Layer 3 Mobility - Brocade Communications Systems RFS6000 System Reference Manual

Layer 3 mobility

Refer to the following sections to configure Layer 3 Mobility:
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Configuring layer 3 mobility
Layer 3 mobility is a mechanism enabling a Client to maintain the same Layer 3 address while
roaming throughout a multi-VLAN network. This enables transparent routing of IP datagrams to
Clients during their movement, so data sessions can be maintained while they roam (in for voice
applications in particular). Layer 3 mobility maintains TCP/UDP sessions in spite of roaming among
different IP subnets.
A mobility domain comprises of a network of controllers among which an Client can roam
seamlessly without changing its IP address. Each controller in the mobility domain needs a mobility
domain string identifier so Clients roaming between controllers can retain their Layer 3 address
and maintain application-layer connectivity.
When a Client enters a mobility domain (by associating with a controller), it is first assigned a home
controller. The home controller is responsible for assigning a VLAN for the Client and
communicating the Client's mobility-related parameters to the other controllers in the mobility
domain. The home controller does not change for the remainder of the Client's presence in the
mobility domain. All data packets transmitted/received by the Client including DHCP and ARP are
tunneled through the home controller. The IP address for the Client is assigned from the VLAN to
which the Client belongs (as determined by the home controller).
The current controller is the controller in the mobility domain an Client is currently associated to.
The current controller changes as the Client roams and establishes different associations. The
current controller is responsible for delivering data packets from the Client to its home controller
and vice-versa.
CAUTION
An Access Point is required to have a DHCP provided IP address before attempting layer 3
adoption, otherwise it will not work. Additionally, the Access Point must be able to find the IP
addresses of the controllers on the network.
To locate controller IP addresses on the network:
- Configure DHCP option 189 to specify each controller IP address.
- Configure a DNS Server to resolve an existing name into the IP of the controller. The Access
Point has to get DNS server information as part of its DHCP information. The default DNS name
requested is "Brocade-CAPWAP-Address". However, since the default name is configurable, it can
be set as a factory default to whatever value is needed.
Key aspects of Layer 3 Mobility include:
Brocade Mobility RFS6000 and RFS7000 System Reference Guide
53-1001858-01
Configuring layer 3 mobility
Defining the layer 3 peer list
Reviewing layer 3 peer list statistics
Reviewing layer 3 client status
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Layer 3 mobility
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