topic Re: Configuring virtual MAC address in Active/standby failover in Network Security

Configuring virtual MAC address in Active/standby failover

nagabhushana.k — Mon, 11 Mar 2019 16:34:34 GMT

While reading about Failover in ASA, I have come across an interesting topic called "Configuring Virtual MAC address".

According to the Cisco document "In Active/Standby failover, the MAC addresses for the primary unit are always associated with the active

IP addresses. If the secondary unit boots first and becomes active, it uses the burned-in MAC address for

its interfaces. When the primary unit comes online, the secondary unit obtains the MAC addresses from

the primary unit. The change can disrupt network traffic".

My questions are:

Q1: If at all there is a conflict due to MAC address, how does that tie will be broken? I mean, which firewall become active among two?

Q2: Is the above explanation holds good only prior to synchronization between firewalls?

Let me explain a little bit more about my doubt. Let us consider that primary firewall(configured as active) boots first, then the secondary firewall. Due to power failure, Primary firewall fails and secondary takes over as Active.

But when Primary firewalls becomes available, will there be any conflict due MAC address?

I guess it should not be the case. But not able to understand from the perspective of firewalls how they take that decision.

Re: Configuring virtual MAC address in Active/standby failover

mkharban — Fri, 30 Oct 2009 18:14:29 GMT

Hi,

In case of a failover the mac-addresses and the ip addresses are swapped for the devices.

With regards to the scenario you have mentioned whenever the primary device will boot it will obtain mac-addresses originally assigned to the secondary devices leading to no conflict.

Please find below a relative document explaining the same:

http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a00807dac5f.shtml#ACT

Please let me know if this answers our query.

Regards,

Manish

Re: Configuring virtual MAC address in Active/standby failover

nagabhushana.k — Wed, 04 Nov 2009 04:53:58 GMT

Hi Manish,

Thank you for your reply.

Information provided by you has answered my query.

I really appreciate your help in this matter.

Regards,

Nagabhushan

Re: Configuring virtual MAC address in Active/standby failover

davmun001 — Wed, 13 May 2020 19:09:28 GMT

Question for you. What happen when you change the Cisco ASA role.

For example. last 2 weeks, the primary host of my asa cluster fail. So, once i receive my new ASA (RMA), i promoted the secondary to primary. The ASA was already in active state. But once i enter the command failover lan unit primary, communications to the outside have stopped working. All the my server hidden behind a static NAT was no longer available from outside. Why?

My best guest actually is once i enter the command failover lan unit primary, the virtual mac address has changed. Could you please confirm?