Secondary IP On Cisco ASA

While decommissioning some old routers, I need to transfer an IP address to an ASA on a subnet. Unfortunately the ASA’s don’t allow you to do this. The standard “ip address X.X.X.X Y.Y.Y.Y secondary” doesn’t work.

I did a quick google and this beautiful bastard had the solution, static ARP with proxy-arp.

Figure out what the existing MAC is on the interface by issuing;

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show interface

Then use that mac address along with proxy ARP for your secondary IP:

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arp DMZ 192.168.3.3 0000.1111.2222 alias

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