RE: Difference between Aggregate and Implicit Null

I'll try to be clear, but only conveying what I'm learning and seeing as I
gain an understanding of this myself...

I'm seeing in my lab the following...

- imp-null for FEC (ip routes) that are directly connected
--- look at the output below, all my local bindings for connected ip routes
in global (non-vrf) routing table result in imp-null entries....which I
believe have a label value of 3...

- Aggregate (as I believe someone mentioned the other day (perhaps in a
ucast email to me, can't remember)) appears to be related to VRF/VPN FEC
(routes), and appears to be directly connected VRF routes.
--- look at the output below, my one and only vrf route that is directly
connected is the only one with Aggregate

************************
*** imp-null example ***
************************

********* a pe lsr **********

d3#sh mpls ldp bindings local
  tib entry: 140.1.1.1/32, rev 2
        local binding: tag: imp-null
  tib entry: 140.1.1.2/32, rev 10
        local binding: tag: 18
  tib entry: 140.1.2.0/29, rev 16
        local binding: tag: imp-null
  tib entry: 140.1.2.8/29, rev 6
        local binding: tag: 16
  tib entry: 140.1.2.16/29, rev 8
        local binding: tag: 17

d3#sh ip ro connected
     140.1.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 140.1.1.1/32 is directly connected, Loopback0
C 140.1.2.0/29 is directly connected, FastEthernet0/0

****** a p lsr ************

d4#
d4#
d4#sh mpls ld bin local
  lib entry: 140.1.1.1/32, rev 6
        local binding: label: 16
  lib entry: 140.1.1.2/32, rev 8
        local binding: label: 17
  lib entry: 140.1.2.0/29, rev 2
        local binding: label: imp-null
  lib entry: 140.1.2.8/29, rev 4
        local binding: label: imp-null
  lib entry: 140.1.2.16/29, rev 10
        local binding: label: 18
d4#
d4#sh ip ro conn
     140.1.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 140.1.2.8/29 is directly connected, GigabitEthernet0/1.200
C 140.1.2.0/29 is directly connected, GigabitEthernet0/1.100
d4#

*************************
*** aggregate example ***
*************************

d3#sh mpl for
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 Pop tag 140.1.2.8/29 0 Fa0/0 140.1.2.2
17 18 140.1.2.16/29 0 Fa0/0 140.1.2.2
18 17 140.1.1.2/32 0 Fa0/0 140.1.2.2
19 Aggregate 3.3.3.0/30[V] 1052584

d3#sh ip route vrf test connected
     3.0.0.0/30 is subnetted, 1 subnets
C 3.3.3.0 is directly connected, FastEthernet0/1
d3#

***** the pe router on the other side of the lab net *******

d6#sh ip cef vrf test 3.3.3.0
3.3.3.0/30
  nexthop 140.1.2.17 GigabitEthernet0/2 label 18 19

d6#sh ip cef vrf test 3.3.3.0 de
3.3.3.0/30, epoch 0
  recursive via 140.1.1.1 label 19
    nexthop 140.1.2.17 GigabitEthernet0/2 label 18

d6#sh mpls for
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or VC or Tunnel Id Switched interface
16 Pop Label 140.1.2.8/29 0 Gi0/2 140.1.2.17
17 18 140.1.1.1/32 0 Gi0/2 140.1.2.17
18 17 140.1.2.0/29 0 Gi0/2 140.1.2.17
19 No Label 6.6.6.0/30[V] 1153794 aggregate/test
d6#

d6#sh ip ro vrf test bgp

Routing Table: test
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
       D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
       N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
       E1 - OSPF external type 1, E2 - OSPF external type 2
       i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
       ia - IS-IS inter area, * - candidate default, U - per-user static
route
       o - ODR, P - periodic downloaded static route, + - replicated route

Gateway of last resort is not set

      3.0.0.0/30 is subnetted, 1 subnets
B 3.3.3.0 [200/10] via 140.1.1.1, 17:23:18
d6#

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Routing Freak
Sent: Friday, March 11, 2011 4:37 AM
To: Cisco certification
Subject: Difference between Aggregate and Implicit Null

Can anyone tell me clearly the difference between Aggregate and Implicit
null label??

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Received on Fri Mar 11 2011 - 08:29:49 ART