Internet routing
GeoDNS chooses an answer. BGP finds a path.
GeoDNS and BGP operate at different layers. A recursive resolver asks authoritative DNS for an address; after an address is returned, routers use BGP-derived reachability and policy to move packets toward it.
One request, two decisions
- Client asks a recursive resolver.
- Resolver asks Help4 authoritative DNS.
- GeoDNS policy selects an eligible address.
- Resolver caches that answer for its TTL.
- The client connects to the address.
- BGP-derived routing carries packets across networks.
Compare the control planes
GeoDNS seesQuery name, DNS record type, resolver source, optional EDNS Client Subnet, configured geography, health, capacity, and policy.
GeoDNS changesWhich IP address or hostname is returned and for how long it may be cached.
BGP seesIP prefixes, autonomous systems, advertisements, withdrawals, path attributes, and routing policy.
BGP changesWhich network path routers select toward an announced prefix.
Anycast doesAnnounces the same IP prefix from multiple locations; BGP policy selects a path to one announcement.
Why GeoDNS may not choose the physically nearest POP
- The authoritative server usually sees the recursive resolver, not the end user.
- A resolver may be located in another city or use a centralized egress.
- EDNS Client Subnet may be absent, truncated, or intentionally privacy-limited.
- The nearest POP may be drained, unhealthy, full, or disallowed for that site.
- Network latency does not always follow geographic distance.
- A previously cached answer remains until its TTL expires.
GeoDNS and anycast together
A platform can use GeoDNS to choose among regional addresses and use anycast or ordinary BGP inside each address group. GeoDNS provides application-aware answer control; BGP provides network reachability. Neither replaces application health checks, capacity controls, or origin failover.
Important: GeoDNS cannot force every ISP to follow a geographic label, and BGP does not understand page health, sessions, cache state, or application capacity.
Terms
Recursive resolver
Fetches and caches DNS answers for clients.
Authoritative DNS
Serves the source-of-truth zone and routing policy answers.
Autonomous system
A routing domain identified by an ASN that exchanges reachability through BGP.
Prefix
An IP address block advertised or learned by routers.