F Root

One of the 13 DNS root nodes of the Internet

ISC operates the “F” root domain server, one of the 13 Internet root name servers known as A-root through M-root. We have operated F-Root for IANA since 1994. The Root Server Technical Operations Association maintains a map that shows the location of all of the world’s root name servers. Over 225 of them are F Roots, operated by ISC.


If you are perplexed that over 225 (the number of F-root servers) is greater than 13 (the number of root name servers), you can read about the “anycast” scheme used to make the servers collectively behave as one server. F-root answers queries over IPv4 on, and over IPv6 on 2001:500:2f::f using a hierarchical anycast technique and BIND 9 software. Network operators can improve their access to the F Root Nameserver, and hence the reliability of the DNS in general, by peering with ISC at the exchange points where we maintain a presence.


We have almost 3,000 F-root peers. For information about peering with ISC, see our Peering Information Page.

Hosting F-Root

If you think your users would benefit from the improved DNS stability that a local F Root Server would bring, but there is no F-Root Server listed for your city or region, let us know. We are in the process of adding more sites.

If you are a researcher and your research involves F.root-servers.net in any way, please contact us at f-root@isc.org and we will be happy to provide you with information on many aspects of F-root, first hand.

Our Commitment to F-Root

On January 4th, 2008, ISC became the first root server operator to sign a Mutual Responsibilities Agreement with ICANN, which identifies mutual responsibilities and is another step to enhance Internet stability.


For a current map of F-Root nodes, see the Root Server Technical Operations Association web site and select ‘F’ root at the bottom of the page. For more information and resources about F-Root, such as locations and identifying which F-root is providing service to you, visit our F-Root Resources Page.

Which F-root node am I using?

To ensure that your users have access to an appropriate local root server it can be useful to find out which instance of the F-Root Nameserver you are currently using. If there is a site listed close to you but you do not appear to be using it, ask your ISP to contact us so we can make the local site available to their customers.

To find out which F-Root site is answering your queries, try one or both of the following:

    • traceroute F.ROOT-SERVERS.NET

The route your packets take to reach F should give you some information about which site you are using. The site code used to name the ISC routers at the end of the trace can be looked up in this page.


This command sends a query to the F root nameserver, asking it to reveal the name of the particular server which answers the query. The hostname will contain a site code, allowing the location of the server to be identified. The dig utility is distributed with ISC BIND 9.

Last modified: August 10, 2018 at 1:04 pm