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

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>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 is locally connected, and the "next hop"
> is this router itself.
> The 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
>> >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 0 Se0/0 point2point
>>> 17 Pop tag 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 is network between R6 and CE router.
>>>
>>> Topology
>>> ---(R5)----(R6)----(CE)
>>>
>>> R6 Lo : 11.1.6.6/32
>>> R6/CE : 11.1.68.0/24
>>>
>>> --
>>> /Lefe Meedorf/
>>>
>>>
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>>
>>
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>>
>>
>>
>>
> --
> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina
>
>
>
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>
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Received on Sun Dec 26 2010 - 15:11:13 ART