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Introduction 25
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 256 gateways, thus providing a design capacity of two million subscribers.
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.
There is currently no failover in support of clustering. The following other NSE features are not compatible
with clustering:

Proxy ARP for device

Routed subscribers
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.