L2TPv3 Port-Based Xconnect

Testing port-based xconnect with L2TPv3, it can be seen that both tagged and untagged frames are transported including L2 PDUs for spanning-tree and CDP frames (initially CE1 was connected to PE1 and CE2 to PE2).

! CE1
interface FastEthernet0/0
 description Link to PE1
 ip address 192.168.0.1 255.255.255.252

interface FastEthernet0/0.10
 encapsulation dot1Q 10
 ip address 192.168.10.1 255.255.255.252

interface FastEthernet0/0.20
 encapsulation dot1Q 20
 ip address 192.168.20.1 255.255.255.252


! PE1
pseudowire-class L2TPv3
 encapsulation l2tpv3
 ip local interface FastEthernet0/1

interface FastEthernet0/0
 description Link to CE1
 no ip address
 xconnect 192.0.2.2 123 pw-class L2TPv3

interface FastEthernet0/1
 description Link to PE2
 ip address 192.0.2.1 255.255.255.252


! PE2
pseudowire-class L2TPv3
 encapsulation l2tpv3
 ip local interface FastEthernet0/1

interface FastEthernet0/0
 description Link to CE2
 no ip address
 xconnect 192.0.2.1 123 pw-class L2TPv3

interface FastEthernet0/1
 description Link to PE1
 ip address 192.0.2.2 255.255.255.252


! CE2
interface FastEthernet0/0
 description Link to PE2
 ip address 192.168.0.2 255.255.255.252

interface FastEthernet0/0.10
 encapsulation dot1Q 10
 ip address 192.168.10.2 255.255.255.252

interface FastEthernet0/0.20
 encapsulation dot1Q 20
 ip address 192.168.20.2 255.255.255.252


CE1#ping 192.168.0.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 192.168.0.2, timeout is 2 seconds:
.!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 36/48/64 ms


CE1#ping 192.168.10.2 repeat 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 192.168.10.2, timeout is 2 seconds:
.
Success rate is 0 percent (0/1)

CE1#ping 192.168.10.2 repeat 1
Type escape sequence to abort.
Sending 1, 100-byte ICMP Echos to 192.168.10.2, timeout is 2 seconds:
!

Pringing from CE1 to CE2 in a dot1q tagged sub-interface on VLAN 10. These are the raw packet captures from wireshark as it doesn't display the packet properly in the GUI:

! CE1 original ping request to CE2 (192.168.10.1->192.168.10.2) transmitted to PE1
ca 04 15 a4 00 08 ca 03 17 d0 00 08 81 00 00 14
08 00 45 00 00 64 00 0e 00 00 ff 01 12 37 c0 a8
14 01 c0 a8 14 02 08 00 c7 e6 00 0a 00 00 00 00
00 00 00 09 b6 50 ab cd ab cd ab cd ab cd ab cd
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd
ab cd ab cd ab cd

! PE1 L2TP encapsulated ping request frame being sent to PE2
ca 02 03 d0 00 06 ca 01 11 10 00 06 08 00 45 00
00 8e 00 37 00 00 fe 73 37 c2 c0 00 02 01 c0 00
02 02 7e 1e e4 22 ca 04 15 a4 00 08 ca 03 17 d0
00 08 81 00 00 14 08 00 45 00 00 64 00 0d 00 00
ff 01 12 38 c0 a8 14 01 c0 a8 14 02 08 00 57 19
00 09 00 00 00 00 00 00 00 08 27 20 ab cd ab cd  
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd 
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd  
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd 
ab cd ab cd ab cd ab cd ab cd ab cd

! The first part is the PE1 overhead
ca 02 03 d0 00 06 ca 01 11 10 00 06 08 00 45 00
00 8e 00 37 00 00 fe 73 37 c2 c0 00 02 01 c0 00
02 02 7e 1e e4 22

! The second part is the original ping request receives from CE1
ca 04 15 a4 00 08 ca 03 17 d0
00 08 81 00 00 14 08 00 45 00 00 64 00 0d 00 00
ff 01 12 38 c0 a8 14 01 c0 a8 14 02 08 00 57 19
00 09 00 00 00 00 00 00 00 08 27 20 ab cd ab cd  
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd 
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd  
ab cd ab cd ab cd ab cd ab cd ab cd ab cd ab cd 
ab cd ab cd ab cd ab cd ab cd ab cd

Now with SW1 connected to PE1 and SW2 connected to PE2 we can see that L2CPs are forwarded over the port based pseudowire:

SW1#show spanning-tree vlan 10

 VLAN10 is executing the ieee compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address cc05.1328.0001
  Configured hello time 1, max age 6, forward delay 4
  We are the root of the spanning tree
  Topology change flag not set, detected flag not set
  Number of topology changes 1 last change occurred 00:08:57 ago
          from FastEthernet1/0
  Times:  hold 1, topology change 10, notification 1
          hello 1, max age 6, forward delay 4
  Timers: hello 0, topology change 0, notification 0, aging 300

 Port 41 (FastEthernet1/0) of VLAN10 is forwarding
   Port path cost 19, Port priority 128, Port Identifier 128.41.
   Designated root has priority 32768, address cc05.1328.0001
   Designated bridge has priority 32768, address cc05.1328.0001
   Designated port id is 128.41, designated path cost 0
   Timers: message age 0, forward delay 0, hold 0
   Number of transitions to forwarding state: 1
   BPDU: sent 545, received 0


SW2#show spanning-tree vlan 10

 VLAN10 is executing the ieee compatible Spanning Tree protocol
  Bridge Identifier has priority 32768, address cc06.17ec.0001
  Configured hello time 1, max age 6, forward delay 4
  Current root has priority 32768, address cc05.1328.0001
  Root port is 41 (FastEthernet1/0), cost of root path is 19
  Topology change flag not set, detected flag not set
  Number of topology changes 0 last change occurred 00:00:42 ago
  Times:  hold 1, topology change 10, notification 1
          hello 1, max age 6, forward delay 4
  Timers: hello 0, topology change 0, notification 0, aging 300

 Port 41 (FastEthernet1/0) of VLAN10 is forwarding
   Port path cost 19, Port priority 128, Port Identifier 128.41.
   Designated root has priority 32768, address cc05.1328.0001
   Designated bridge has priority 32768, address cc05.1328.0001
   Designated port id is 128.41, designated path cost 0
   Timers: message age 1, forward delay 0, hold 0
   Number of transitions to forwarding state: 1
   BPDU: sent 0, received 42


SW2#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
                  S - Switch, H - Host, I - IGMP, r - Repeater

Device ID        Local Intrfce     Holdtme    Capability  Platform  Port ID
PE2              Fas 1/0            158           R       7206VXR   Fas 0/0
SW1              Fas 1/0            154         R S I     3660      Fas 1/0

The below packet captures show the VLAN 10 BPDUS

! SW1 original ST BPDU sent to SW2, transmitted to PE1
01 00 0c cc cc cd cc 05 13 28 f1 00 81 00 00 0a
00 32 aa aa 03 00 00 0c 01 0b 00 00 00 00 00 80
00 cc 05 13 28 00 01 00 00 00 00 80 00 cc 05 13
28 00 01 80 29 00 00 06 00 01 00 04 00 00 00 00
00 02 00 0a

! PE1 L2TP encapsulated BPDU transmitted to PE2
ca 02 03 d0 00 06 ca 01 11 10 00 06 08 00 45 00
00 5c 07 1f 00 00 fe 73 31 0c c0 00 02 01 c0 00
02 02 32 f8 c9 5d 01 00 0c cc cc cd cc 05 13 28
f1 00 81 00 00 0a 00 32 aa aa 03 00 00 0c 01 0b
00 00 00 00 00 80 00 cc 05 13 28 00 01 00 00 00
00 80 00 cc 05 13 28 00 01 80 29 00 00 06 00 01
00 04 00 00 00 00 00 02 00 0a

Output from PE1 showing L2TPv3 xconnect/tunnel info

PE1#show xconnect all 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   Fa0/0(Ethernet)              UP l2tp 192.0.2.2:123                UP
            Interworking: none                   Session ID: 3255406499
                                                 Tunnel ID: 1083768332
                                                 Protocol State: UP
                                                 Remote Circuit State: UP
                                                 pw-class: L2TPv3

PE1#show l2tp

L2TP Tunnel and Session Information Total tunnels 1 sessions 1

LocTunID   RemTunID   Remote Name   State  Remote Address  Sessn L2TP Class/
                                                           Count VPDN Group
1083768332 1688674825 PE2           est    192.0.2.2       1     l2tp_default_cl

LocID      RemID      TunID      Username, Intf/      State  Last Chg Uniq ID
                                 Vcid, Circuit
3255406499 855165277  1083768332 123, Fa0/0           est    00:33:03 1


PE1#show l2tp tunnel all id 1083768332

L2TP Tunnel Information Total tunnels 1 sessions 1

Tunnel id 1083768332 is up, remote id is 1688674825, 1 active sessions
  Locally initiated tunnel
  Tunnel state is established, time since change 00:33:33
  Tunnel transport is IP  (115)
  Remote tunnel name is PE2
    Internet Address 192.0.2.2, port 0
  Local tunnel name is PE1
    Internet Address 192.0.2.1, port 0
  L2TP class for tunnel is l2tp_default_class
  Counters, taking last clear into account:
    6101 packets sent, 94 received
    412051 bytes sent, 16564 received
    Last clearing of counters never
  Counters, ignoring last clear:
    6101 packets sent, 94 received
    412051 bytes sent, 16564 received
  Control Ns 9, Nr 32
  Local RWS 1024 (default), Remote RWS 1024
  Control channel Congestion Control is disabled
  Tunnel PMTU checking disabled
  Retransmission time 1, max 1 seconds
  Unsent queuesize 0, max 0
  Resend queuesize 0, max 2
  Total resends 0, ZLB ACKs sent 31
  Total out-of-order dropped pkts 0
  Total out-of-order reorder pkts 0
  Total peer authentication failures 0
  Current no session pak queue check 0 of 5
  Retransmit time distribution: 0 0 0 0 0 0 0 0 0
  Control message authentication is disabled


PE1#show l2tp counters tunnel id 1083768332
L2TP tunnel control message statistics:
Tunnel LocID: 1083768332  RemID: 1688674825
Local Address: 192.0.2.1
Remote Address: 192.0.2.2

                   XMIT      RE-XMIT         RCVD         DROP
             ==========   ==========   ==========   ==========
ZLB                  33            0            7            0
SCCRQ                 1            0            0            0
SCCRP                 0            0            1            0
SCCCN                 1            0            0            0
StopCCN               0            0            0            0
Hello                 4            0           31            0
OCRQ                  0            0            0            0
OCRP                  0            0            0            0
OCCN                  0            0            0            0
ICRQ                  1            0            0            0
ICRP                  0            0            1            0
ICCN                  1            0            0            0
CDN                   0            0            0            0
WEN                   0            0            0            0
SLI                   1            0            1            0
EXP ACK               0            0            0            0
SRRQ                  0            0            0            0
SRRP                  0            0            0            0
CiscoACK              0            0            0            0
Total                42            0           41            0

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