Hi,
A local label (or tag) is allocated for each prefix learned via your IGP and inserted in the LFIB (label forwarding information base) when using LDP - they're then also distributed using that same protocol. When a labeled packet is _received_ by the LSR it checks the LFIB for the local label and does an operation (push, pop, swap, etc.) based on that. Do show mpls forwarding-table somewhere you have working LDP and you'll see how it works - check out the two first columns (local tag, outgoing tag). In larger networks or if you're good at housekeeping you usually want to limit the amount of local labels allocated just to the PE loopbacks so one then uses label filtering to suppress the rest. Assuming everything carried by BGP is set NHS things will work great. Imposing a label usually equals a label push operation (add a label) which happens on egress on the LSR. HTH :) Kaj > From: "Bodnar, Edward" <[email protected]> > Date: Tue, 4 Aug 2009 11:01:33 -0700 > To: <[email protected]> > Subject: [OSL | CCIE_RS] MPLS > > Having trouble understanding the difference between a local tag and an imposed > tag. > > Can anybody explain the difference. I thought the local tag was the tag you > were imposing but I am finding out this is not true. > >
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