ok ..Label 20 will be on Top(on top of ip header). but why with BoS set to 0? I now that BoS identify identifying label next to the IP header.
On Thu, Apr 8, 2010 at 4:01 PM, venkat <[email protected]> wrote: > Hi, > > 1) when the packet come with label 23, is swapped with label 20..then label > 16 is pushed onto 20 but in LFIB only the top label is showed? > > >>> According to the attachment, the label 23 will be swapped with 16 and a > label 20 (top label, Bos=0) will be pushed as a top label. > > 2) Tag Stack{20 16} .. label 20 will be on top of IP header,BoS set to 1? > so here the frame will look like this : [L3][20,16][L2] ? > > >>>> Label 20 will be on Top. But with Bos= 0. If Bottom of stack (BoS) is > set to 1, then that label is at bottom of the stack. Middle/top label with > have BoS = 0. > Frame looks like as you said [MPLS payload/L3] [20 16] [L2]. > > Thx, > Venkat > http://ippoint.wordpress.com/ > > On Thu, Apr 8, 2010 at 5:22 PM, Marko Milivojevic <[email protected]>wrote: > >> On Thu, Apr 8, 2010 at 11:21, Cristian Nedelcu >> <[email protected]> wrote: >> > i don't understand verry well this part.. so..check out the output from >> > attachment >> > my questions are : >> > 1) when the packet come with label 23, is swapped with label 20..then >> label >> > 16 is pushed onto 20 but in LFIB only the top label is showed? >> > 2) Tag Stack{20 16} .. label 20 will be on top of IP header,BoS set to >> 1? >> > so here the frame will look like this : [L3][20,16][L2] ? >> >> In order to fully answer this, some more context would be nice. Just >> by looking at this output, I would say this is MPLE TE environment >> (I'd venture a guess that it could even be FRR recovery in action), >> with 16 being the tunnel label and 20 the actual label applied for the >> tail-end. The prefix is switched using tunnel label, but tunnel is not >> a physical interface. When the packet gets to the wire, it needs to >> have a "real" label, hence additional label on the stack. >> >> -- >> Marko Milivojevic - CCIE #18427 >> Senior Technical Instructor - IPexpert >> >> YES! We include 400 hours of REAL rack >> time with our Blended Learning Solution! >> >> Mailto: [email protected] >> Telephone: +1.810.326.1444 >> Fax: +1.810.454.0130 >> Web: http://www.ipexpert.com/ >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> > >
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