I took an MPLS course online and it pointed something out I really didn't get, or at least need clarification on.
The person giving the course said that because of how the PE's interact with the P LSR's that is isn't necessary to run a routing protocol in the core on the P's and that savings in resource is a reason to go to MPLS.
Can I get some clarification?
Do the P MPLS LSR's rely only on labels for routing or are they running a routing protocol in the background?
Reza is actually incorrect when he says that the P router runs BGP, P routers only run MPLS and the Core IGP which it uses to perform packet forwarding updates between PE routers, and in most cases a Route Reflector.
Here is a quick decription of each element of a Service Provider IP/MPLS network:
P Router - A better term is Label Switch Router (LSR) which is a featureless box with the primary purpose of Label Switching and passing IGP routing updates for MP-BGP routing between PE routers.
PE Router - Provider Edge Router, which by its name is at the aggregation layer of the MPLS Core. This is where Customer Edge routers terminate their peering (whatever PE-CE protocol is selected). These routers run MultiProtocol BGP between each other PE router and Route Reflector (if its in the design) to exchange VPNV4 routing (VPN routes) between PEs.
CE Router - Customer Edge Router, is the Customers CPE or WAN Edge router.
If you are intested in learning more on MPLS, I recommend you read the Cisco Press book "MPLS Fundamentals" by Luc De Ghein.
Introduction: The "external-out enable" command is available for
configuration under the "router ospf process" in case of the IOS-XR
operating system. This command basically enables advertisement of
intra-area routes on the device as external routes in th...
Introduction Basic configuration for netflow Scale parameters for
netflow Netflow support Architecture Packet flow for netflow Inside the
LC CPU Netflow Cache size, maintenance and memory Sample usage Cache
Size Aging Permanent cache Characteristics Which...