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  • Improved Reliability and Resiliency: Anycast provides improved reliability, because DNS queries are sent to an Anycast IP address. If the nearest server somehow goes offline, the router forwards the request to the next nearest DNS server advertising the target Anycast IP address.
  • OSPF and BGP Protocols: Anycast uses both Open Shortest Path First (OSPF) and Border Gateway Protocol (BGP). 
  • Load Distribution: Anycast distributes the load across multiple DNS servers based on network topology. Dynamic routing enables a fully flexible and path-optimized DNS packet flow.

BloxOne Cloud Infoblox Platform provides multiple Anycast addresses to improve resiliency and reliability. Infoblox recommends that you provision your network firewalls and allow traffic to the following ports:

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To enable anycast for DNS queries, you configure two or more DNS servers within the AS routing domain with the same anycast address. When you select OSPF as the routing protocol, the upstream router determines the nearest server within the group of servers configured with that anycast address. (The "nearest" DNS server may not necessarily be the geographically closest DNS server; it is the DNS server with the lowest cost associated with its reachability from the current node. This is calculated through the OSPF routing algorithm, a discussion of which is far beyond the scope of this manual.) The nearest DNS server configured with the correct anycast address then responds to the DNS query. In the case where the nearest server becomes unavailable, the next nearest server responds to the query. OSPF anycast provides a dynamically routed failover to ensure that DNS can always resolve client requests within the AS. From the client perspective, anycasting is transparent and the group of DNS servers with the anycast address appears to be a single DNS server.

OSPF determines the nearest server within the intranet or enterprise network. The desktop sends a DNS query to 10.128.1.12, the anycast address. (The example also shows a configured IPv6 Anycast address.) Many servers can possess the anycast address. The routing protocol selects the nearest server (based on metrics generated from the routing algorithm), and that server receives and processes the query and sends back the response. The Client sends a DNS query via intranet to various DNS servers. OSPF determines the nearest server within the intranet or enterprise network. The desktop sends a DNS query to 10.128.1.12, the anycast address. (The example also shows a configured IPv6 Anycast address.) Many servers can possess the anycast address. The routing protocol selects the nearest server (based on metrics generated from the routing algorithm), and that server receives and processes the query and sends back the response. The Client sends a DNS query via intranet to various DNS servers. OSPF determines the nearest server within the intranet or enterprise network. The desktop sends a DNS query to 10.128.1.12, the anycast address. (The example also shows a configured IPv6 Anycast address.) Many servers can possess the anycast address. The routing protocol selects the nearest server (based on metrics generated from the routing algorithm), and that server receives and processes the query and sends back the response. The Client sends a DNS query via intranet to various DNS servers. OSPF determines the nearest server within the intranet or enterprise network. The desktop sends a DNS query to 10.128.1.12, the anycast address. (The example also shows a configured IPv6 Anycast address.) Many servers can possess the anycast address. The routing protocol selects the nearest server (based on metrics generated from the routing algorithm), and that server receives and processes the query and sends back the response. The Client sends a DNS query via intranet to various DNS servers.Image Modified

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You can configure anycast addressing on the DNS servers and select BGP as the protocol to advertise the anycast addresses to Router 1 and 2 in AS 65499. For more information, see see Configuring   Anycast   Addresses. Once  Once you have configured the DNS servers, the appliances automatically add filters on the advertising interfaces to limit the advertisements to the configured anycast IP addresses. Similarly, BGP filters are applied to ensure that the DNS servers only receive default route advertisements from the neighboring routers.

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