This Lab is a mixture of Service provider and Enterprise infrastructure technologies. From the SP side, I configured MPLS, L3VPN, Inter-AS L2VPN, EBGP, and OSPF as the IGP, LDP to ensure label distribution, and Route Reflector.
On the Enterprise Infrastructure side, I made use of a bunch of important technologies like DMVPN phase 3 to ensure connectivity between branches over MPLS/Internet (underlay), EIGRP name mode as the IGP, IPSEC, route redistribution, etc.
Topology
SP Network PART - I
1- IGP and MPLS configuration
As you may know in the SP network it is necessary to have an interior Gateway Protocol (IGP) to ensure that all nodes are reachable and be able to exchange routing information, which is also a prerequisite for MPLS. In this lab, I use the most popular IGP (OSPF), and one of the good things about OSPF it gives us the ability to enable LDP automatically in all interfaces that are participating in the OSPF routing process. If you remember the section where I spoke about MPLS, It is mentioned that in an MPLS network the forwarding decision is based on the label’s information instead of the destination IP address like traditional routing does, and to be able to do that MPLS use Label Distribution Protocol (LDP) to distribute the label’s information over the IP network.
BUT WHY MPLS?
With MPLS when a packet just arrives in the incoming interface of a router instead of processing the whole IP header and making a lookup into the Forwarding Information Base (FIB) commonly known as the routing table to find the best route for the Destination IP address (traditional routing) only the label is checked and that is sufficient to forward the packet. By doing that the router simply forwards the packet without analyzing it, and at the end of the day it doesn’t know the actual content of the packet, it doesn’t know whether it is an IP packet, an IPv6 packet, or simply an Ethernet frame with a label attached to it, and that opens a bunch of possibilities to transport a lot of different kind of technologies or protocols over an MPLS network and this is what we call Any transport over MPLS (AToM).
Service Providers love MPLS because by using it they don´t have to have different Backbones for each type of service or technology anymore (as they used to do in the past), now they can have a single IP Infrastructure with MPLS enabled and be able to deliver all different kind of services, such as Layer 2&3 VPN.
HOW TO ENABLE MPLS?
There are 2 ways to do it, you can enable MPLS manually in an interface with the command mpls ip under the interface configuration mode, sincerely this method is quite used since it requires a lot of work from an administration perspective (administration overhead). The best approach is to enable it in the routing process of the IGP with the command mpls ldp autoconfig under de routing process of OSPF in this case. This command will enable MPLS in all the uplinks and downlinks participating in the OSPF process.
Another optional and useful command I use here but that’s not so relevant in a production environment is the mpls label range, it helps me have control over the label assigned by each mpls router since the labels are locally significant.
SPs ROUTERS CONFIG
- Verification
Now we verify that the IGP is running properly by checking the routing table, we also confirm that all the destination networks have at least one label assigned to them by getting a look at the MPLS Forwarding table, and finally we verify the neighboring relationship between MPLS routers that facilitates the exchange of label’s information.
SP Services PART - II
Now we have routing and MPLS running properly in the SP networks, it’s time to get the SP infrastructure ready to deliver the most popular services customers usually ask for, and to prepare the infrastructure to be part of the global network (internet) by exchanging routing information with other SPs via eBGP.
Coming soon !!!!
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