Difference between the BGP LSP and LDP LSP

Latest reply: Feb 14, 2020 16:01:55 169 2 3 0

Some guys may have noticed that there are more than one types of LSP in the result displayed on the MPLS L3VPN PE router. Just as the picture below shows:


Some guys might be curious about the new LSP, in this post, we’ll introduce difference between them.


First, let’s take a look at LDP LSP. It’s the most commonly used LSP in the MPLS tunnel. The LDP protocol distributes the labels for the different FEC (We have introduced before, click here to learn more). The routers keep the labels and form a LSP(label switching path) between the source device and destination device. It should be pointed out that the LSP is more like a single path, when a labeled packet is generated, the forwarding path is formed, it sounds like the whole life is freezen when a baby was born.

BGP LSP is a special LSP. Unlike the LDP LSP has a clearly forwarding path, BGP LSP is more like a virtual path. It only has an entrance and the exit. When the packets are forwarded in the BGP LSP, it feels like the packets are jumping between the source and destination, the packet enters into the BGP LSP,  and comes out from the BGP LSP directly, no other routers contained in this process.

Actually, there is another LSP, which is MPLS TE LSP. It’s more like the LDP LSP, the only differece is the distribution protocol is RSVP-TE, rather than LDP.


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Created 6 days ago Helpful(0) Helpful(0)

Well Explained
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Created 5 days ago Helpful(0) Helpful(0)

this can be a very good interview question, thanks for sharing.
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