Routing

Hi guys,

Hope you could help me on this. Some days ago found that a vrf label of a VPLS was mapped to 2 different LSI interfaces each corresponding to a different VRF and actually a different logical system:

1 label mapped to 2 different LSIs:

> show route forwarding-table label 262147
Routing table: default.mpls
MPLS:
Destination Type RtRef Next hop Type Index NhRef Netif
262147 user 0 Pop 2195 2 lsi.1049345

Logical system: MIAV
Routing table: default.mpls
MPLS:
Destination Type RtRef Next hop Type Index NhRef Netif
262147 user 0 Pop 2759 2 lsi.17826311

VPLS 1:

> show vpls connections instance vpls-CUSTOMER-A

Instance: vpls-CUSTOMER-A
Edge protection: Not-Primary
Local site: MIA
connection-site Type St Time last up # Up trans
3 rmt Up Jun 1 18:27:05 2016 1
Remote PE: 10.10.10.31, Negotiated control-word: No
Incoming label: 262147, Outgoing label: 262210
Local interface: lsi.1049345, Status: Up, Encapsulation: VPLS
Description: Intf - vpls vpls-CUSTOMER-A local site 2 remote site 3

VPLS 2 (in logical system):

> show vpls connections instance vpls-CUSTOMER-B logical-system MIAV

Instance: vpls-CUSTOMER-B
VPLS-id: 3793
Neighbor Type St Time last up # Up trans
10.0.120.204(vpls-id 3793) rmt Up Jun 1 18:27:13 2016 1
Remote PE: 10.0.120.204, Negotiated control-word: No
Incoming label: 262147, Outgoing label: 262194
Negotiated PW status TLV: No
Local interface: lsi.17826311, Status: Up, Encapsulation: VLAN
Description: Intf - vpls vpls-CUSTOMER-B neighbor 10.0.120.204 vpls-id 3793
Flow Label Transmit: No, Flow Label Receive: No

I have 2 particular questions here...

1) How is equipment determining to which LSI will traffic be mapped to?

2) Is this normal behavior? Shouldn't be a unique label allocated to a VRF despite it being on default or user logical system? Don't they all share a common forwarding plane?

Thanks in advance.

Hi, 

Each logical system has independent label space, so when a packet arrives at given LS( depending on how you interconnect LSs) it is processed on LS's own context(RIB and FIB) and takes different LSI IFL (which has common parent IFD and should be unique per LS)

HTH,

Krasi

Thanks a lot Krasl! 

D'you know how to associate each LSI with each MPLS table and/or LS? I mean... context ID should be the same for LSI and MPLS table and LS? Or is there any other way to check this?

Thanks!

Hi ,

It is done automatically.

As per your output:

show route forwarding-table label 262147
Routing table: default.mpls
MPLS:
Destination Type RtRef Next hop Type Index NhRef Netif
262147 user 0 Pop 2195 2 lsi.1049345

Logical system: MIAV
Routing table: default.mpls
MPLS:
Destination Type RtRef Next hop Type Index NhRef Netif
262147 user 0 Pop 2759 2 lsi.17826311

When mpls packet(label 262147 )arrives for example into LS "MIAV" ( by means of ingress ifl bound to LS MIAV) then the lookup will be processed in LS MIAV routing context ( i.e. PFE mpls.0 table index corresponding to LS). So the label will be popped and forwarded through lsi.17826311(actually recirculating for L2 lookup)

However if the same packet arrives on ifl bound to "default" LS it will be processed in context of "default" mpls.0 table index into PFE, so it will be popped and forwarded through lsi.1049345

HTH,

Krasi

Thanks once again for clarifying Krasi! For some reason I didn't take into account the inbound interface when analyzing :S

Hello,

This is a ages-old well-known problem with Logical Routers/Systems.

Because each LR/LS has independent Routing Process Daemon a.k.a. RPD, these RPDs run in uncoordinated fashion/are free to pick any label and guess what - with label algorithm being the same, the LR/LS RPDs pick overlapping labels!

Your choices are:

1/ do not use LS for MPLS at all

2/ use "vrf-table-label" only in 1 LS, others can use VT interfaces

3/ host LS uplinks/"core-facing" interfaces on separate FPCs.

HTH

Thx

Alex