exactly what I said. BoS set to 1 just for that label located near the IP header.
On Thu, Apr 8, 2010 at 4:32 PM, venkat <[email protected]> wrote: > Just to clarify.. MPLS labels (stack/single label) will be inserted between > L2 and L3. > so, in case of IP packets encapsulated in MPLS, the packet should look > like, > > PHY-- L2 header(source/ destination MAC etc)----- MPLS label stack > [label1:label2:label3]------------ L3 header (Source/Des IP) > > in the above format, only Lable3 will have Bos set to 1, indicating it is > on bottom of the stack and all other labels have Bos = 0. (we can have any > number of labels and the point is the last label-bottom- will have Bos =1) > > Am i clarified you? > > Thx, > Venkat > > On Thu, Apr 8, 2010 at 6:39 PM, Cristian Nedelcu < > [email protected]> wrote: > >> 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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