Home » MPLS


What is 6PE?

6PE is one of the efficient solutions for interconnecting IPv6 islands over an IPv4-only MPLS cloud without needing to drastically change the core network design by having all your Core routers dual-stacked 6PE does not use manual standard tunnels, it provides an alternative where all tunnels are established dynamically eliminating the need to configure and maintain tunnels. The approach requires that the edge routers connected to IPv6 islands be Dual Stack Multiprotocol-BGP-speaking routers. while the core routers can only run IPv4 MPLS Configuring 6PE is has a lot of similarities with configuring  IPv4 VPNs as both use MP-BGP to distribute non-IPv4 reachability …

Read More »

MPLS Label Distribution: LDP Part3

So far so good, we have finished two parts of LDP and in this post we are going to explore another function of the four major functions of LDP. After an LDP session is initialized, LDP peers start to exchange label mappings according to the pre-negotiated parameters. In this post I will assume that LDP is using the most common label distribution modes for as follows: MPLS Label Space: Per platform label space. MPLS label retention mode: Liberal label retention. MPLS Label distribution mode: unsolicited downstream. MPLS Label control mode: Independent label distribution.

Read More »

MPLS Label Distribution – LDP Part2

In my previous post I listed the main four functions of the label distribution protocol LDP and explained some concepts. In this post lets start dealing with the first two functions: Automatically discover LDP Peers in the same network segment. Establish and maintain LDP sessions with those peers. But I am not going to reinvent the wheel because I have already covered the two functions in older posts please have a look at them: LDP neighbor discovery, session establishment and maintenance. What is LDP extended discovery? We will soon do the next part, see you then.

Read More »

MPLS Label Distribution – LDP Part1

MPLS Label distribution protocol (LDP) as its name implies was defined to automatically create and maintain Label switched paths (LSP) in an MPLS network via label distribution. LDP specifications are defined in RFC 5036. In brief LDP assigns local label bindings to all IGP routes in the routing table and forms neighbor relationships with other LDP peers to exchange those local bindings. I will explain this further below. Label distribution Protocol (LDP) has four major functions as listed below: Automatically discover LDP Peers in the same network segment. Establish and maintain LDP sessions with those peers. Exchange and advertise label …

Read More »

The Role of BGP in MPLS networks

In almost every book you will read about MPLS, the author will state that one of the MPLS benefits is having a BGP free core network; sometimes they explain it sometimes not. However, to really understand this statement I encourage you to imagine removing MPLS from your core network and see what adjustments you need to do in order to get the transit traffic to its destination. Do this  just in your mind’s eye please 🙂 If you are not willing to do this I will try in this post to bring the picture closer to you. Lets first examine …

Read More »

MPLS Label Operations

In my previous post I explained what MPLS is and how it works from a high level perspective. In this post I will explain MPLS label operations and how labeled packets are processed in MPLS networks. When a labeled packet is received the label value at the top of the stack is examined to determine two things: The next hop and the exit interface to which the packet is to be forwarded. The operation to be performed by the LSR on the label stack before forwarding the packet. Listed below are the operations performed by the LSR on the MPLS …

Read More »