MPLS L2VPNs

L2VPNs offer a means to tunnel layer 2 traffic over MPLS network. The L2VPNs can be point to point or point to multipoint. Let’s take a look on what options are available to us

Point to point L2VPNs

The point to point L2VPNS are technically referred to as Virtual Private Wire Service (VPWS). VPWS has a lot of other names. In Nokia (Alcatel-Lucent) SR OS they are called “x”pipe, where “x” represent type of traffic being transported, like epipe – Ethernet VPWS, cpipe – CESoPSN VPWS and etc. Cisco world has another marvelous name AToM, which stands for Any Transport over MPLS. There are also a lot of other abbreviations like PW (PseudoWire), PWE3 (PseudoWire End-to-End Emulation), VLL (virtual Leased Line) and so on. VPWS can be categorized in three types:

• Martini L2VPN
• VPWS Kompella using BGP auto-discovery and signalling
• VPWS BGP Auto discovery and LDP signalling FEC129;

1. Martini L2VPNs

This type of VPWS uses LDP as its signalling protocol. They are mostly referred to as layer 2 circuit or cross-connect. This implementation does not offer auto discovery features and both ends of the connections have to be configured manually to establish targeted LDP sessions. There is another implementation of this that uses IP instead of MPLS to tunnel layer 2 traffic called L2TPv3 in Cisco.

2. VPWS Kompella using BGP auto-discovery and signalling

This type of VPWS uses BGP instead of LDP, the neighbours participating in a layer 2 connection can be discovered automatically and sessions will be established using BGP as a signalling protocol. BGP is used as both neighbor discovery protocol and signalling protocol. To accommodate these features a new BGP NLRI was introduced to the NLRI is l2vpn. This design uses the concept of site-ids to establish sessions, the site ids are supposed to be on contagious blocks also uses extended BGP communities to carry neighbour and layer 2 route information such as route-target, route-distinguisher, site-id and remote-site-id.

Note: Cisco does not support this implementation

3. VPWS BGP Auto discovery and LDP signalling FEC129;

Very much like the previous design, this type of VPWS uses BGP for neighbour discovery only then LDP is used for signalling. This implementation uses BGP NLRI l2vpn for auto-discovery-only as well as extended BGP communities; route targets and l2vpn-id. The presence of the l2vpn-id designates that FEC 129 LDP signaling is used for the routing instance. The absence of l2vpn-id indicates that BGP signaling is used instead

Point to multipoint L2VPNs

The point to point L2VPNS are technically referred to as Virtual Private Line Service (VPLS) in this type of configuration the provider networks acts as a switch and the PEs involved will be learning mac-address information.

1. VPLS Manual discovery and LDP signalling FEC128

This implementation requires neighbouring routers participating in the VPLS instance to be explicitly configured on each of the participating routers and it uses LDP as the signalling protocol.

2. VPLS BGP Auto discovery and LDP signalling FEC129

This is an enhancement to the above implementation that offers auto discovery of neighbors participating in a VPLS instance. Uses the BGP NLRI l2vpn for auto-discovery-only as well as extended BGP communities; route targets and l2vpn-id. FEC 129 uses BGP autodiscovery to convey endpoint information, so you do not need to manually configure pseudowires. BGP is responsible for distributing the local autodiscovery routes created on each PE device to all other PE devices. LDP is responsible for using the autodiscovery information provided by BGP to set up targeted LDP sessions over which to signal the pseudowires.

3. VPLS BGP Auto discovery and BGP signalling

This implementation uses BGP for both neighbors discovery and signalling.

4. VPLS Mixed LDP and BGP

This is a hybrid implementation where both VPWS and VPLS are combined to offer the best of both worlds.

Configuration samples

Martini L2VPN

Below configuration between Cisco IOS XE and JunOS with existing IP and MPLS underlying configuration

Cisco config and verification

interface Gi0/0/0.1001
  encapsulation dot1q 1001
  xconnect 10.2.2.2 1001 encapsulation mpls
!
show xconnect interface Gi0/0/0.1001
show mpls l2transport vc 1001
show l2vpn atom vc vcid 1001

Altenatively using manual pseudowires

interface Gi0/0/0
  service instance 1001 ethernet
    encapsulation dot1q 1001
!
interface pseudowire 1001
  neighbor 10.2.2.2 1001
  encapsulation mpls
  signaling protocol ldp
! 
l2vpn xconnect context L2C-1001 
  member Gi0/0/0 service-instance 1001
  member pseudowire 1001

show l2vpn service xconnect all
show l2vpn atom vc

Cisco IOSXR

interface GigabitEthernet0/0/0/0.1001 l2transport
 encapsulation dot1q 1001
!
l2vpn
 xconnect group L2CIRCUIT
  p2p VLAN-1001
   interface GigabitEthernet0/0/0/0.1001
   neighbor 10.2.2.2 pw-id 1

 sh l2vpn xconnect 
 

JunOS config and verification

set interface ge-0/0/0.1001 vlan-id 1001
set interface ge-0/0/0.1001 encapsulation vlan-ccc
set protocols l2cicuit neighbour 10.1.1.1 interface ge-0/0/0.1001 virtual-circuit-id 1001

show l2circuit connection interface ge-0/0/0.1001

Local layer 2 circuit

For L2 circuit whose ends terminate on the same router, that is, two different logical interfaces(or physical) for both ends are configured on the same router there is a number of options to go about it as listed below:

• Interface-switch
• Bridge-domain
• local-switching

Interface-switch

This JunOS feature allows for configuration of Layer 2 switching cross-connects. The cross-connect is bidirectional, so packets received on the first interface are transmitted out the second interface, and those received on the second interface are transmitted out the first. For Layer 2 switching cross-connects to work, you must also configure MPLS. The interface-switch can only be configured between two interfaces not more as it does not involve learning of mac addresses and it simply mirrors traffic between the two interfaces if you will.

Configuration:

 set protocols connections interface-switch SAMPLE interface ge-1/0/8.259
 set protocols connections interface-switch SAMPLE interface ge-1/1/2.259
 set interfaces ge-1/0/8 unit 259 description SITE1
 set interfaces ge-1/0/8 unit 259 encapsulation vlan-ccc
 set interfaces ge-1/0/8 unit 259 family ccc
 set interfaces ge-1/1/2 unit 259 description SITE2
 set interfaces ge-1/1/2 unit 259 encapsulation vlan-ccc
 set interfaces ge-1/1/2 unit 259 family ccc

show connections interface-switch SAMPLE    
  Connection/Circuit                Type        St      Time last up     # Up trans
 SAMPLE                        if-sw       Up      Sep 11 18:05:38           1
   ge-1/0/8.259                     intf  Up
   ge-1/1/2.259                     intf  Up

Local-switching

JunOS Configuration

set protocols l2circuit local-switching interface ge-0/1/3.4094 end-interface interface ge-0/0/2.4094
set interfaces ge-0/1/3.4094 vlan-id 4094 encapsulation vlan-ccc family ccc
set interfaces ge-0/0/2.4094 vlan-id 4094 encapsulation vlan-ccc family ccc

Cisco IOS configuration

interface GigabitEthernet1.4094
  encapsulation dot1q 4094
!
interface Gigabitthernet2.4094
  encapsulation dot1q 4094
!
connect TEST Gig1.4094 Gig2.4094

sh connection name TEST
Connection: 4 - TEST
 Current State: ADMIN UP
 Segment 1: GigabitEthernet1.4094 up
 Segment 2: GigabitEthernet2.4094 up

sh xconnect name TEST

Cisco IOSXR configuration

interface GigabitEthernet0/0/0/0.1000 l2transport
 encapsulation dot1q 1000
!
interface GigabitEthernet0/0/0/1.1000 l2transport
 encapsulation dot1q 1000
!
l2vpn
 xconnect group LOCAL
  p2p SWITCH
   interface GigabitEthernet0/0/0/0.1000
   interface GigabitEthernet0/0/0/1.1000

 sh l2vpn xconnect 
 

VPWS Kompella using BGP auto-discovery and signalling

This implementation is not supported by Cisco

JunOS Configuration

set protocols bgp group ibgp family l2vpn signaling

set routing-instances l2vpn instance-type l2vpn
set routing-instances l2vpn interface ge-0/0/1.0
set routing-instances l2vpn route-distinguisher 64512:1000
set routing-instances l2vpn vrf-target target:64512:1000
set routing-instances l2vpn protocols l2vpn encapsulation-type ethernet
set routing-instances l2vpn protocols l2vpn site 1 site-identifier 1
set routing-instances l2vpn protocols l2vpn site 1 interface ge0/0/1.0 remote-site-id 2

show route table L2VPN.l2vpn.0
show l2vpn connections up

VPLS Manual discovery and LDP signalling FEC128

Cisco IOS config and verification

l2 vfi VPLS manual 
 vpn id 1000
 bridge-domain 1000
 mtu 1500
 neighbor 10.2.2.2 encapsulation mpls 
 neighbor 10.3.3.3 encapsulation mpls

interface GigabitEthernet1
 no ip address
service instance 1000 ethernet
  encapsulation dot1q 1000
  rewrite ingress tag pop 1 symmetric
  bridge-domain 1000

show l2vpn vfi name VPLS
show mpls l2transport vc 1000
show xconnect name VPLS
show bridge-domain 1000 mac dynamic address

Altenatively using manual pseudowires

interface GigabitEthernet1
  service instance 1000 ethernet
    encapsulation dot1q 1000
!
interface pseudowire 2
  neighbor 10.2.2.2 1000
  encapsulation mpls
!
interface pseudowire 3
  neighbor 10.3.3.3 1000
  encapsulation mpls
!
l2vpn vfi context VPLS
  vpn id 1000
  member pseudowire 2
  member pseudowire 3
!
bridge-domain 1000
  member GigabitEthernet1 service-instance 1000
  member vfi VPLS

show l2vpn service xconnect all
show l2vpn atom vc

Cisco IOSXR

l2vpn
 bridge group VPLS
  bridge-domain VLAN-1000
   interface GigabitEthernet0/0/0/1.1000
   !
   vfi VPLS-VLAN-1000
    neighbor 10.2.2.2 pw-id 3
    neighbor 10.3.3.3 pw-id 3

JunOS config and verification

set interfaces ge-0/0/2 vlan-tagging
set interfaces ge-0/0/2 encapsulation flexible-ethernet-services
set interfaces ge-0/0/2 unit 1000 encapsulation vlan-vpls
set interfaces ge-0/0/2 unit 1000 vlan-id 1000
set interfaces ge-0/0/2 unit 1000 input-vlan-map pop
set interfaces ge-0/0/2 unit 1000 output-vlan-map push
set interfaces ge-0/0/2 unit 1000 family vpls
set routing-instances VPLS instance-type vpls
set routing-instances VPLS interface ge-0/0/2.1000
set routing-instances VPLS protocols vpls encapsulation-type ethernet
set routing-instances VPLS protocols vpls no-control-word
set routing-instances VPLS protocols vpls no-tunnel-services
set routing-instances VPLS protocols vpls vpls-id 1000
set routing-instances VPLS protocols vpls mtu 1500
set routing-instances VPLS protocols vpls neighbor 10.1.1.1
set routing-instances VPLS protocols vpls neighbor 10.3.3.3

show vpls connections instance VPLS
show vpls mac-table instance VPLS

VPLS BGP Auto discovery and LDP signalling FEC129

JunOS config

set protocols bgp group ibgp type internal
set protocols bgp group ibgp local-address 1.1.1.1
set protocols bgp group ibgp family inet-vpn unicast
set protocols bgp group ibgp family l2vpn auto-discovery-only
set protocols bgp group ibgp neighbor 1.1.1.2 local-as 65000

set interfaces ge-1/3/2 encapsulation ethernet-vpls
set interfaces ge-1/3/2 unit 0 family vpls

set routing-instances vlan100 instance-type vpls
set routing-instances vlan100 interface ge-1/3/2.0
set routing-instances vlan100 route-distinguisher 1.1.1.1:100
set routing-instances vlan100 l2vpn-id l2vpn-id:65000:100
set routing-instances vlan100 vrf-target target:65000:100
set routing-instances vlan100 protocols vpls no-tunnel-services

IOS config

l2vpn vfi context vpls1 
 vpn id 100
 autodiscovery bgp signaling ldp
 exit

router bgp 1
 no bgp default ipv4-unicast
 bgp log-neighbor-changes
 bgp update-delay 1
 neighbor 10.1.1.2 remote-as 1
 neighbor 10.1.1.2 update-source Loopback1  
 address-family l2vpn vpls
 neighbor 10.1.1.2 activate
 neighbor 10.1.1.2 send-community extended  
exit-address-family 

> The RD is taken from [ASN:vpn id], unless a RD is explicitely configured. Here, the RD is 1:100. ### IOSXR config

router bgp 65000
 neighbor-group ibgp-pe
  remote-as 65000
  update-source Loopback0
  address-family l2vpn vpls-vpws
  exit
 !
 neighbor 1.1.1.1
  use neighbor-group ibgp-pe
!
l2vpn
 bridge group v100
  bridge-domain v100
   interface Gig0/0/0/0.100
   vfi v100
    vpn-id 100
    autodiscovery bgp
     rd auto
     route-target import 65000:100
     route-target export 65000:100
     signaling-protocol ldp
      vpls-id 65000:100
!
interface Gig0/0/0/0.100 l2transport
 encapsulation dot1q 100
 rewrite ingress tag pop 1 symmetric

VPLS BGP Auto discovery and BGP signalling

JunOS config

set protocols mpls interface ge-1/3/0.0
set protocols ldp interface ge-1/3/0.0
set protocols ldp interface lo0.0

set protocols bgp group ibgp type internal
set protocols bgp group ibgp local-address 1.1.1.1
set protocols bgp group ibgp family inet-vpn unicast
set protocols bgp group ibgp family l2vpn signaling
set protocols bgp group ibgp neighbor 1.1.1.2 local-as 65000

set interfaces ge-1/3/2 encapsulation ethernet-vpls
set interfaces ge-1/3/2 unit 0 family vpls

set routing-instance vlan100 instance-type vpls
set routing-instance vlan100 interface ge-1/3/2.0
set routing-instance vlan100 route-distinguisher 1.1.1.1:100
set routing-instance vlan100 vrf-target target:65000:100
set routing-instance vlan100 protocols vpls
set routing-instance vlan100 protocols vpls site-range 8
set routing-instance vlan100 protocols vpls no-tunnel-service
set routing-instance vlan100 protocols vpls site my_site site-identifier 2
set routing-instance vlan100 protocols vpls site my_site interface ge-1/3/2.0

IOSXR config

router bgp 65000
 neighbor-group ibgp-pe
  remote-as 65000
  update-source Loopback0
  address-family l2vpn vpls-vpws
   signalling ldp disable
!
 neighbor 1.1.1.1
  use neighbor-group ibgp-pe
!
l2vpn
 autodiscovery bgp
  signaling-protocol bgp
   mtu mismatch ignore
!
 bridge group v100
  bridge-domain v100
   interface TenGigE0/0/0/0.100
   vfi v100
    vpn-id 100
    autodiscovery bgp
     rd auto
     route-target import 65000:100
     route-target export 65000:100
     signaling-protocol bgp
      ve-id 5
      ve-range 11
!
interface TenGigE0/0/0/0.100 l2transport
 encapsulation dot1q 100
 rewrite ingress tag pop 1 symmetric

IOS Config

l2vpn vfi context one
 vpn id 100
 autodiscovery bgp signaling bgp 
  ve id 1001
  ve range 50
  route-target export 32:64
  route-target import 32:64
!
mpls label range 10000 20000
!
bridge-domain 1
 member Ethernet0/0 service-instance 100
 member vfi one
!
l2 router-id 10.100.1.1
!
interface Ethernet0/0
 no ip address
 service instance 100 ethernet
!
router bgp 1
 bgp log-neighbor-changes
 neighbor 10.100.1.4 remote-as 1
 neighbor 10.100.1.4 update-source Loopback0
 !
 address-family l2vpn vpls
  neighbor 10.100.1.4 activate
  neighbor 10.100.1.4 send-community extended
  neighbor 10.100.1.4 suppress-signaling-protocol ldp
 exit-address-family
 

References

https://blog.marquis.co/layer-2-vpns-on-junos/
https://mellowd.co.uk/ccie/l2vpn-on-junos-using-cccmartinikompella/
https://www.inetzero.com/vpls-some-simples-configurations/
https://networkzblogger.com/2017/05/03/mpls-l2vpn-configuration-example-juniper-l2circuit-mpls-l2vpn-tutorial-what-is-l2vpn-l2vpn-wiki-how-l2vpn-works-l2vpn-juniper-kompella/
https://www.cisco.com/c/en/us/support/docs/ios-nx-os-software/virtual-private-lan-services-vpls/116121-tech-vpls-bgp-00.html#anc7
https://null.53bits.co.uk/index.php?page=vpls-ios-xr-to-junos