im shifting a new fmc+ftd instead of an old asa firewall , i was wondering after i shift the new fmc+ftd with the same inside and outside ip addresses if i need to clear arp my layer 3 core switch and my isp router?
if it cisco the default timeout is 4 hours. from experience in term of deployment I have seen issue with connectivity in regards to firewall when inside going outside and when outside ip access the DMZ address.
if you have a change windows which i guess you will have than you can clear the arp entries.
I've definitely run into that issue with ISPs. Most of the ones I've worked with have an arp timeout of 1 hour.
If you haven't opened a ticket with them proactively it takes about that long to get an actual technician ...at which point you end up saying "never mind it just started working".
If you can get the tech on the line in advance you can cut down the outage time significantly.
@Marvin Rhoads agree with you. ISP take time to get this done as you have to log a ticket with them and then chase this up. however, it also depends some ISP are very pro-active and it could be done in 2 day time but some take very long time almost week too.