On 6/8/2016 10:15 AM, David DeSimone wrote:
One of the purposes of the CARP announcements is to announce the
location of the virtual mac address to the upstream switch fabric.
Since CARP uses a virtual mac that floats between multiple ports, you
need to have the CARP master continually assert that its particular
port is the target that should be used for delivery of packets to the
virtual MAC address. Without this function, switches might still
mistakenly deliver their frames to the standby node.
The CARP announcements are also helpful in detecting and routing
around some odd failure scenarios, such as a failure within the
upstream fabric, where the master sees link on its port, but can't
actually send frames that reach the rest of the network. If the
standby can't hear the master's announcements any more, it can
promote itself to master and hopefully keep your cluster online.
This would not happen without the announcement feature.
I would hope you could explain this to your provider and get them to
white-list CARP announcements because they are defeating important
safety features you wish to use.
You just need a gratuitous ARP on the new switch port after the MAC is
migrated. That's how VMs move quickly between hypervisors with almost no
downtime. As soon as a MAC is seen on a new port, the switch should
overwrite it's notion of the port to MAC association.
https://wiki.wireshark.org/Gratuitous_ARP
As for the standby node, it should never announce unless the master node
fails to suppress it.
-Matthew
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