Mff Operation Modes; Mff Working Mechanism; Protocols And Standards; Configuring Mff - HP 5920 Series Configuration Manual

MFF operation modes

The manual mode applies to networks where IP addresses are statically assigned to the hosts, and the
hosts cannot obtain the gateway information through DHCP. A VLAN maintains only the MAC address
of the default gateway.
In manual mode, after receiving an ARP request for a host's MAC address from the gateway, the MFF
device directly replies the host's MAC address to the gateway according to the ARP snooping entries.
After learning the gateway's MAC address and then receiving an ARP packet with a different source
MAC address from the default gateway, the MFF device will replace the old MAC address with the new
one.

MFF working mechanism

Hosts connecting to an MFF device use the ARP fast-reply mechanism for Layer 3 communication. This
mechanism helps reduce the number of broadcast messages.
The MFF device processes ARP packets as follows:
After receiving an ARP request from a host, the MFF device sends the MAC address of the
•
corresponding gateway to the host. In this way, hosts in the network have to communicate at Layer
3 through a gateway.
• After receiving an ARP request from a gateway, the MFF device sends the requested host's MAC
address to the gateway if the corresponding entry is available; if the entry is not available, the MFF
device will forward the ARP request.
The MFF device forwards ARP replies between hosts and gateways.
•
If the source MAC addresses of ARP requests from gateways are different from those recorded, the
•
MFF device updates and broadcasts the IP and MAC addresses of the gateways.

Protocols and standards

RFC 4562, MAC-Forced Forwarding

Configuring MFF

Enabling MFF

In MFF manual mode, enable ARP snooping on the device.
To enable MFF and specify an MFF operating mode:
Step
1. Enter system view.
2. Enter VLAN view.
3. Enable MFF.
Command
system-view
vlan vlan-id
mac-forced-forwarding
gateway-ip
default-gateway
347
Remarks
N/A
N/A
Use either command.
By default, MFF is disabled.