All HTTP requests to PayPal get routed to an Application Load Balancer at Amazon Web Services (AWS).
Amazon states that IP addresses for Classic Load Load Balancers and Application Load Balancers change over time. Refrain from using this information to statically configure your AWS applications to point to those IP addresses.
We recommend that you use the IP addresses associated with api.integrator.io, and just whitelist Celigo IPs. To avoid firewall limitations, you can periodically perform manual DNS lookups to ensure that the IP addresses you have are the latest, but this strategy is less efficient.