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L2TPv3 and Spanning-tree issue

 

Question:

We have a need to extend additional Vlans (separate broadcast segments) to a remote site; which using L2TPv3 works very well. However, we are having problems understanding why we cannot get Cisco spanning-tree MST 802.1s operational across the L2TPv3 topology. The switch command sh span mst reveals both SW1 and SW2 claim ROOT status.  Does anyone know for sure if MST over L2TPv3 does work and perhaps knows how to get it operational --OR-- MST over L2TPv3 does not work?  Also, is L2TPv3 an obsolete legacy technology and has been replaced by something more functional?

 

Topology in use: (see attached MS Paint topology; I couldn't get the pic to appears here)

 

 

 

 

 

 

 

 

What we know:

When using the routers physical interfaces (G0/0) to extend a single Vlan; spanning-tree MST 802.1s operates as expected eg. SW1 becomes the root as configured and SW2 is backup root.

When using the routers sub-interfaces (G0/0.1, G0/0.2 etc.) to extend multiple Vlans; spanning-tree MST 802.1s does  NOT operate as configured. Eg. Both SW1 and SW2 claim root status

Placing a hub between SW1 and L2tun-1; Wireshark shows spanning-tree MST, cdp, vtp etc. is being sent out SW1 F1/0/16 interface. Spanning-tree MST frames have the user configured name, revision # and Vlan instance parameters. I can post this output if someone thinks it will be useful in resolving this issue.

 

SW1# sh int trunk

Port        Mode             Encapsulation  Status        Native vlan

Fa1/0/16    on               802.1q         trunking      1

Port        Vlans allowed on trunk

Fa1/0/16    1-4094

Port        Vlans allowed and active in management domain

Fa1/0/16    1-3

Port        Vlans in spanning tree forwarding state and not pruned

Fa1/0/16    1-3

 

 

SW2# sh int trunk        

Port        Mode             Encapsulation  Status        Native vlan

Fa1/0/13    on               802.1q         trunking      1

Port        Vlans allowed on trunk

Fa1/0/13    1-4094

Port        Vlans allowed and active in management domain

Fa1/0/13    1-3

Port        Vlans in spanning tree forwarding state and not pruned

Fa1/0/13    1-3

 

 

SW1# sh cdp nei

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID

L2Tun-1          Fas 1/0/16        127             R S I  2821      Gig 0/0.1

SW2              Fas 1/0/16        151             R S I  WS-C3750- Fas 1/0/13

 

 

 

SW2# sh cdp nei

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID

L2Tun-2          Fas 1/0/13        155             R S I  2821      Gig 0/0.1

SW1              Fas 1/0/13        136             R S I  WS-C3750- Fas 1/0/16

 

 

SW1# sh arp

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.0.0.1                -   0013.8072.1a40  ARPA   Vlan1

Internet  10.0.0.2                2   000f.2325.a740  ARPA   Vlan1

Internet  192.168.2.1             -   0013.8072.1a46  ARPA   Vlan2

Internet  192.168.2.2            12   000f.2325.a748  ARPA   Vlan2

Internet  192.168.3.1             -   0013.8072.1a47  ARPA   Vlan3

Internet  192.168.3.2            12   000f.2325.a749  ARPA   Vlan3

 

 

SW2# sh arp

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.0.0.1                2   0013.8072.1a40  ARPA   Vlan1

Internet  10.0.0.2                -   000f.2325.a740  ARPA   Vlan1

Internet  192.168.2.1            12   0013.8072.1a46  ARPA   Vlan2

Internet  192.168.2.2             -   000f.2325.a748  ARPA   Vlan2

Internet  192.168.3.1            12   0013.8072.1a47  ARPA   Vlan3

Internet  192.168.3.2             -   000f.2325.a749  ARPA   Vlan3

 

 

SW1# sh span mst   

 

##### MST0    vlans mapped:   1-800

Bridge        address 0013.8072.1a00  priority      4096  (4096 sysid 0)

Root          this switch for the CIST

Operational   hello time 2 , forward delay 15, max age 20, txholdcount 6

Configured    hello time 2 , forward delay 15, max age 20, max hops    20

 

Interface        Role Sts Cost      Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa1/0/8          Desg FWD 200000    128.10   P2p

Fa1/0/10         Desg FWD 200000    128.12   P2p

Fa1/0/16         Desg FWD 200000    128.18   P2p

 

 

SW2# sh span mst   

 

##### MST0    vlans mapped:   1-800

Bridge        address 000f.2325.a700  priority      61440 (61440 sysid 0)

Root          this switch for the CIST

Operational   hello time 2 , forward delay 15, max age 20, txholdcount 6

Configured    hello time 2 , forward delay 15, max age 20, max hops    20

 

Interface        Role Sts Cost      Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa1/0/2          Desg FWD 200000    128.4    P2p

Fa1/0/13         Desg FWD 200000    128.15   P2p

 

 

SW1# sh ip int br | e do

Interface              IP-Address      OK? Method Status                Protocol

Vlan1                  10.0.0.1        YES manual up                    up     

Vlan2                  192.168.2.1     YES manual up                    up     

Vlan3                  192.168.3.1     YES manual up                    up     

FastEthernet1/0/8      unassigned      YES unset  up                    up     

FastEthernet1/0/10     unassigned      YES unset  up                    up     

FastEthernet1/0/16     unassigned      YES unset  up                    up

 

SW2# sh ip int br | e do

Interface              IP-Address      OK? Method Status                Protocol

Vlan1                  10.0.0.2        YES manual up                    up     

Vlan2                  192.168.2.2     YES manual up                    up     

Vlan3                  192.168.3.2     YES manual up                    up     

FastEthernet1/0/2      unassigned      YES unset  up                    up     

FastEthernet1/0/13     unassigned      YES unset  up                    up   

 

 

SW1#ping 10.0.0.2

Sending 5, 100-byte ICMP Echos to 10.0.0.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/9 ms

SW1#ping 192.168.2.2

Sending 5, 100-byte ICMP Echos to 192.168.2.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/5/9 ms

SW1#ping 192.168.3.2

Sending 5, 100-byte ICMP Echos to 192.168.3.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/2/8 ms

 

 

SW2#ping 10.0.0.1

Sending 5, 100-byte ICMP Echos to 10.0.0.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/5/9 ms

SW2#ping 192.168.2.1

Sending 5, 100-byte ICMP Echos to 192.168.2.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/4/9 ms

SW2#ping 192.168.3.1

Sending 5, 100-byte ICMP Echos to 192.168.3.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 1/3/8 ms

 

 

L2Tun-1# sh xcon all

Legend:    XC ST=Xconnect State  S1=Segment1 State  S2=Segment2 State

  UP=Up       DN=Down            AD=Admin Down      IA=Inactive

  SB=Standby  RV=Recovering      NH=No Hardware

 

XC ST  Segment 1                         S1 Segment 2                         S2

------+---------------------------------+--+---------------------------------+--

UP     ac   Gi0/0.1:1(Eth VLAN)          UP l2tp 10.2.0.2:1                   UP

UP     ac   Gi0/0.2:2(Eth VLAN)          UP l2tp 10.2.0.2:2                   UP

UP     ac   Gi0/0.3:3(Eth VLAN)          UP l2tp 10.2.0.2:3                   UP

 

 

L2Tun-2# sh xcon all

Legend:    XC ST=Xconnect State  S1=Segment1 State  S2=Segment2 State

  UP=Up       DN=Down            AD=Admin Down      IA=Inactive

  SB=Standby  RV=Recovering      NH=No Hardware

 

XC ST  Segment 1                         S1 Segment 2                         S2

------+---------------------------------+--+---------------------------------+--

UP     ac   Gi0/0.1:1(Eth VLAN)          UP l2tp 10.1.0.1:1                   UP

UP     ac   Gi0/0.2:2(Eth VLAN)          UP l2tp 10.1.0.1:2                   UP

UP     ac   Gi0/0.3:3(Eth VLAN)          UP l2tp 10.1.0.1:3                   UP

 

 

L2Tun-1# sh xconnect interface g0/0.1 det

Legend:    XC ST=Xconnect State  S1=Segment1 State  S2=Segment2 State

  UP=Up       DN=Down            AD=Admin Down      IA=Inactive

  SB=Standby  RV=Recovering      NH=No Hardware

 

XC ST  Segment 1                         S1 Segment 2                         S2

------+---------------------------------+--+---------------------------------+--

UP     ac   Gi0/0.1:1(Eth VLAN)          UP l2tp 10.2.0.2:1                   UP

            Interworking: none                   Session ID: 4114808408        

                                                 Tunnel ID: 3813445228         

                                                 Protocol State: UP            

                                                 Remote Circuit State: UP      

                                                 pw-class: NATIVE   

 

 

L2Tun-2# sh xconnect interface g0/0.1 detail

Legend:    XC ST=Xconnect State  S1=Segment1 State  S2=Segment2 State

  UP=Up       DN=Down            AD=Admin Down      IA=Inactive

  SB=Standby  RV=Recovering      NH=No Hardware

 

XC ST  Segment 1                         S1 Segment 2                         S2

------+---------------------------------+--+---------------------------------+--

UP     ac   Gi0/0.1:1(Eth VLAN)          UP l2tp 10.1.0.1:1                   UP

            Interworking: none                   Session ID: 2454835785        

                                                 Tunnel ID: 2658829555         

                                                 Protocol State: UP            

                                                 Remote Circuit State: UP      

                                                 pw-class: NATIVE

 

 

hostname L2Tun-1

!

boot-start-marker

boot system flash:c2800nm-adventerprisek9-mz.151-4.M8.bin

boot-end-marker

!

no ip source-route

ip cef

no ip domain lookup

no ipv6 cef

!

l2tp-class MGT

 authentication

 hello 5

 password 7 062B2815

 cookie size 8

!

vtp domain R19

vtp mode transparent

!

pseudowire-class NATIVE

 encapsulation l2tpv3

 protocol l2tpv3 MGT

 ip local interface Loopback1

 ip pmtu

!

interface Loopback1

 ip address 10.1.0.1 255.255.255.255

!

interface GigabitEthernet0/0

 mtu 1600

 no ip address

!

interface GigabitEthernet0/0.1

 encapsulation dot1Q 1 native

 xconnect 10.2.0.2 1 pw-class NATIVE

!

interface GigabitEthernet0/0.2

 encapsulation dot1Q 2

 xconnect 10.2.0.2 2 pw-class NATIVE

!

interface GigabitEthernet0/0.3

 encapsulation dot1Q 3

 xconnect 10.2.0.2 3 pw-class NATIVE

!        

interface GigabitEthernet0/1

 mtu 1600

 ip address 10.0.0.130 255.255.255.128

!

router ospf 1

 router-id 10.0.0.130

 network 10.0.0.0 0.255.255.255 area 0

 network 192.168.0.0 0.0.0.255 area 0

 network 192.192.192.1 0.0.0.0 area 0

 

 

hostname L2Tun-2

!

boot-start-marker

boot system flash:c2800nm-adventerprisek9-mz.151-4.M8.bin

boot-end-marker

!

no ip source-route

ip cef

no ip domain lookup

no ipv6 cef

!

l2tp-class MGT

 authentication

 hello 5

 password 7 07220678

 cookie size 8

!

vtp domain R18

vtp mode transparent

!

pseudowire-class NATIVE

 encapsulation l2tpv3

 protocol l2tpv3 MGT

 ip local interface Loopback1

 ip pmtu

!

interface Loopback1

 ip address 10.2.0.2 255.255.255.255

!

interface GigabitEthernet0/0

 mtu 1600

 no ip address

!

interface GigabitEthernet0/0.1

 encapsulation dot1Q 1 native

 xconnect 10.1.0.1 1 pw-class NATIVE

!

interface GigabitEthernet0/0.2

 encapsulation dot1Q 2

 xconnect 10.1.0.1 2 pw-class NATIVE

!

interface GigabitEthernet0/0.3

 encapsulation dot1Q 3

 xconnect 10.1.0.1 3 pw-class NATIVE

!

interface GigabitEthernet0/1

 mtu 1600

 ip address 10.0.0.129 255.255.255.128

!

router ospf 1

 router-id 10.0.0.129

 network 10.0.0.0 0.255.255.255 area 0

 network 192.168.0.0 0.0.0.255 area 0

Everyone's tags (1)
1 REPLY
Bronze

Hey Jimmy,Sorry for the slow

Hey Jimmy,

Sorry for the slow response but it took me a while to lab it up.

1st problem I see is you have duplicate IP addresses assigned, Vlan1 is using 10 space as-well-as your PE to cloud links. I guess since your frames are encapsulated on the PE links in L2TPv3 encapsulation this should not be an issue but it was a problem using your posted configurations in my lab setup.

Also, since all frames that egress SW1 (to PE) are tagged (each with its own Vlan ID) this is why all the protocols are functional except STP. Putting Wireshark on the wire, this is what the spanning-tree frames looks like, Notice no VLAN ID.

Frame 1: 135 bytes on wire (1080 bits), 135 bytes captured (1080 bits)
    Encapsulation type: Ethernet (1)
    Arrival Time: Jul 22, 2014 14:16:25.211808000 Eastern Daylight Time
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1406052985.211808000 seconds
    [Time delta from previous captured frame: 0.000000000 seconds]
    [Time delta from previous displayed frame: 0.000000000 seconds]
    [Time since reference or first frame: 0.000000000 seconds]
    Frame Number: 1
    Frame Length: 135 bytes (1080 bits)
    Capture Length: 135 bytes (1080 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:llc:stp]
    [Coloring Rule Name: Broadcast]
    [Coloring Rule String: eth[0] & 1]
IEEE 802.3 Ethernet
    Destination: Spanning-tree-(for-bridges)_00 (01:80:c2:00:00:00)
        Address: Spanning-tree-(for-bridges)_00 (01:80:c2:00:00:00)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
    Source: Cisco_72:1a:12 (00:13:80:72:1a:12)
        Address: Cisco_72:1a:12 (00:13:80:72:1a:12)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Length: 121
Logical-Link Control
    DSAP: Spanning Tree BPDU (0x42)
    IG Bit: Individual
    SSAP: Spanning Tree BPDU (0x42)
    CR Bit: Command
    Control field: U, func=UI (0x03)
        000. 00.. = Command: Unnumbered Information (0x00)
        .... ..11 = Frame type: Unnumbered frame (0x03)
Spanning Tree Protocol
    Protocol Identifier: Spanning Tree Protocol (0x0000)
    Protocol Version Identifier: Multiple Spanning Tree (3)
    BPDU Type: Rapid/Multiple Spanning Tree (0x02)
    BPDU flags: 0x7c (Agreement, Forwarding, Learning, Port Role: Designated)
        0... .... = Topology Change Acknowledgment: No
        .1.. .... = Agreement: Yes
        ..1. .... = Forwarding: Yes
        ...1 .... = Learning: Yes
        .... 11.. = Port Role: Designated (3)
        .... ..0. = Proposal: No
        .... ...0 = Topology Change: No
    Root Identifier: 32768 / 0 / 00:13:80:72:1a:00
        Root Bridge Priority: 32768
        Root Bridge System ID Extension: 0
        Root Bridge System ID: Cisco_72:1a:00 (00:13:80:72:1a:00)
    Root Path Cost: 0
    Bridge Identifier: 32768 / 0 / 00:13:80:72:1a:00
        Bridge Priority: 32768
        Bridge System ID Extension: 0
        Bridge System ID: Cisco_72:1a:00 (00:13:80:72:1a:00)
    Port identifier: 0x8012
    Message Age: 0
    Max Age: 20
    Hello Time: 2
    Forward Delay: 15
    Version 1 Length: 0
    Version 3 Length: 80
    MST Extension
        MST Config ID format selector: 0
        MST Config name: REGION1
        MST Config revision: 3
        MST Config digest: e13a80f11ed0856acd4ee3476941c73b
        CIST Internal Root Path Cost: 0
        CIST Bridge Identifier: 32768 / 0 / 00:13:80:72:1a:00
            CIST Bridge Priority: 32768
            CIST Bridge Identifier System ID Extension: 0
            CIST Bridge Identifier System ID: Cisco_72:1a:00 (00:13:80:72:1a:00)
        CIST Remaining hops: 20
        MSTID 1, Regional Root Identifier 24576 / 00:13:80:72:1a:00
            MSTI flags: 0x7c (Agreement, Forwarding, Learning, Port Role: Designated)
                0... .... = Topology Change Acknowledgment: No
                .1.. .... = Agreement: Yes
                ..1. .... = Forwarding: Yes
                ...1 .... = Learning: Yes
                .... 11.. = Port Role: Designated (3)
                .... ..0. = Proposal: No
                .... ...0 = Topology Change: No
            MSTID 1, priority 24576 Root Identifier 00:13:80:72:1a:00
            Internal root path cost: 0
            Bridge Identifier Priority: 6
            Port identifier priority: 8
            Remaining hops: 20
 
Now, as far as getting STP frames to the other side, check out this doc!!!

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3550/software/release/12-1_13_ea1/configuration/guide/3550scg/swtunnel.html

Hope this works for you

Frank

 
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