What does PE-CE mean in the context of MPLS ? What is CE , P and PE device in MPLS and MPLS VPN ?
These are foundational terms and definition in MPLS.
MPLS is one of the most commonly used encapsulation mechanism in Service Provider networks and before studying more advanced mechanisms, this article is must read.
In order to understand PE-CE, we need to understand first what are PE and CE in MPLS.
Let’s take a look at below figure.
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Figure -1 MPLS network PE, P and CE routers
In Figure-1 MPLS network is shown. This can be an Enterprise or Service Provider network. MPLS is not only a service provider technology. It can provide segmentation/multi tenancy for the enterprise environment as well.
Three different types of router are shown. CE , PE and P routers.
CE devices are located in the customer site. PE and P devices are located in the Service Provider site.
If it is Enterprise network, WAN routers can be considered as PE routers, and the switches can be a CE devices.
PE routers don’t have to be connected to P routers. PE routers can be directly connected to each other.
CE devices don’t run MPLS. PE devices run both IP and MPLS. P devices don’t run IP but only MPLS.
You find above sentence everywhere when you study MPLS. It actually means, CE devices don’t switch the MPLS label to function.
PE devices, when packet arrives first lookup IP destination address and then uses MPLS label to function.
P devices don’t do IP lookup at all but only switch MPLS labels. Otherwise P devices of course have IP addresses on their interfaces as well.
In MPLS, service can be Layer 2 or Layer 3.
In Layer 3 MPLS VPN, IP routing is enabled between PE and CE devices.
Routing protocols in theory can be Static Routing, RIP, EIGRP, OSPF, IS-IS and BGP.
All of them are IETF standard. But in real life, most service providers only provide Static Routing and BGP as a PE-CE routing protocol.
PE-CE interface is only IP and not MPLS. Specific application of PE-CE as MPLS is called CSC (Carrier Supporting Carrier). But in basic MPLS Layer 3 MPLS VPN, PE-CE link is always IP.
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