Configuring layer 3 mobility – Brocade Mobility RFS7000-GR Controller System Reference Guide (Supporting software release 4.1.0.0-040GR and later) User Manual
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Brocade Mobility RFS7000-GR Controller System Reference Guide
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Layer 3 Mobility
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Configuring Layer 3 Mobility
Layer 3 mobility is a mechanism enabling a MU to maintain the same Layer 3 address while
roaming throughout a multi-VLAN network. This enables transparent routing of IP datagrams to
MUs 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 switches among which an MU can roam seamlessly
without changing its IP address. Each switch in the mobility domain needs a mobility domain string
identifier so MUs roaming between switches can retain their Layer 3 address and maintain
application-layer connectivity.
When a MU enters a mobility domain (by associating with a switch), it is first assigned a home
switch. The home switch is responsible for assigning a VLAN for the MU and communicating the
MU's mobility-related parameters to the other switches in the mobility domain. The home switch
does not change for the remainder of the MU's presence in the mobility domain. All data packets
transmitted/received by the MU including DHCP and ARP are tunneled through the home switch.
The IP address for the MU is assigned from the VLAN to which the MU belongs (as determined by
the home switch).
The current switch is the switch in the mobility domain an MU is currently associated to. The
current switch changes as the MU roams and establishes different associations. The current switch
is responsible for delivering data packets from the MU to its home switch and vice-versa.
NOTE
An Access Port is required to have a DHCP provided IP address before attempting layer 3 adoption,
otherwise it will not work. Additionally, the Access Port must be able to find the IP addresses of the
switches on the network.
To locate switch IP addresses on the network:
- Configure DHCP option 189 to specify each switch IP address.
- Configure a DNS Server to resolve an existing name into the IP of the switch. The Access Port has
to get DNS server information as part of its DHCP information. The default DNS name requested by
a Brocade Mobility 7131N-FGR Access Point is “Symbol-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:
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Seamless MU roaming between switches on different Layer 3 subnets, while retaining the
same IP address.
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Static configuration of mobility peer switches.
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Layer 3 support does not require any changes to the MU. In comparison, other solutions
require special functionality and software on the MU. This creates numerous inter-working
problems with working with MUs from different legacy devices which do not support Layer 2
switching.
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Support for a maximum of 20 peers, each handling up to a maximum of 500 MUs.
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A full mesh of GRE tunnels can be established between mobility peers. Each tunnel is between
a pair of switches and can handle data traffic for all MUs (for all VLANs) associated directly or
indirectly with the MU.