MTU L2VPN VFI BETWEEN ASR902 vs ASR9000

[IEC1233788]

Hi community,

I need your help to the next case, I try to establish a Pseudowire between an ASR902 and ASR9000.

In the ASR we configure the MTU in bridge-domian to 9216, but in ASR902 the maximum MTU in the VFI is 9180. The Pseudowire is DOWN for  the MTU mistmatch

I know that we can change the MTU in ASR9000 to 9180 to the Pseudowire work, but my question is in reference about the maximum MTU supported in ASR902, this because in the ASR9000 we have a lot pseudowires into the this bridge-domain to others ASR9k and ME3600x, ME3800x.

Configuration in ASR9002, the MTU is set to 9180

ASR902_PE_SITE_B#show mpls l2transport vc 2829 detail |  inc erro|MTU
    Last error: Pseudowire MTU mismatch with peer
    MTU: local 9180, remote 9216
    transit packet drops:  receive 0, seq error 0, send 0
ASR902_PE_SITE_B#

ASR902_PE_SITE_B(config)#l2vpn vfi context TEST_L2VPN
ASR902_PE_SITE_B(config-vfi)#mt
ASR902_PE_SITE_B(config-vfi)#mtu ?
  <1500-9180>  Maximum Transmission Unit value
  <cr>

Configuration in ASR9000, the MTU is set to 9216

RP/0/RSP0/CPU0:PE-ME-SITE_A#

 bridge group TEST_L2VPN
  bridge-domain CULIA_MAZA
   mtu 9216
   interface GigabitEthernet0/1/0/0.2829
   !
   vfi CULIA_MAZA
    vpn-id 28290
    !
    neighbor 192.168.74.X pw-id 2829

RP/0/RSP0/CPU0:PE-ME-SITE_A#show l2vpn  bridge-domain  neighbor 192.168.74.83  pw-id 2829  detail |  inc "MTU|Err|type"
Fri Aug  5 17:04:32.385 CDT
  Bridge MTU: 9216
        PW type Ethernet, control word disabled, interworking none
          MTU          9216                           9180                         
          PW type      Ethernet                       Ethernet                     
          VCCV CV type 0x2                            0x2                          
          VCCV CC type 0x6                            0x2                          
        Error: MTU mismatched
RP/0/RSP0/CPU0:PE-ME-SITE_A#

I really apreciate your help.

Regards.

[xthuijs · Accepted solution]

the mtu for the PW is merely a signaling thing and doesnt affect any fragmentation or forwarding.

the mtu can also be taken from the attachment circuit.

the maximum mtu for the asr902 is also 9216.

cheers!

xander

[IEC1233788]

Hi Xander,

Thanks for your support, I changed VFI to Xconnect and now the MTU is taken for the physical interface to 9216.

l2vpn xconnect context CLIENT
 member GigabitEthernet0/1/1 service-instance 1234
 member 1.1.1.1 1234 encapsulation mpls

I see the diference in the new format to configure L2VPN in ASR900 where we don't configure a SVI whit xconnect. In this case the MTU is taken for the SVI.

Is it possible configure a pseudowire in "Vlan-Mode" in ASR900?

PW VC Type 5 port mode

PW VC type 4 VLAN mode

Regards.

[xthuijs · Accepted solution]

for the asr9000 it is a bit more straight forward, in the l2vpn configuration youhave direct control in the pw class what type of transport you want to use.

for the asr900 the config mode(l) defines a vc type 4 or 5.

http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_l2_vpns/configuration/xe-3s/mp-l2-vpns-xe-3s-book/mp-any-transport-xe.html#GUID-FB013E0C-B37F-48CF-B2B0-374A45B9B9EC

it generally doesnt really matter what way you go about, 4 or 5. Unless you have very strict qos (propagation) requirements and separation between exp and dot1p. If you dont care about that, either one is fine.

cheers!

xander