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I am learning about MPLS at the moment. I know that routers in general make forwarding decisions based on the destination IP addresses and available routes in the routing table.

However, with MPLS it's different. MPLS uses labels.

Why does MPLS uses labels instead of destination IP addresses when making forwarding decisions?

Thank you in advance!

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  • because the protocol that uses destination IP addresses to make forwarding decisions is called IP and not called MPLS? Dec 8, 2022 at 14:41
  • My point was that why are labels used for routing in an MPLS infrastructure and not the destination IP addresses?
    – Mitrixsen
    Dec 8, 2022 at 14:52
  • because if they were, it would be an IP network and not an MPLS network. I don't understand the question. Are you asking why people use MPLS? Dec 8, 2022 at 14:55

2 Answers 2

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I think what you're really asking is, "Why use MPLS instead of traditional routing?"

One of the major reasons (probably the reason) people use MPLS is address independence. You can have two customers with the same IP address ranges, yet keep them completely separate and independent.

MPLS can also be used with other non-routed (i.e, layer 2) protocols. This flexibility is one of the most important features of MPLS.

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It's MPLS, Multi-protocol Label Switching. The entire point of it is to switch multiple protocols based on their label. It doesn't even have to be IP traffic involved, it can be ATM or something instead. The label switching is the definition of the platform. What you are asking is like asking, "Why does a gasoline internal combustion engine use gasoline and oxygen to power its internal combustion?" Because it is designed to function that way. If it were designed to function another way, then it would be called something else.

If you want to know why MPLS would be useful in a given situation, you have to just read about its features to see how it could be helpful to an organization. For what it's worth, MPLS is largely being replaced by SD-WAN these days because SD-WAN can do similar things with less specialized equipment and with more features and integration with external controls and management platforms.

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