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Carrier Supporting Carrier with MPLS VPN Customer -- need help posted 07/30/2005
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Hi all,

I need help. I am studying for CCIE Service provider. I am configuring lab with topology on link below:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a0080087cd7.html#xtocid25
My problem is : End-to-end ping is not successful. I do not know why, since I had configured exactly the same with cisco documentation. I had analyzed also LFIB on each LSR, and it seems right. I need someone who is expert in MPLS, to show my mistake in my configuration.


I do ping to 88.88.88.88/32 from CE1. Host 88.88.88.88 is loopback on CE2. Below is the flow of traffic to reach 88.88.88.88 from CE1. (CE1 and CE2 has been configured default route to its each gateway).

PE1#sh tag fo

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 Pop tag 34.34.34.0/24 0 Fa0/1 23.23.23.3

17 Pop tag 3.3.3.3/32 0 Fa0/1 23.23.23.3

18 17 44.44.44.44/32 0 Fa0/1 23.23.23.3

19 18 6.6.6.6/32 0 Fa0/1 23.23.23.3

20 19 7.7.7.7/32 0 Fa0/1 23.23.23.3

22 20 55.55.55.55/32 0 Fa0/1 23.23.23.3

23 21 56.56.56.0/24 0 Fa0/1 23.23.23.3

24 25 67.67.67.0/24 0 Fa0/1 23.23.23.3

29 Untagged 1.1.1.1/32[V] 0 Fa0/0 12.12.12.1

30 Aggregate 12.12.12.0/24[V] 0

34 19 8.8.8.8/32[V] 0 Fa0/1 23.23.23.3

35 19 78.78.78.0/24[V] 0 Fa0/1 23.23.23.3

36 19 88.88.88.88/32[V] 0 Fa0/1 23.23.23.3

PE1#sh ip cef vrf TES 88.88.88.88

88.88.88.88/32, version 28, epoch 0, cached adjacency 23.23.23.3

0 packets, 0 bytes

tag information set

local tag: 36

fast tag rewrite with Fa0/1, 23.23.23.3, tags imposed: {19 29}

via 7.7.7.7, 0 dependencies, recursive

next hop 23.23.23.3, FastEthernet0/1 via 7.7.7.7/32

valid cached adjacency

tag rewrite with Fa0/1, 23.23.23.3, tags imposed: {19 29}

PE1#sh ip bgp v v TES lab
  Network          Next Hop      In label/Out label
Route Distinguisher: 2:200 (TES)
  1.1.1.1/32       12.12.12.1      29/nolabel
  8.8.8.8/32       7.7.7.7         34/27
  12.12.12.0/24    0.0.0.0         30/aggregate(TES)
                   12.12.12.1      30/nolabel
  78.78.78.0/24    7.7.7.7         35/28
  88.88.88.88/32   7.7.7.7         36/29

PE1#sh tag fo det | b 36

36 19 88.88.88.88/32[V] 0 Fa0/1 23.23.23.3

MAC/Encaps=14/22, MRU=1496, Tag Stack{19 29}

0013C3D2ECD90013C3D2E2E38847 000130000001D000

VPN route: TES

No output feature configured

Per-packet load-sharing



** Now packet destined to 88.88.88.88 from CE1 will be tagged with VPN label 29, and IGP label (to 7.7.7.7) 19. Tag stack {19 29} will be sent to CSC-CE1.





CSC-CE1#sh tag fo

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

17 19 44.44.44.44/32 0 Fa0/0 34.34.34.4

18 16 6.6.6.6/32 0 Fa0/0 34.34.34.4

19 21 7.7.7.7/32 42716 Fa0/0 34.34.34.4

20 22 55.55.55.55/32 0 Fa0/0 34.34.34.4

21 23 56.56.56.0/24 0 Fa0/0 34.34.34.4

23 Pop tag 2.2.2.2/32 47317 Fa0/1 23.23.23.2

25 24 67.67.67.0/24 0 Fa0/0 34.34.34.4

CSC-CE1#sh ip cef 7.7.7.7

7.7.7.7/32, version 63, epoch 0, cached adjacency 34.34.34.4

0 packets, 0 bytes

tag information set

local tag: 19

fast tag rewrite with Fa0/0, 34.34.34.4, tags imposed: {21}

via 34.34.34.4, FastEthernet0/0, 0 dependencies

next hop 34.34.34.4, FastEthernet0/0

valid cached adjacency

tag rewrite with Fa0/0, 34.34.34.4, tags imposed: {21}



** CSC-CE will remove label 19 and tag new label 21. Label 21 is label to reach 7.7.7.7. VPN label is not changed, so tag stack become {21 29}, and it is sent to CSC-PE1.



CSC-PE1#sh tag fo

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 25 6.6.6.6/32[V] 0 Fa0/1 45.45.45.5

17 Aggregate 34.34.34.0/24[V] 0

18 Pop tag 23.23.23.0/24[V] 0 Fa0/0 34.34.34.3

19 Aggregate 44.44.44.44/32[V] 26251

20 Pop tag 5.5.5.5/32 0 Fa0/1 45.45.45.5

21 28 7.7.7.7/32[V] 44855 Fa0/1 45.45.45.5

22 24 55.55.55.55/32[V] 0 Fa0/1 45.45.45.5

23 29 56.56.56.0/24[V] 0 Fa0/1 45.45.45.5

24 26 67.67.67.0/24[V] 0 Fa0/1 45.45.45.5

25 Pop tag 3.3.3.3/32[V] 0 Fa0/0 34.34.34.3

28 23 2.2.2.2/32[V] 54742 Fa0/0 34.34.34.3

CSC-PE1#sh ip cef vrf RAS 7.7.7.7

7.7.7.7/32, version 22, epoch 0, cached adjacency 45.45.45.5

0 packets, 0 bytes

tag information set

local tag: 21

fast tag rewrite with Fa0/1, 45.45.45.5, tags imposed: {28}

via 5.5.5.5, 0 dependencies, recursive

next hop 45.45.45.5, FastEthernet0/1 via 5.5.5.5/32

valid cached adjacency

tag rewrite with Fa0/1, 45.45.45.5, tags imposed: {28}



** CSC-PE1 will remove label 21 and change to label 28 based on its LFIB. Label 28 is VPN label. CSC-PE1 need to add IGP label, but since next-hop for 7.7.7.7 is one hop away, it doesn't need to add IGP label. Actually, packet leave CSC-PE1 will be tagged with 3 labels. The inner label is VPN label for Customer Carrier, and Backbone carrier does not undertand at all about this label. After this label, VPN label is tagged. This is VPN label for Backbone carrier. This VPN label is a route destined to Cusctomer carrier network. In this case, VPN label is 28 (to 7.7.7.7). At last, CSC-PE1 needs to add IGP label, which is empty. Tag stack now become {28 29}, and send to CSC-PE2. Tag stack is 2 labels (it should be 3 labes), since IGP label is empty.



CSC-PE2#sh ip cef vrf RAS 7.7.7.7

7.7.7.7/32, version 14, epoch 0, cached adjacency 56.56.56.6

0 packets, 0 bytes

tag information set

local tag: 28

fast tag rewrite with Fa0/0, 56.56.56.6, tags imposed: {21}

via 56.56.56.6, FastEthernet0/0, 0 dependencies

next hop 56.56.56.6, FastEthernet0/0

valid cached adjacency

tag rewrite with Fa0/0, 56.56.56.6, tags imposed: {21}

CSC-PE2#sh tag fo

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 25 3.3.3.3/32[V] 0 Fa0/1 45.45.45.4

18 28 2.2.2.2/32[V] 60085 Fa0/1 45.45.45.4

19 Pop tag 4.4.4.4/32 0 Fa0/1 45.45.45.4

21 18 23.23.23.0/24[V] 0 Fa0/1 45.45.45.4

22 17 34.34.34.0/24[V] 0 Fa0/1 45.45.45.4

23 19 44.44.44.44/32[V] 0 Fa0/1 45.45.45.4

24 Aggregate 55.55.55.55/32[V] 0

25 Pop tag 6.6.6.6/32[V] 0 Fa0/0 56.56.56.6

26 Pop tag 67.67.67.0/24[V] 1710 Fa0/0 56.56.56.6

28 21 7.7.7.7/32[V] 61340 Fa0/0 56.56.56.6

29 Aggregate 56.56.56.0/24[V] 0



** CSC-PE2 will remove IGP label. Since IGP label is untagged from CSC-PE1, it directly remove VPN label (to 7.7.7.7) to be replaced with 21. Label 21 is label for route 7.7.7.7 learned from CSC-CE2. Now, tag stack become {21 29}



CSC-CE2#sh tag fo

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 24 55.55.55.55/32 0 Fa0/0 56.56.56.5

18 22 34.34.34.0/24 0 Fa0/0 56.56.56.5

19 23 44.44.44.44/32 0 Fa0/0 56.56.56.5

20 16 3.3.3.3/32 0 Fa0/0 56.56.56.5

21 Untagged 7.7.7.7/32 91718 Fa0/1 67.67.67.7

22 18 2.2.2.2/32 60907 Fa0/0 56.56.56.5

24 21 23.23.23.0/24 0 Fa0/0 56.56.56.5

CSC-CE2#sh ip cef 7.7.7.7

7.7.7.7/32, version 48, epoch 0, cached adjacency 67.67.67.7

0 packets, 0 bytes

tag information set

local tag: 21

via 67.67.67.7, FastEthernet0/1, 0 dependencies

next hop 67.67.67.7, FastEthernet0/1

valid cached adjacency

tag rewrite with Fa0/1, 67.67.67.7, tags imposed: {}



** CSC-CE2 will remove IGP label 21, and leave it untagged. Now tag stack become {29}



PE2#sh tag for

Local Outgoing Prefix Bytes tag Outgoing Next Hop

tag tag or VC or Tunnel Id switched interface

16 Pop tag 56.56.56.0/24 0 Fa0/1 67.67.67.6

18 Pop tag 6.6.6.6/32 0 Fa0/1 67.67.67.6

19 16 55.55.55.55/32 0 Fa0/1 67.67.67.6

20 18 34.34.34.0/24 0 Fa0/1 67.67.67.6

21 19 44.44.44.44/32 0 Fa0/1 67.67.67.6

22 20 3.3.3.3/32 0 Fa0/1 67.67.67.6

23 22 2.2.2.2/32 0 Fa0/1 67.67.67.6

26 24 23.23.23.0/24 0 Fa0/1 67.67.67.6

27 Untagged 8.8.8.8/32[V] 0 Fa0/0 78.78.78.8

28 Aggregate 78.78.78.0/24[V] 0

29 Untagged 88.88.88.88/32[V] 0 Fa0/0 78.78.78.8

PE2#sh ip cef vrf TES 88.88.88.88

88.88.88.88/32, version 18, epoch 0, cached adjacency 78.78.78.8

0 packets, 0 bytes

tag information set

local tag: 29

via 78.78.78.8, 0 dependencies, recursive

next hop 78.78.78.8, FastEthernet0/0 via 78.78.78.8/32

valid cached adjacency

tag rewrite with Fa0/0, 78.78.78.8, tags imposed: {}



** PE2 will remove tag 29, and leave untagged. And now, untagged packet is successful sent to CE2.



I do not see something wrong with LFIB and the traffic flow. But, why end-to-end ping is not success?? I put access-list on CE2, but there is not logged for icmp. It prove that icmp packet never reach destination.

Thanks for your help,
Firebat