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
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