Saturday, November 19, 2011

l2tpv3 configuration reference

Reference Comparing , Designing and Deploying VPNs chap - 02 :
L2TPv3 is the enhanced version of L2TPv2 protocol. Mikrotik uses L2TPv2 i suppose but it offer another similar tunneling mechanism as EOIP.
L2TPv3 in cisco provides Pseudo-wire services to the customer. L2TPv3 only require the IP connectivity between peers but it can transport Ethernet, 802.1Q , HDLC, PPP framerelay etc.

Advantage over MPLS is the customer having the full control of their routing domain.

L2TP depolyment methods having 3 topologies

Following Diagram explain simple LAC - LAC L2TPv3 setup.

It uses two types of messages:
control connection messages - used for signaling between LCEs
session data messages - Used to transport layer 2 protocols and connections

Data channel Message Header having Session ID & cookie to correctly associate with the tunnel
Deploying dynamic Pseudowires session
1) configure CEF - Its default in IOSs now.
2) configure a loopback interface to use as the pseduowire endpoint ( need to have the connectivity)
3) configure an L2TP class ( optional)
L2TPv3 Class enables to configure number of control channel configurations.
authentication , keepalive intervals , receive window size, retransmission parameters, timeouts
4) configure a pseudowire class
5) bind attachment circuits to pseudowires

l2tp-class digest_r1
 digest secret 7 096F673A3A2A hash SHA1
pseudowire-class R1toR2
 encapsulation l2tpv3
 sequencing both
 protocol l2tpv3 digest_r1
 ip local interface Loopback0
xconnect peer-address VCID ( should be unique) pw-class [name]
interface FastEthernet1/0
 no ip address
 duplex auto
 speed auto
 xconnect 100 pw-class R1toR2 sequencing both

l2tp-class digest_r2
 digest secret 7 062526126F61 hash SHA1
pseudowire-class R2toR1
 encapsulation l2tpv3
 sequencing both
 protocol l2tpv3 digest_r2
 ip local interface Loopback0
interface FastEthernet1/1
 no ip address
 duplex auto
 speed auto
 xconnect 100 pw-class R2toR1 sequencing both

Between Two Circuits
R6#ping size 1500 repeat 2 df-bit

Type escape sequence to abort.
Sending 2, 1500-byte ICMP Echos to, timeout is 2 seconds:
Packet sent with the DF bit set
Success rate is 100 percent (2/2), round-trip min/avg/max = 72/94/116 ms

CDP from remote devices :
R6#show cdp neighbors detail  | inc Device|IP|Int
Device ID: R1
  IP address:
Interface: FastEthernet1/0,  Port ID (outgoing port): FastEthernet1/0
Device ID: R7
  IP address:
Interface: FastEthernet1/0,  Port ID (outgoing port): FastEthernet1/0

R1#show l2tun session all

L2TP Session Information Total tunnels 1 sessions 1

Session id 56564 is up, tunnel id 23863
  Remote session id is 61449, remote tunnel id 53859
  Remotely initiated session
Call serial number is 10785
Remote tunnel name is R2
  Internet address is
Local tunnel name is R1
  Internet address is
IP protocol 115
  Session is L2TP signaled
  Session state is established, time since change 00:58:25
  DF bit off, ToS reflect disabled, ToS value 0, TTL value 255
  UDP checksums are disabled
  FS cached header information:
    encap size = 28 bytes
    45000014 00000000 FF736353 AC100001
    AC100002 0000F009 00000000
    881 Packets sent, 881 received
    744359 Bytes sent, 744061 received
  Last clearing of counters never
  Counters, ignoring last clear:
    881 Packets sent, 881 received
    744359 Bytes sent, 744061 received
    Receive packets dropped:
      out-of-order:             0
      total:                    0
    Send packets dropped:
      exceeded session MTU:     0
      total:                    0
  Sequencing is on
    Ns 872, Nr 872, 0 out of order packets received
    Packets switched/dropped by secondary path: Tx 0, Rx 0
  Conditional debugging is disabled
  Unique ID is 1
Session Layer 2 circuit, type is Ethernet, name is FastEthernet1/0
  Session vcid is 100
  Circuit state is UP
    Local circuit state is UP
    Remote circuit state is UP

Have to try the interoperability between cisco & mikrotik

1 comment:

Anonymous said...

Do I need to assign a port for the L2 Ethernet ?