Hi,
After watching the video I build the lab my self-according to the same diagram used in the video with the exact same setup. I tried to follow the movie as much as possible to learn the technology. I started with the configuration where the traffic still flows over the route reflector so the ebgp peers still are changing the next-hop vaue. That is where my issueis. The control plane is correct I received all routes in all VRF’s The dataplane for VRF B and C is also correct because I can reach the loopback addresses within the VRF. However the dataplane of VRF A is not working. I cannot reach the loopback address. I have researched the issue and found out where the problem is and how I can resolve it. However I failed to figure out exactly why this behavior is like this so maybe you can help me out here.
I have enable: debug mpls packet on all IOS routers and found out that the path from R10 to R8 is okay the ICMP packets arrived at R8
R10#ping 8.8.8.8 source lo 1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 8.8.8.8, timeout is 2 seconds:
Packet sent with a source address of 10.10.10.10
.....
Success rate is 0 percent (0/5)
R8#
*May 15 08:38:12.787: ICMP: echo reply sent, src 8.8.8.8, dst 10.10.10.10, topology BASE, dscp 0 topoid 0
R8#
*May 15 08:38:14.787: ICMP: echo reply sent, src 8.8.8.8, dst 10.10.10.10, topology BASE, dscp 0 topoid 0
R8#
*May 15 08:38:16.789: ICMP: echo reply sent, src 8.8.8.8, dst 10.10.10.10, topology BASE, dscp 0 topoid 0
R8#
*May 15 08:38:18.794: ICMP: echo reply sent, src 8.8.8.8, dst 10.10.10.10, topology BASE, dscp 0 topoid 0
R8#
*May 15 08:38:20.793: ICMP: echo reply sent, src 8.8.8.8, dst 10.10.10.10, topology BASE, dscp 0 topoid 0
R8#
At the debug mpls packet on R6 I can see the traffic returning from R8, XR2 did not send a transport label
R6#
*May 15 08:40:33.025: MPLS les: Et0/0.196: rx: Len 1514 Stack {16 0 251} {16001 0 254} - ipv4 data s:10.10.10.10 d:8.8.8.8 ttl:254 tos:0 prot:1
*May 15 08:40:33.025: MPLS les: Et0/0.206: tx: Len 1510 Stack {16001 0 250} - ipv4 data s:10.10.10.10 d:8.8.8.8 ttl:254 tos:0 prot:1
*May 15 08:40:33.027: MPLS les: Et0/0.206: rx: Len 1514 Stack {25 0 254} - ipv4 data s:8.8.8.8 d:10.10.10.10 ttl:254 tos:0 prot:1
R6#
*May 15 08:40:35.027: MPLS les: Et0/0.196: rx: Len 1514 Stack {16 0 251} {16001 0 254} - ipv4 data s:10.10.10.10 d:8.8.8.8 ttl:254 tos:0 prot:1
*May 15 08:40:35.027: MPLS les: Et0/0.206: tx: Len 1510 Stack {16001 0 250} - ipv4 data s:10.10.10.10 d:8.8.8.8 ttl:254 tos:0 prot:1
*May 15 08:40:35.029: MPLS les: Et0/0.206: rx: Len 1514 Stack {25 0 254} - ipv4 data s:8.8.8.8 d:10.10.10.10 ttl:254 tos:0 prot:1
When I look into the vpnv4 table on XR2 I can see it is using a VPN label 25 with a next-hop of 2.2.2.2
RP/0/0/CPU0:XR2#sh bgp vpnv4 unicast vrf A 10.10.10.10
BGP routing table entry for 10.10.10.10/32, Route Distinguisher: 100:1
Versions:
Process bRIB/RIB SendTblVer
Speaker 337 337
Local Label: 16009
Last Modified: May 14 07:23:21.885 for 00:03:37
Paths: (1 available, best #1)
Advertised to peers (in unique update groups):
5.5.5.5
Path #1: Received by speaker 0
Advertised to peers (in unique update groups):
5.5.5.5
1
2.2.2.2 (metric 1) from 2.2.2.2 (2.2.2.2)
Received Label 25
Origin incomplete, localpref 100, valid, external, best, group-best, import-candidate, imported
Received Path ID 0, Local Path ID 1, version 337
Extended community: OSPF domain-id:0x5:0x000000020200 OSPF route-type:0:2:0x0 OSPF router-id:10.10.104.4 RT:100:1
Source VRF: A, Source Route Distinguisher: 100:1
RP/0/0/CPU0:XR2#
When I look into the forwarding table I noticed that destination 2.2.2.2 has pop as outgoing label to 6.6.6.6 so it indeed does not send a transport label. This is what I cannot figure out why this is
RP/0/0/CPU0:XR2#sh mpls forwarding
Wed May 14 07:29:50.367 UTC
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
16000 Aggregate A: Per-VRF Aggr[V] A 0
16001 Unlabelled 8.8.8.8/32[V] Gi0/0/0/0.208 10.10.208.8 81840
16002 Pop 6.6.6.6/32 Gi0/0/0/0.206 10.10.206.6 6830
16003 Pop 10.10.56.0/24 Gi0/0/0/0.206 10.10.206.6 0
16004 Pop 10.10.196.0/24 Gi0/0/0/0.206 10.10.206.6 0
16005 18 5.5.5.5/32 Gi0/0/0/0.206 10.10.206.6 7370
16006 17 19.19.19.19/32 Gi0/0/0/0.206 10.10.206.6 0
16007 Pop 2.2.2.2/32 Gi0/0/0/0.206 10.10.206.6 3215
16008 20 4.4.4.4/32 Gi0/0/0/0.206 10.10.206.6 4860
16009 25 10.10.10.10/32[V] 2.2.2.2 1040
16010 26 10.10.104.0/24[V] 2.2.2.2 0
16011 21 100:2:10.10.115.0/24 \
5.5.5.5 0
16012 22 100:2:11.11.11.11/32 \
5.5.5.5 0
16013 23 100:3:10.10.125.0/24 \
5.5.5.5 0
16014 24 100:3:12.12.12.12/32 \
5.5.5.5 0
When I look into R6 MPLS forwarding table it does not say it is local but has a local label of 19 (so why is XR2 not have label 19 into its forwarding table)
R6#sh mpls forwarding-table
Local Outgoing Prefix Bytes Label Outgoing Next Hop
Label Label or Tunnel Id Switched interface
16 Pop Label 20.20.20.20/32 96772 Et0/0.206 10.10.206.20
17 Pop Label 19.19.19.19/32 0 Et0/0.196 10.10.196.19
18 Pop Label 5.5.5.5/32 9229 Et0/0.56 10.10.56.5
19 16000 2.2.2.2/32 36336 Et0/0.196 10.10.196.19
20 16001 4.4.4.4/32 68130 Et0/0.196 10.10.196.19
I have cleared all process even reloaded all routers but this did not help
After that I decided to configure the next-hop unchanged command on the route reflectors and somehow this fixed the issue for VRF A to make it work for the other VRF’s I needed to redistribute the other PE loopbacks into the core IGP so they would also receive labels. This change also changed the MPLS forwarding table on XR2 in such way that it had a label for R2. I cannot related the next-hop unchanged feature to changing the LDP behavior it only ensures it does not change the next hop to its own address. Below is the BGP configuration of XR2
RP/0/0/CPU0:XR2#sh runn router bgp
Wed May 14 07:36:07.721 UTC
router bgp 2
address-family ipv4 unicast
!
address-family vpnv4 unicast
!
neighbor 2.2.2.2
remote-as 1
ebgp-multihop 255
update-source Loopback1
address-family vpnv4 unicast
route-policy PASS in
route-policy PASS out
!
!
neighbor 5.5.5.5
remote-as 2
update-source Loopback1
address-family vpnv4 unicast
route-policy PASS in
route-reflector-client
route-policy PASS out
!
!
vrf A
rd 100:1
address-family ipv4 unicast
redistribute ospf main
!
!
!
When at the XR2 MPLS forwarding table it is different then the mpls ldp forwarding table. I caanot indetify where the pop label comes from in the mpls forwarding table. The mpls LDP forwarding table and binding table shows the correct label. The router however installes a pop label into the mpls forwarding table.
RP/0/0/CPU0:XR2#sh mpls ldp forwarding
Wed May 14 12:58:52.225 UTC
Codes:
- = GR label recovering, (!) = LFA FRR pure backup path
{} = Label stack with multi-line output for a routing path
G = GR, S = Stale, R = Remote LFA FRR backup
Prefix Label Label(s) Outgoing Next Hop Flags
In Out Interface G S R
--------------- ------- -------------- ------------ ------------------- -----
2.2.2.2/32 16007 19 Gi0/0/0/0.206 10.10.206.6
4.4.4.4/32 16008 20 Gi0/0/0/0.206 10.10.206.6
5.5.5.5/32 16005 18 Gi0/0/0/0.206 10.10.206.6
6.6.6.6/32 16002 ImpNull Gi0/0/0/0.206 10.10.206.6
10.10.56.0/24 16003 ImpNull Gi0/0/0/0.206 10.10.206.6
10.10.196.0/24 16004 ImpNull Gi0/0/0/0.206 10.10.206.6
19.19.19.19/32 16006 17 Gi0/0/0/0.206 10.10.206.6
Can you please help me clear this up.Thanks in advance
Maarten Vervoorn