're never implemented that policy company random company is going to try to get to go off and weather as well or sell them and water see the way it goes and you can see the path that's taken okay so even though it's directly connected to the same ISP as ours that's ISP is taken over the longer path okay so they're connecting to here that's going through here let's go over 45 45 45 it's gone 45 18:02 let's go on over the 18 path here you can see it here 23 your name which is there obviously and it's going over 23 22 23 23 23 and then it's gone over 14 23:01 watches our high-speed internet connection you see that so we are still utilizing a very fast expensive high-speed connection rather than the cheap back up slow connection here even though that's what alternately go this way but by the use of communities we have signaled to the ISP to influence the ISPs policy over the prefect we're advertising and because of that we can actually influence the direction of our random company gets to our network via epsilon ISP okay so that is the end of this video on communities the next one is going to be on well-known communities which is a weber Defensor sim is the same it's the same cat hope it's the same thing there's just a couple more just four more and thankfully implement and that'll be discussed quite heavily in the next video okie doke so I'm gonna wrap up here and try keep it as short as possible and that's the end of it so thanks very much I'll see you guys soon bye bye

Channel: IPvZero

Views: 3,484

Keywords: CCNA, CCNP, CCIE, BGP, Community, Communities, BGP Communities, Border Gateway Protocol, IPvZero, Network, Networking, Free lessons, Free networking, routing, switching, service provider, cisco, lab everyday, #labeveryday

Id: kAOGPjiH3dw

Length: 21min 22sec (1282 seconds)

Published: Sun Aug 18 2019