RE: MPLS Aggregate label

Implicit Null, why should the router upstream pop one label and impose
another when it is destined for the next hop. So instead it does a PHP
Penultimate Hop Pop. It removes the local label and doesn't push another.
Saving some resource, most likely very minimal, but just enough to make it
so that the P router could continue on supporting all the directly connected
PE's.

Explicit Null's need to be configured so that Null Label is installed.

I believe an aggregate label is a per VRF label, so the PE just advertises a
single label for all prefixes that belong to that VRF. The receiving PE will
need to do a local IP lookup to determine which interface the packet needs
to be forwarded on.

David

--
http://dcp.dcptech.com
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> Aaron
> Sent: Wednesday, March 09, 2011 3:44 PM
> To: 'CCIE KID'; 'Cisco certification'
> Subject: RE: MPLS Aggregate label
> 
> Just saw this in my lab today...  imp-null seems to have some
> correlation to
> connected routes....  perhaps someone can shed some light on this
> fact/observation...
> 
> R6#sh mpls ip binding
>   10.10.10.0/24
>         in label:     imp-null
>   140.100.0.0/27
>         in label:     24
>   140.100.0.32/27
>         in label:     23
>   140.100.0.64/28
>         in label:     20
>   140.100.0.84/30
>         in label:     22
>   140.100.0.88/30
>         in label:     21
>   140.100.1.0/24
>         in label:     25
>   140.100.2.0/24
>         in label:     imp-null
>   140.100.3.0/24
>         in label:     imp-null
>   151.100.0.0/15
>         in label:     34
>   172.16.0.0/16
>         in label:     26
>   192.128.128.0/24
>         in label:     19
>   199.199.1.0/24
>         in label:     29
>   199.199.2.0/24
>         in label:     28
>   199.199.3.0/24
>         in label:     27
>   199.199.4.0/24
>         in label:     33
>   199.199.5.0/24
>         in label:     32
>   199.199.6.0/24
>         in label:     31
>   199.199.7.0/24
>         in label:     30
>   199.199.8.0/24
>         in label:     18
>   199.199.9.0/24
>         in label:     17
>   199.199.10.0/24
>         in label:     16
> R6#
> R6#
> R6#
> R6#sh ip ro con
> R6#sh ip ro connected
>      140.100.0.0/16 is variably subnetted, 8 subnets, 4 masks
> C       140.100.2.0/24 is directly connected, FastEthernet0/0
> C       140.100.3.0/24 is directly connected, FastEthernet0/1
>      10.0.0.0/24 is subnetted, 1 subnets
> C       10.10.10.0 is directly connected, Ethernet4/0
> R6#
> 
> 
> -----Original Message-----
> From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
> CCIE
> KID
> Sent: Wednesday, March 09, 2011 5:18 AM
> To: Cisco certification
> Subject: MPLS Aggregate label
> 
> Hey what is the difference between Aggregate label ,implicit null and
> explicit null label in MPLS
> 
> 
> --
> With Warmest Regards,
> 
> CCIE KID
> IN PURSUIT OF CCIE
> 
> 
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