Configuring virtual MAC address in Active/standby failover

Answered Question
Oct 30th, 2009

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.



Correct Answer by mkharban about 7 years 3 months ago

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

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Correct Answer
mkharban Fri, 10/30/2009 - 11:14

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

nagabhushana.k Tue, 11/03/2009 - 20:53

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




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