Hi all,
I'm studying for CCIE service provider with the INE all access pass. After
watching the video about:"Inter AS MPLS L3VPN Option C - ASBRs Peering
BGP+Label " 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 VRFbs 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 VRFbs 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
XR2 has no labels within BGP for ipv4 only for vpnv4. It the option C
example in the stage where R2 and XR2 still does not have the next-hop
unchange feature enabled and the traffic should flow via XR2 and R2 BGP
labels are only exchange between XR1 and R1. XR1 is redistributing the
routes into the IGP (OSPF in this case) because it is the IGP LDP should
generate the labels so XR2 should have the label from LDP and it has only
it does not install them.
Also the strange thing if I also distribute R4bs loopback with the same
technology it does have a label from LDP only R2 show strange behavior
which I cannot clarify.
RP/0/0/CPU0:XR2#sh mpls forwarding
Thu May 15 09:56:26.496 UTC
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
----- ----------- ------------------ ------------ ---------------
------------
16001 Unlabelled 8.8.8.8/32[V] Gi0/0/0/0.208 10.10.208.8 7440
16002 Pop 6.6.6.6/32 Gi0/0/0/0.206 10.10.206.6 146640
16003 17 19.19.19.19/32 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 Pop 2.2.2.2/32 Gi0/0/0/0.206 10.10.206.6 133952
16006 Pop 10.10.56.0/24 Gi0/0/0/0.206 10.10.206.6 0
16007 19 5.5.5.5/32 Gi0/0/0/0.206 10.10.206.6 180691
*16008 18 4.4.4.4/32 <http://4.4.4.4/32> Gi0/0/0/0.206
10.10.206.6 0*
16009 Aggregate A: Per-VRF Aggr[V] A 0
16010 22 100:2:10.10.115.0/24 \
5.5.5.5 0
16011 23 100:2:11.11.11.11/32 \
5.5.5.5 0
16012 24 100:3:10.10.125.0/24 \
5.5.5.5 0
16013 25 100:3:12.12.12.12/32 \
5.5.5.5 52220
16014 25 10.10.10.10/32[V] 2.2.2.2 7280
16015 26 10.10.104.0/24[V] 2.2.2.2 0
Can you please help me clear this up.Thanks in advance
Maarten Vervoorn
Blogs and organic groups at http://www.ccie.net
Received on Wed Jun 04 2014 - 21:52:52 ART
This archive was generated by hypermail 2.2.0 : Tue Jul 01 2014 - 06:32:35 ART