Re: Simple MPLS : Difference between "untagged" and "pop tag"

Hmm, no.
Explicit-null would actually use the null (0) tag on the last MPLS hop.
Explicit-null will just show as 0, AFAIK.

-Carlos

George Goglidze wrote:
> I can't check it right now, but I think "explicit-null" label would
> indicate "Untagged" as well in the LFIB.
> Please correct me if I'm wrong.
>
> Regards,
>
> On Sun, Dec 26, 2010 at 2:05 PM, Carlos G Mendioroz <tron_at_huapi.ba.ar
> <mailto:tron_at_huapi.ba.ar>> wrote:
>
> Pop tag means that the destination (network) is connected to a LSR,
> i.e., a router that this router knows that supports MPLS.
> This may be because he is receiving LDP from it indicating
> "implicit-null" as the tag for this prefix.
>
> Untagged means that the destination is known by some means (routing
> protocol?) but the next hop is not MPLS aware (this router is not
> receiving MPLS tag info for this prefix) so it will remove the stack
> before forwarding.
>
> In your example, the 11.1.68.0/24 <http://11.1.68.0/24> is locally
> connected, and the "next hop" is this router itself.
> The 11.1.6.6/32 <http://11.1.6.6/32> is connected to another router
> and there is no tag info
> for this prefix. May be the loopback is a /24 ?
>
> -Carlos
>
>
> Manouchehr Omari wrote:
>
> Pop tag means remove the top label and send the remaining payload.
> Untagged means the outgoing interface is not MPLS enabled remove
> the label
> and send the packet without label.
>
> I recommend you to read "MPLS Fundamentals" which cover these
> tips in
> detail.
>
> HTH
>
>
> On Sat, Dec 25, 2010 at 9:33 PM, Lefe Meedorf
> <feeldefreedom_at_gmail.com <mailto:feeldefreedom_at_gmail.com>>wrote:
>
> Hi,
>
> In my simple MPLS setup, I see following entires in "LFIB".
>
> R5#show mpls forwarding-table
> Local Outgoing Prefix Bytes tag Outgoing
> Next Hop
> tag tag or VC or Tunnel Id switched interface
> 16 Untagged 11.1.6.6/32 <http://11.1.6.6/32> 0
> Se0/0 point2point
> 17 Pop tag 11.1.68.0/24 <http://11.1.68.0/24> 0
> Se0/0 point2point
>
> What is the difference between "Untagged" and "Pop tag" ?
> 11.1.6.6 is R6 (i.e. PE) Loopback 0.
> 11.1.68.0/24 <http://11.1.68.0/24> is network between R6 and
> CE router.
>
> Topology
> ---(R5)----(R6)----(CE)
>
> R6 Lo : 11.1.6.6/32 <http://11.1.6.6/32>
> R6/CE : 11.1.68.0/24 <http://11.1.68.0/24>
>
> --
> /Lefe Meedorf/
>
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> Carlos G Mendioroz <tron_at_huapi.ba.ar <mailto:tron_at_huapi.ba.ar>>
> LW7 EQI Argentina
>
>
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-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net