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FAQ: Resource Quality Assistance

Show or Hide answer What can I do if my address block is filtered?

If you think your address blocks have been filtered, it is very important to determine how your IP addresses are being blocked:

Run a traceroute to see if the new IP addresses are consistently blocked along the same network path. We also advise you to test forward and reverse paths. The use of technology like the Routing Information Service (RIS) is highly recommended to assist in identifying routing conditions for prefixes under test. RIS is a RIPE NCC project that collects and stores Internet routing data from several locations around the globe. One of the services we provide de-bogonises new IP address blocks to test reachability and view statistics for the visibility of new address blocks over the Internet.

Do a search on your IP addresses and contact organisations that appear to be blocking you. You may be blocked by a technology called DNSBL (DNS-based Blackhole List), due to malicious activities of one of your customers.

If you set up your servers to block bogon IP address ranges, your own firewall might be blocking the new IP addresses by default. To avoid blocking potential new customers, stay on top of changes to that list because new IP address ranges are constantly released.

Use a looking glass service as part of the diagnostic toolset to detect network filters.

Be sure to contact networks that are blocking your IP addresses and request that they remove the filter that is affecting your network traffic. Look up their contact address in the relevant Regional Internet Registry (RIR) whois database. If the contact address is invalid, please notify the appropriate registry.

Show or Hide answer What can I do if my range is blacklisted?

First identify if there is any malicious activity coming from your network and take appropriate action. There are several tools available online, such as the RIPEstat Blacklist Entries widget. If you are sure that there is no malicious activity within your network then contact the operator of the blacklist-file and ask for delisting.

Show or Hide answer How can I manage my filter responsibly?

Filters must be frequently updated to avoid blocking legitimate traffic from your network. There are several organisations on the Internet that provide daily updated bogon and blacklist filters. When all IPv4 address space is eventually allocated, network operators might consider ceasing bogon filtering and only filter statically private and reserved IP address space.

Show or Hide answer What is a bogon prefix?

A bogon prefix as defined by Cymru is “a route that should never appear in the Internet routing table.” When there is no unallocated IPv4 address space left, only private and reserved IP address space (such as 10/8 or 240/4) will remain and this should be statically filtered.

Show or Hide answer Why are bogons filtered?

A packet routed over the public Internet should never have a source address in a bogon range. These are commonly found as the source addresses of DDoS attacks. Filtering these addresses will greatly reduce the impact of such attacks.

Show or Hide answer Can I return my block of IP address space if it gets filtered?

No. RIRs such as the RIPE NCC are responsible for the allocation and assignment of IP address space, but not for the routability of address space.

You should contact the networks that are blocking your IP addresses and request that they remove the filter affecting your network traffic. If you have problems identifying the networks that are blocking you, or you don't receive a response from them, the RIPE NCC will assist you and try to establish a direct contact between the impacted parties. For help with this, send an email to