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Static Virtual LANs (VLANs)
Migrating Layer 3 VLANs Using VLAN MAC Configuration
Migrating Layer 3 VLANs Using VLAN
MAC Configuration
HP routing switches provide an easy way to maintain Layer 3 VLAN configu-
rations when you migrate distribution routers in a network configuration that
is not centrally managed. By following the procedure described in this section,
you can upgrade to HP routing switches without stopping the operation of
attached hosts that use existing routers as their default gateway to route traffic
between VLANs. You can achieve seamless VLAN migration by configuring
the MAC address of the previously installed router on the VLAN interfaces of
an HP routing switch.
VLAN MAC Address Reconfiguration
The HP switches covered by this guide use one unique MAC address for all
VLAN interfaces. If you assign an IP address to a VLAN interface, ARP resolves
the IP address to the MAC address of the routing switch for all incoming
packets.
The Layer 3 VLAN MAC Configuration feature allows you to reconfigure the
MAC address used for VLAN interfaces using the CLI. Packets addressed to
the reconfigured Layer 3 MAC address, such as ARP and IP data packets, are
received and processed by the HP routing switch.
Packets transmitted from the routing switch (packets originating from the
router and forwarded packets) use the original HP MAC address as the source
MAC address in Ethernet headers.
ARP reply packets use the reconfigured MAC address in both the:
â– ARP Sender MAC address field.
â– Source MAC address field in the Ethernet frame header
When you reconfigure the MAC address on a VLAN interface, you may also
specify a keepalive timeout to transmit heartbeat packets that advertise the
new MAC address.
By configuring the MAC address of the previously installed router as the MAC
address of each VLAN interface on an HP switch, you can swap the physical
port of a router to the HP switch after the switch has been properly configured
in the network.
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