Layer 2 Control Protocols Tunneling
Overview
The Layer 2 Control Protocols (L2CP) processing specified here is based largely on the IEEE 802.1Q specification for handling L2CP Frames, i.e. if they should be forwarded, peered, or discarded.
IEEE 802.1Q provides a mechanism for separating the Layer2 control plane into multiple customer and provider control planes. It allows a certain layer 2 control protocol to operate only within a provider network, or to allow interaction between the customer and the provider network, or to pass transparently through a provider network with complete isolation from other customer networks.
In case of non-PB case, packet is forwarded without changing any MAC.
L2CP Tunneling for Provider Bridging
L2CP tunneling provides support for tunneling control plane frames between CE nodes.
In the context of PB, a L2CP frame is defined as any frame containing a destination MAC address as 01:00:0C:CD:CD:D0 or 01:04:DF:CD:CD:D0 (which can be changed via CLI)
When control frames received at CEP port of a PE bridge, predefined multicast address (01-00-C2-CD-CD-D0) is replaced as destination for tunneling the packets across service provider network. If control packets are customer vlan tagged or untagged, then PE bridge will append corresponding service vlan tag to the control packet as per registration table / vlan translation table mapped to the port and send it across the service provider as a data packet.
When tunneled control packet with multicast address (01-00-C2-CD-CD-D0) received on PNP port, the multicast address is replaced with corresponding control packet multicast address and cvlan/svlan removal or update is done as per registration table / vlan translation table.
L2CP tunneling for provider bridging
L2CP Tunneling for VXLAN
L2CP tunneling provides support for tunneling Control plane frames across VXLAN/MH.
Topology
L2CP tunneling for VXLAN
VXLAN creates LAN segments using a MAC in IP encapsulation. The encapsulation carries the original L2 frame received from a host to the destination in another server using IP tunnels. The endpoints of the virtualized tunnel formed using VXLAN are called VTEPs (VXLAN Tunnel EndPoints).
L2CP tunneling provides support for tunneling control plane frames across VXLAN with MH/SH combination.
Any L2CP frame that is destined towards other end with a multicast destination MAC Address for L2 protocol is decided by looking at the frame and upon the configured values of the L2CP Service Attributes.
As and when Control packets with default destination MAC address for any L2 protocol is generated, it will be forwarded by VTEPs that are part of MH towards the VTEP that is part of SH and vice versa.
During this operation, the default destination MAC address for any L2 protocol is replaced with predefined multicast address as destination for tunneling the packets across SPINE nodes. When tunneled control packet with pre-defined multicast address received on ingress port on the other end of the VTEP, the multicast address is replaced with corresponding control packet multicast address.
Basic Configuration for L2CP on Provider Bridging
Enabling tunneling at interface:
(config)#bridge 1 protocol provider-rstp edge
(config)#vlan database
(config-vlan)#vlan 2-10 bridge 1 state enable
(config-vlan)#vlan 11 type service point-point bridge 1 state enable
(config-vlan)#ex
(config)#cvlan registration table map1 bridge 1
(config-cvlan-registration)#cvlan 2 svlan 11
(config-cvlan-registration)#ex
(config)#interface xe1
(config-if)#switchport
(config-if)#bridge-group 1
(config-if)#switchport mode customer-edge hybrid
(config-if)#switchport customer-edge hybrid allowed vlan all
(config-if)#switchport customer-edge vlan registration map1
(config-if)#l2protocol stp tunnel
#show running-config interface xe1
!
interface xe1
speed 1g
switchport
bridge-group 1
switchport mode customer-edge hybrid
switchport customer-edge hybrid allowed vlan all
switchport customer-edge vlan registration map1
l2protocol stp tunnel
customer-spanning-tree provider-edge svlan 11 path-cost 128
(config-if)#commit
Configuring egress interfaces:
(config)#interface xe2
(config-if)#switchport
(config-if)#bridge-group 1
(config-if)#switchport mode provider-network
(config-if)#switchport provider-network allowed vlan all
(config-if)#commit
To display L2protocol information:
#show l2protocol processing interface xe1
Bridge Interface Name Protocol Processing Status Hardware Status
====== ============== ======== ================= ===============
1 xe1 stp Tunnel Tunnel
1 xe1 lacp Peer Peer
1 xe1 dot1x Peer Peer
1 xe1 lldp Peer Peer
1 xe1 efm Peer Peer
1 xe1 elmi Peer Peer
To display L2protocol counters:
#show l2protocol interface counters
Interface xe1
Tunnel : stp : 45