MPLS L3 VPNs in a Nutshell

hi everybody this is mpls in a nutshell really what it is it's layer 3 VPN solutions that leverage MPLS in a nutshell in the past we've had customers like this customer right here customer a once could a different color this she's blue for him we have customer a customer and he's got several sites and so here's a site a 2 over on the far left hand side and in the past what we do we create virtual circuits for them using frame relay we could do a similar functionality with atm and basically do overlays so we can actually have for example a frame where they circuit from the headquarters to the remote site like that well what happens if they have another site well we would add another frame where they circuit and another frame were they circuit another frame relay circuit and this overlay really doesn't scale very well so a better solution that they came up with is MPLS layer 3 VPN here's how they work you've got custom array and customer hang has let's say the 10 network 10.0.0.0 I know it's very creative that's the network they own and they're playing with and they want to share that route with the Farsight instead of doing an overlay what we do is we peer with the provider edge so a 1 right here does peering with PE 3 now that peering can be OSPF it can be e edge erp it could be rip heaven forbid it can also be bgp so we basically peer between a 1 and PE 3 and we give him all of our routes now the game that p3 is gonna play is p3 is going to sign this interface to a vrf it's a virtual routing and forwarding table think of it as a VMware image of a routing table separate from the hosts so they have the global routing table of p3 and you have the vrf routing table that's just for the customary the blue customer those routes inside the vrf get put in a school bus I'll draw one right here so here's our School Bus actually it's not gonna look like a school bus maybe it's gonna be a minivan I don't know so you have this school bus and the routes are taken out of the vrf and put onto the school bus for transport across the rest of the provider network once that provider network on p2 the school bus is over here on p2 p2 is going to take the routes off of the school bus and then it's going to exchange them with a two so a 2 for example then maybe they're running rip over here so we're running a rip between the provider and a 2 what happens is PE 2 will take the traffic or they routes off of the school bus and put them into the vrf for a 2 so this interface also has a virtual routing and forwarding table so the game goes like this the route of 10 is actually advertised up to PE 3 PE 3 puts that exports it out of the vrf and puts it onto the school bus that school bus is multiple protocol BGP so we actually have VPN v4 routes inside the school bus PE 2 is gonna take those routes based on route targets and import them into the vrf that he's using for customer a2 and once he takes them an imports from the vrf they're then shared through that routing protocol so CA with that vrf with a 2 now a 2 if you look at the routing table would have a rip learned route for the 10 network the actual routing protocols aren't too important I mean as far as here we can mix and match but that's the concept of MPLS now the beauty is as we bring on more and more sites for customer a we could put customer a3 right here hang them off of PE 1 and we could still simply pull off the routes and share the routes in this virtual private network for customer a it's called private because it's kept isolated or private from customer be your customer see everybody else there's no encryption involved the private part is simply the separation so the whole game with MPLS VPN layer 3 solutions is having your customers neighbor up via their favorite routing protocol with the cut the provider edge the provider edge taking the routes out of the vrf exporting them into the school bus which is multi-protocol BGP sharing those multiple protocol BGP routes with other routers for example P 3 and P 2 are internal BGP neighbor and they're using VPN v4 capabilities and that's how they share their routes back and forth and then p2 would take those routes export them a story take them off of the school bus import them into the vrf right here at p2 side for the Viera for that customer and share them on their way that's the whole story really there's nothing more to it actually there's a whole world more to MPLS layer 3 VPN solutions and there's lots of great training out there on it MPLS as we get bet back to the top endpoint MPLS is used only right here I'll do it in green right here in the service provider network and the benefit of the MPLS is so that we can label switch the top the top label for the traffic let me I got a few moments may explain how that works one of these routes let me use a different color I only use red I use pink okay when customer a 1 advertise the 10 network it actually is sent to p3 and because in this vrf it actually gets assigned a VPN label let's call that VPN label 20 so p3 knows that anytime you gets a packet for 20 it knows exactly where that goes it goes down to 81 so that label is communicated on the control plane on the school bus so the school bus which is BGP carries this VPN label for that network across as a as an attribute of the BGP update when p2 gets that it will remember that to reach the 10 network it is going to go ahead and use label 20 as an identifier for it so then we have a happy user the happy user right here sends a trap traffic to the 10 network what p2 is going to do he's gonna say oh the 20 network that is the sorry the 10 network that's the 20 label and it's all pre calculated inside of stuff so it actually attaches the 20 label as the bottom label in this transit packet and this is ok great the 20 label is for the benefit of p3 because when he sees that 20 label he'll know to do with it but now I need to get the traffic over pe3 so p2 is gonna have another label that identifies how to reach PE 3 let's call that label 30 so what's gonna happen is we're gonna have an MPLS packet this is gonna look like this it's gonna have a layer 2 header whether it's you know hdl-c 4 frame relay whatever it is and then at layer 2 and 1/2 so that's the fit one that's - we'll call this 2.5 we're gonna have and then then we have IP below it we're gonna have two labels stuck right in there the bottom label the back most label is gonna say label 20 that's for the benefit of PE 3 and the top label is gonna say 30 that top label as we forward it is gonna be received by this router right here he's gonna say oh that 30 label is how to reach PE 3 he's gonna swap out the 30 and in this case it would be an implicit null so he's gonna actually pop off that label and he's gonna forward the packet to PE 3 who will receive it with just the 20 label P 3 receives it it says oh this transit packet is for the VPN tag of 20 and he knows how to forward that so that's 8 minutes everything you needed to know about multi-protocol label switching and layer 3 VPN in under 10 minutes I am just kidding there's a whole world it's actually very very fascinating and there's lots of great content out there including Cisco's own documentation so thanks for the request on an overview of MPLS I may have over killed that a little bit if you'd like me to focus on specific areas of it let me know how to be happy to do it thanks everybody and have a great great rest of the day [Music] you

Channel: Keith Barker

Views: 421,640

Rating: 4.6891098 out of 5

Keywords: ccie, cisco, ccip, mpls, bgp, multiprotocol label switching, mpls network

Id: MEWIdO40U54

Length: 8min 29sec (509 seconds)

Published: Tue Aug 24 2010