Each virtual router is configured with a message interval per VRID within which it participates. This parameter must be the same for every virtual router on the VRID.
For IPv4, the default advertisement interval is 1 s and can be configured between 100 ms and 255 s 900 ms. For IPv6, the default advertisement interval is 1 s and can be configured between 100 ms and 40 s 950 ms.
As specified in the RFC, the advertisement interval field in every received VRRP advertisement message must match the locally configured advertisement interval. If a mismatch occurs, depending on the inherit configuration, the current master's advertisement interval setting can be used to operationally override the locally configured advertisement interval setting. If the current master changes, the new master setting is used. If the local virtual router becomes master, the locally configured advertisement interval is enforced.
If a VRRP advertisement message is received with an advertisement interval set to a value different from the local value and the inherit parameter is disabled, the message is discarded without processing.
The master virtual router on a VRID uses the advertisement interval to load the advertisement timer, specifying when to send the next VRRP advertisement message. Each backup virtual router on a VRID uses the advertisement interval (with the configured local priority) to determine the master down timer value.
VRRP advertisement messages that are fragmented, or contain IP options (IPv4), or contain extension headers (IPv6) require a longer message interval to be configured.