Purpose
Command or Action
This is an example configuration of cross-connect on an EFP interface:
interface gigabitethernet 0/0/3
service instance 30 ethernet
encap dot1q x second dot1q y
xconnect <10.10.10.10> 123 encapsulation mpls
MAC Address Forwarding, Learning and Aging on EFPs
•
Layer 2 forwarding is based on the bridge domain ID and the destination MAC address. The frame is
forwarded to an EFP if the binding between the bridge domain, destination MAC address, and EFP is
known. Otherwise, the frame is flooded to all the EFPs or ports in the bridge domain.
•
MAC address learning is based on bridge domain ID, source MAC addresses, and logical port number.
MAC addresses are managed per bridge domain when the incoming packet is examined and matched
against the EFPs configured on the interface. If there is no EFP configured, the bridge domain ID equal
to the outer-most VLAN tag is used as forwarding and learning look-up key.
If there is no matching entry in the Layer 2 forwarding table for the ingress frame, the frame is flooded
to all the ports within the bridge domain. Flooding within the bridge domain occurs for unknown unicast,
unknown multicast, and broadcast.
•
Dynamic addresses are addresses learned from the source MAC address when the frame enters the router.
All unknown source MAC addresses are sent to the CPU along with ingress logical port number and
bridge domain ID for learning. Once the MAC address is learned, the subsequent frame with the
destination MAC address is forwarded to the learned port. When a MAC address moves to a different
port, the Layer 2 forwarding entry is updated with the corresponding port.
The router does not currently support the
no mac address-table
learning bridge-domain
bridge-id
global configuration command.
Note
•
Dynamic addresses are aged out if there is no frame from the host with the MAC address. If the aged-out
frame is received by the switch, it is flooded to the EFPs in the bridge domain and the Layer 2 forwarding
entry is created again. The default for aging dynamic addresses is 5 minutes. However, when MST
undergoes a topology change, the aging time is reduced to the
forward-delay
time configured by the
spanning tree. The aging time reverts back to the last configured value when the topology change expires.
You can configure a dynamic address aging time per bridge domain using the
mac aging-time time
command. The range is in seconds and valid values are 10-600. The default value is 300. An aging time
of 0 means that the address aging is disabled.
•
MAC address movement is detected when the host moves from one port to another. If a host moves to
another port or EFP, the learning lookup for the installed entry fails because the ingress logical port
number does not match and a new learning cache entry is created. The detection of MAC address
movement is disabled for static MAC addresses where the forwarding behavior is configured by the
user.
Carrier Ethernet Configuration Guide (Cisco ASR 920 Series)
42
Ethernet Virtual Connections Configuration
Configuring IEEE 802.1Q Tunneling and Layer 2 Protocol Tunneling Using EFPs
