Sending Heartbeat Packets With A Configured Mac Address - HP 3500 Series Advanced Traffic Management Manual

Static Virtual LANs (VLANs)
Migrating Layer 3 VLANs Using VLAN MAC Configuration
Sending Heartbeat Packets with a Configured MAC
Address
On the VLAN interfaces of a routing switch, the user-defined MAC address
only applies to inbound traffic. As a result, any connected switches need to
learn the new address that is included in the Ethernet frames of outbound
VLAN traffic transmitted from the routing switch.
If a connected switch does not have the newly configured MAC address of the
routing switch as a destination in its MAC address table, it floods packets to
all of its ports until a return stream allows the switch to learn the correct
destination address. As a result, the performance of the switch is degraded as
it tries to send Ethernet packets to an unknown destination address.
To allow connected switches to learn the user-configured MAC address of a
VLAN interface, the HP routing switch can send periodic heartbeat-like Ether-
net packets. The Ethernet packets contain the configured MAC address as the
source address in the packet header. IP multicast packets or Ethernet service
frames are preferred because they do not interrupt the normal operation of
client devices connected on the segment.
Because the aging time of destination addresses in MAC address tables varies
on network devices, you must also configure a time interval to use for sending
heartbeat packets.
Heartbeat packets are sent at periodic intervals with a specific HP unicast
MAC address in destination field. This MAC address is assigned to HP and is
not used by other non-HP routers. Because the heartbeat packet contains a
unicast MAC address, it does not interrupt host operation. Even if you have
multiple HP switches connected to the network, there is no impact on network
performance because each switch sends heartbeat packets with its configured
MAC address as the destination address.
The format of a heartbeat packet is an extended Ethernet OUI frame with an
extended OUI Ethertype (88B7) and a new protocol identifier in the 5-octet
protocol identifier field.
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