EVPN-VPWS Interoperability Issue Between XE and XR

[aohanian]

While labbing EVPN-VPWS on CSR1000v and XR9000v, I've found an interoperability issue. I can successfully create an EVPN-VPWS between two CSR1000vs or two XR9000vs, but not between a CSR1000v and XR9000v.

The problem is that XR9000v does not use the control word, and CSR1000v does. I cannot find a way to turn the control word on for the XR9000v, nor can I find a way to turn the control word off on the CSR1000v.

Is there a solution to this that I am overlooking?

Is this also an issue between real hardware, say an ASR920 and ASR9000?

Configs are below:

! CSR1000v

l2vpn evpn instance 1 point-to-point
 vpws context EXAMPLE
  service target 100 source 100
  member Gi3

! XR9000v

l2vpn
 xconnect group EVPN
  p2p EXAMPLE
   interface Gi0/0/0/4
   neighbor evpn evi 1 service 100

Traffic using this VPWS has been captured in the pcap below. The ARP from 10.0.0.1 has the control word set. 10.0.0.1 is behind the CSR1000v. The raw MPLS packets are ARPs from 10.0.0.2, which do not have the control word set. 10.0.0.2 is behind the XR9000v.

https://www.cloudshark.org/captures/a014653cf4d9

You can see the CSR1000v has 8 dropped packets because it cannot decode them since the control word is missing:

#show l2vpn evpn vpws vc all det
EVPN name: EXAMPLE, state: up, type: point-to-point
  EVPN ID: 1
  VPWS Service Instance ID: Source 100, Target 100
  Labels: Local 41, Remote 24006
  Next Hop Address: 10.3.3.3
  Associated member interface Gi3 up, Gi3 status is up
  Dataplane:
    SSM segment/switch IDs: 4141/8193 (used), PWID: 2
  Rx Counters
    0 input transit packets, 0 bytes
    8 drops
  Tx Counters
    5 output transit packets, 610 bytes
    0 drops
  18 VC FSM state transitions, Last 10 shown
    DpUp: Act -> Est, Wed Nov 30 21:51:22.221 (1d05h ago)
    RemDn: Est -> RemWait, Wed Nov 30 22:03:06.127 (1d05h ago)
    EviDn: RemWait -> Prov, Wed Nov 30 22:03:07.588 (1d05h ago)
    EviUp: Prov -> LocWait, Wed Nov 30 22:03:51.747 (1d05h ago)
    LocUp: LocWait -> RemWait, Wed Nov 30 22:03:51.748 (1d05h ago)
    EviDn: RemWait -> Prov, Wed Nov 30 22:05:26.863 (1d05h ago)
    EviUp: Prov -> LocWait, Wed Nov 30 22:06:42.052 (1d05h ago)
    LocUp: LocWait -> RemWait, Wed Nov 30 22:06:42.053 (1d05h ago)
    RemUp: RemWait -> Act, Wed Nov 30 22:08:43.747 (1d05h ago)
    DpUp: Act -> Est, Wed Nov 30 22:08:43.757 (1d05h ago)

[M02@rt37]

Hello @aohanian,

Yes, this issue could arise not only in the simulation environment with CSR1000v and XR9000v, but also in the real network environment with different platforms, such as an ASR920 and an ASR9000.

The use of control word is vendor-specific, and different vendors have different implementations and configurations for EVPN-VPWS.

In your case, it seems that the XR9000v implementation does not support the use of the control word, while the CSR1000v implementation requires it.

To resolve this interoperability issue, you can try this on the CSR1000v side (considering that XR9000v does not use/support the control word):

=> Modify the CSR1000v configuration to not use the control word.

You can do this by disabling the "mpls control-word" option under the interface configuration for the PE-CE link:

[no mpls control-word].

[aohanian]

Thank you, that sounds promising but I'm not seeing that as an option on the PE-CE interface.

R1(config-if)#int gi3
R1(config-if)#no mpls ?
  accounting     Enable MPLS accounting on this interface
  bgp            MPLS BGP commands
  flow           Flow related commands
  ip             Configure dynamic MPLS forwarding for IP
  label          Label properties
  ldp            Configure Label Distribution Protocol (LDP) parameters
  mldp           Configure interface MLDP routing protocol
  mtu            Set MPLS Maximum Transmission Unit
  netflow        Configure Egress Netflow Accounting
  propagate-cos  Copy topmost MPLS Experimental value to exposed IP Prec/MPLS
                 Exp
  tp             Configure MPLS-TP for interface
  traffic-eng    Configure Traffic Engineering parameters
  uni            Enable OIF uni

[M02@rt37]

Hello @aohanian 

And under the l2vpn config, do you have this command ? option under 'l2transport' config.?

This option is only available in the context of L2VPN configuration.

[aohanian]

No I still don't see where I can configure that, can you be more specific?

R1(config-l2vpn)#?
L2VPN configuration commands:
  default     Set a command to its defaults
  exit        Exit from L2VPN configuration mode
  logging     Configure logging flags
  no          Negate a command or set its defaults
  pseudowire  Configure l2vpn pseudowire parameters
  redundancy  Configure L2VPN redundancy parameters
  router-id   Configure a Layer2 router-id
  shutdown    Shutdown Layer2 VPN

R1(config)#l2vpn evpn instance 1 point-to-point
R1(config-evpn-evi)#?
L2VPN EVPN instance configuration commands:
  auto-route-target  Automatically set a route-target
  default            Set a command to its defaults
  exit               Exit from L2VPN evpn instance configuration mode
  no                 Negate a command or set its defaults
  rd                 EVPN Route Distinguisher
  route-target       Route Target VPN Extended Communities
  vpws               EVPN Virtual Private Wire Service configuration

R1(config-evpn-evi)#vpws context TEST
R1(config-evpn-vpws)#?
L2VPN EVPN VPWS configuration commands:
  default   Set a command to its defaults
  exit      Exit from L2VPN evpn vpws configuration mode
  member    EVPN member configuration
  no        Negate a command or set its defaults
  remote    L2VPN remote peer configuration commands
  service   VPWS Service Instance
  shutdown  Shut down the EVPN VPWS service