1. Configuration Guide
  2. High Availability Nodes
  3. Limiting the Rate of Gratuitous ARP (GARP)

Limiting the Rate of Gratuitous ARP (GARP)

You can configure the Oracle Communications Session Border Controller (SBC) to minimize the rate of IPv4 GARP and IPv6 Neighbor Discovery (ND) traffic it sends out during a failover. This can prevent address resolution errors, caused by slow switching infrastructure. If you do not configure this rate limiting the system sends these messages as fast as possible, based on system load.

When the SBC executes an HA switchover, the new active SBC sends out GARP and/or ND messages for every configured IP address/VLAN pair. To limit the volume of these messages, configure the message window and the number of messages the system sends in this window using redundancy options. No reboot is required. The number of messages is the aggregate of GARPs and NDs. When configured, the system sends the configured number of messages, pauses for the remaining time (configured time minus elapsed time), and repeats the process until all messages are sent.

The garps-per-interval option, specifies the number of messages, from 10 to 1000. If the configured rate exceeds the rate at which the SBC can transmit these messages, the SBC transmits these messages at its maximum rate, without pacing.

The garp-interval option, specifies the message window, from 5 ms 100 milliseconds.

The ACLI example below configures this function to send 500 messages every 50 milliseconds. 

ORACLE(redundancy-config)# options +garps-per-interval 500
ORACLE(redundancy-config)# options +garp-interval 50

Setting the garps-per-interval to 0, the default, disables this function.

Additional configuration considerations include:

  • If you set either parameters to a value smaller than the allowed value, the system sets it to the minimum value.
  • If you set either parameters to a value greater than the allowed value, the system sets it to the maximum value.
  • If you set the garps-per-interval to a nonzero value and do not set the garp-interval, the system uses the minimum value (5ms) for the garp-interval.

Additional operational considerations include:

  • The SBC does not re-transmit messages for any interface until it has sent the initial message for every interface.
  • If configured to send more messages than it can, the SBC ignores the configuration and sends as many as it can.