In previous example a CE-PE routing protocol was BGP, but it’s not only option. We can also use IGP protocols like OSPF. We use this protocol for customers in VRF_A. On PE router OSPF is redistributed to iBGP and vice versa, otherwise vpnv4 routes won’t be propagated through MPLS domain. MPLS VPN area is usually referred as super backbone and PE routers are ASR routers.
Because of redistribution in normal OSPF operation those routes would be treated as external routes (LSA Type 5) when redistributed back to OSPF. PE router is treated as ASBR. When redistributing from MP-BGP back to OSPF those routes are marked as inter-area routes (LSA Type 3), even if the area numbers on both ends does not match. However if customer network has more than one area PE routers must be in area 0 or virtual-link between PE router and nearest ABR must be configured.
Our network is now able to carry vpnv4 prefixes, so it’s now time to receive them from customers. As mentioned before vpnv4 prefix consist of route distinguisher (RD) and IPv4 prefix. But that’s not all. We have to have set of tools to differ one customer from another and control propagation of prefixes. Those tools are VRFs, RDs and RTs. Read More →
Our core network after first chapter of workshop is able to forward labeled packets. Let’s focus now on deploying some services within this network. First MPLS L3VPN. As for now we have IS-IS as an IGP protocol in the core to forward prefixes of links and loopbacks, and LDP to maintain label exchange. Next step is to introduce mechanism that will allow us to attach label information to prefixes. MP-BGP is an extension of standard BGP protocol that let us carry MPLS VPN routes. It’s flexible and well known protocol. At this step we configure core routers (P and PE) to carry MPLS VPN routes. Read More →
This is the first post in a series where I’ll be presenting various aspects of MPLS network. Starting from basics and moving forward to more advanced topics. We’ll be using following topology:
As you can see we have two P routers, three PE routers, four CE routers and one of PE routers will also act as BGP route reflector. Different MPLS L3VPN networks are using different CE-PE protocols. Every router have Loopback0 interface configured with address 10.0.0.x/32 where x is the router number. Subnets on links between routers are addressed in scheme known from CCIE workbooks, that third octet shows between what routers link is configured and fourth octet represents router number. So if we are talking about link between R4 and R5 the address on R4 E0/1 interface is 10.0.45.4/24 and on R5 E0/1 interface 10.0.45.5/24. Read More →
There are four cases when summarization shouldn’t be used in MPLS Backbone:
MPLS-enabled ATM network
Transit BGP where core routers are not running BGP
So those are the cases where end-to-end LSPs are required. Let’s look why. Read More →
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