This is strange requirement but thought let me ask if some has good advice, so we have Linux iptables firewall with 3 interface, public, Internal and DMZ now we decided to replace linux firewall with Cisco ASA 5585, Its production environment. Plan is to take over IP so i will shutdown Linux firewall and put its IP address on ASA so how much time it will take to flush all ARP cache on entire network? I can change IP address in 1 min but i am not sure how long all system and switches will take to flush their arp table and learn new MAC, all the clients are linux base. any advice?
ARP Flush – Manual Broadcast After IP Change
ciscocisco-asafirewalllinuxswitch
Best Answer
E.g. Windows uses 30 seconds for ARP cache timeout. [1]
You might be able to decrease the "dead" time by sending out a gratuitous ARP with the new MAC which the ASA should be doing by itself when changing the IP address, according to [2]:
"When you configure an IP address on the interface, a gratious arp is sent for that IP. If you cycle through all IPs that you use for NAT on the interface, then the other devices get updated for all these addresses."