ACCESS GATEWAY
Introduction 29
Multiple Unit Clustering
In the recent past, it was necessary to segment the network to serve a number of subscribers
that exceed the user count on a Nomadix gateway. Now with clustering all subscribers can be
on the same segment, as the subscribers are distributed across multiple gateways. A large
number of subscribers can be distributed to as many as 250 gateways, thus providing a design
capacity of 1 million subscribers being served.
One can scale the cluster up and down just by adding gateways or removing gateways.
Remember that a subscriber and the subscriber’s MAC address are positioned in a specific
gateway, so changing the number of gateways will require the gateways to reconfigure, and
their current subscriber table updated. If a prepaid subscriber exists in a radius or
authentication file, this prepayment will be lost. It is recommended that prepayment situations
should be avoided.
The cluster will distribute the subscribers MAC addresses according to a modulus calculation
based on the last three bytes of the MAC address of the subscriber. The result will determine
which gateway will support that MAC address while the other gateways ignore the traffic for
the MAC.
With the 8.3 release, there is currently no failover in support of clustering. This will be
addressed in later releases.
The following other NSE features are not compatible with clustering:
Proxy ARP for device
Routed subscribers
Intra-port communication
Identifying the Resident Gateway in a Cluster Environment
To diagnose device connection problems in a cluster environment, you must identify the
resident gateway. For a given MAC address, you can determine the gateway as follows. You
will need the last three bytes of the device MAC address and the total number of gateways.
Convert the hex bytes to decimal:
1. Using the Windows Calculator in programmer mode
2. In hex mode, input the last three bytes of the MAC address
3. Convert to decimal by using that function on the calculator
The resident gateway is the (decimal bytes) modulus (the total number of gateways), plus 1.
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