How to enable ECS and set custom ECS for specefic domains?

[EliteSalman]

Hi,
I want to set custom ECS for tiktokcdn.com only how can I do that?

[ShreyasZare]

Thanks for asking. I am not sure what custom ECS really means. ECS when enabled will work for all domain names and it will be used only if the clients are accessing the DNS server over public IP addresses. For local networks, ECS does really nothing.

[bingfenghd]

If the goal is "different ECS client subnet for tiktokcdn.com than for everything else," that is usually not a single global ECS toggle.

Typical patterns:

1. Split by recursive forwarder: create a Conditional Forwarder / zone-specific forwarder for tiktokcdn.com (and parents if needed) that points at a resolver path where you control ECS (or where the upstream already applies the subnet you want), while the default recursion path keeps your normal ECS setting.
2. Do not expect per-qname ECS rewrite inside one recursive process unless the product exposes an explicit "ECS override by domain" policy—most resolvers apply one ECS policy to all queries on that listener.
3. Verify with dig: compare answers for the same name with/without +subnet= from a public client IP vs LAN IP (as the maintainer noted, ECS is often ignored/useless on private-client queries).

So: enable ECS globally if you need it at all, then isolate the special domain via conditional forwarding (or a dedicated recursive instance) rather than hunting for a per-domain ECS knob that may not exist.