MPLS Label Duplication in the MPLS ring

[network_geek]

Hi All,

I am wondering how does a network work around one MPLS label that gets generated on multiple devices. Is that a bad omen for your network or is it completely fine? If it is a completely fine phenomenon then how does the packet switching take place in the Core?

Thanks in advance.

[Harold Ritter]

Hi @network_geek ,

In the case of LDP, the label is only locally significant to the router who generates and advertises it. So each router in the core can generate the same label without any problem.

Regards,

[paul driver]

Hello

Adding on to what @Harold Ritter has stated, this label space can be manually changed, and if remember right you need a reload of the PE/P rtr to do so

conf t
mpls label range xxx yyy
sh mpls label range

[mlund]

Also added to what Harold and Paul wrote. How is the packet switching take place

Each router looks in its routing table and for every route, it assigns a label (you can decide wich routes should have a label)

Then it sends a ldp update to neighbors saying, for prefix A use label X, for prefix B use label Y and so on.

It also receives update from neighbors, so it starts building an label switching database, so if a neigh on ethernet1/1 sends a update containing, for prefix A use label E, and for prefix B use label F, it will put in the database

Incomng label X outgoing label E outgoing interface ethernet1/1

incoming label Y outgoing label F outgoing interface ethernet 1/1

This means that if a packet arrives on an interface (not ethernet1/1) with the label X the router swaps that label to label E  and sends in out on eternet1/1

/Mikael

[network_geek]

Hi All,

Thank you all for updating me with your knowledge. I have grasped what was required. Thank you all very much!