Warning message

  • Cisco Support Forums is in Read Only mode while the site is being migrated.
  • Cisco Support Forums is in Read Only mode while the site is being migrated.

ASA 5505 - Static ISP address and Mac address off switch ports

Unanswered Question
Sep 11th, 2013
User Badges:


I´m having problems in configure my ISP Static address.

After reading I know that ASA 5505 share phisical mac address to all ports off the switch. And in ASDM I access to the interface and in advanced option is possible to configure one mac.

But when I run sh interface ethernet in every port, shows the same mac. But whith the sh interface vlan 1, shows the mac inserted manualy.

Which of the macs should I give to my ISP? The phisical interface or the vlan interface?

If I change the VLAN mac, isn´t that mac that is fixed to the layer 2 datagram?

Kind Regards,


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Jouni Forss Wed, 09/11/2013 - 18:17
User Badges:
  • Super Bronze, 10000 points or more


It should me the MAC Address of the Vlan interface.

I tested this once for someone here on the CSC when they were having a problem when they replaced the firewall and lost connectivity because ISP still had the wrong ARP table information (same public IP but different MAC)

I for example confirmed that I could configure the same MAC address that they had to my ASA5505 and see that at our ISP core devices ARP table (I work for the ISP)

- Jouni

Antonio Simoes Wed, 09/11/2013 - 18:22
User Badges:

Hi Jouni,

But I changed it too in the interface option, but the ping didnt pass. I will talk to their support, maybe thay have extra security methods or sometihng.

Kind Regards,



This Discussion