Planning for migrating a firewall

While coordinating on downtime / planning for migrating to a new firewall, it makes sense to have following information :

From when to when is the downtime?
Who is the contact person available during downtime to help with:
- Cable identification (ISP1 cable, LAN cable, etc.) locally on site
- Coordiante with local users on the site if and when services are disrupted during downtime.
- Test after migration whether all critical services are up.
  - The point of contact must know what are all critical to the site and how to check them. Or he should know who to reach *during* downtime for the validation. Examples to check *not exhaustive*:
    - VPN and appropriate VPN policies
    - Incoming NAT to servers. Also combine this with ISP failover test mentioned later, if applicable.
    - Outgoing Internet access for users and servers with appropriate site blocking
    - IPSec connectivity to other units various subnets. Connectivity to various subnets of unit being migrated from other units.
    - Local logins or AD integration
    - Captive portal (if implemented)
    - Active/Passive failover if deployed in HA
    - ISP failover tests, if applicable
  - For every critical test ensure that the same is done on existing firewall and details are captured (Eg screenshot, URL, whether test is done over public Internet / VPN, etc.)
Is this migration necessary before a specific date? Eg before important event or before current license expires. If yes, please share the date?
What other downtime windows are possible before the migration end-date, if migration fails in the current downtime window.

Anonymous