Which IP Should You Allowlist on a Proxy Server?
Allowlist the source address the proxy actually observes. A laptop's private LAN address is not usually its public source on a remote connection.
Use the source address the proxy sees on the incoming connection. A laptop's Wi-Fi address is not necessarily that address.
For example, a laptop at private address 192.168.1.20 can reach a remote proxy through a NAT router. The proxy normally sees the translated public source, so a rule allowing the laptop's private address will not match. On a private path that preserves it, that same private address can legitimately be the right rule.
Confirm the observation at the proxy's incoming boundary: inspect its connection/access log if you operate it, or use the managed service's documented client-address method. A browser IP-check page is only context because it may use another route. Test the application and path that will actually connect; another proxy, a VPN or a network change can alter the source.
Several devices can share one translated address. An IP rule identifies a network source rather than an individual user, so decide whether authentication is needed as well. If the source changes, arrange a supported update process or authentication policy instead of opening the service to every address.
When applying the rule, verify its position and final default-deny behavior in the installed proxy version, then test permitted and denied sources. Squid access order, for example, can make a later restriction irrelevant. Source permission and destination/port permission remain separate decisions; the right client address does not require allowing it every destination.