when i was reading a book i got into some thing Router Alert Label

any details for the rotuer alert label 

as per my reading : 

The Router Alert label is the one with value 1. This label can be present anywhere in the label stack except at the bottom. When the Router Alert label is the top label, it alerts the LSR that the packet needs a closer look


what inspection is been done and how at LSR




  • Well the above explains it pretty well. Router alert is used to tell an LSR that it needs to examine the packet itself. For example MPLS traceroute uses router alert label to find all the LSRs along the LSP.

    Basically when a CEF enabled router receives a labeled packet, it only goes through the LFIB and is label switched without any further actions from the control plane. When a router alert label is set, the packet is lifted up to the control plane and examined closer. There may be dozens of different reasons why this would be used, traceroute being one of those.

  • Good example to make it understand 

    thanks jent 

    and once again congrats for great achievement

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