Frequently asked questions

We are constantly working on our FAQs. If you have any question that is not answered below, please contact us!

General FAQs

  • An Internet Exchange (IX) or Internet Exchange Point (IXP) is a physical infrastructure which lets Internet service providers (ISPs), content delivery networks (CDNs), and other network providers exchange Internet traffic with one another, typically on a cost-neutral basis. Being connected to the infrastructure allows each network to connect to other networks and share traffic (also known as “peering”). This reduces costs for the networks because they do not need to pay for transit on all of their Internet traffic. Having direct access to the infrastructure and to the networks you want to peer with reduces latency by reducing the length of the path that traffic needs to travel. In the end, an IX increases the resilience of the Internet by providing many more redundant routes for traffic, allowing congested routes to be avoided. Watch a video explaining what an Internet Exchange is.

  • To help our customers, DE-CIX opened dedicated Cloud Exchanges in metro cities where the hyperscale cloud service providers are also available. The primary purpose of our Cloud Exchanges is to facilitate secure, reliable, and high-performance connectivity between enterprises and cloud providers, bypassing the Internet. By establishing these direct connections, organizations can benefit from enhanced network performance, lower latency, improved data transfer speeds, and increased security.

  • Interconnection is a connection between two or more parties in order to exchange data. In the context of telecommunications, interconnection is a physical link between either a carrier’s network and a data center, or a carrier or ISP and their customers, or between multiple carriers, data centers, ISPs, enterprises etc. But when you look at it not only from the physical point of view, it becomes much bigger: Interconnection stands for “being connected”. Find out more.

  • Latency is the delay between a user’s action and the response to that action from a website or an application – in networking terms, the total round-trip time (RTT) it takes for a data packet to travel. It is measured in milliseconds and Internet quality depends on it – the lower the latency, the better the user experience.

  • An Autonomous System Number (ASN) uniquely identifies every network on the Internet. An Autonomous System (AS) is a group of IP networks operated by one or more network operators, with a single and clearly defined external routing policy. The ASN both identifies the network and enables it to exchange routing information with other ASes. 

    Every Internet service provider (ISP) requires their own ASN, but also the individual organizations that connect to the Internet through an ISP require one. After an application from an organization, ISP or other entity has been approved, ASNs are assigned by regional Internet registries. Any network that wants to peer at a public Internet Exchange must have a public ASN.

    To find out more, download our white paper

  • To peer at an Internet Exchange, you need an ASN, which you can request at one of five regional Internet registries. The DE-CIX Academy video “What is an AS number and how do I get one” explains the basics. DE-CIX itself does not offer consulting services to accompany the process of getting an ASN, but if you have any questions, feel free to approach us at [email protected]. We can either assist you or recommend someone who can.

  • Start by choosing a DE-CIX location where you want to connect. Then, have a look at the cities and data centers where it is possible to connect to your chosen exchange. Choose the data center that best suits your needs. If you have your own PoP, you can use this; otherwise, you can buy a transport connection or get connected via an authorized DE-CIX reseller. You can check here whether you can connect directly or whether a certified DE-CIX reseller can connect you.

    Choose an access size suited to the amount of traffic you have. Fill in our form or request an offer for these specifications by contacting [email protected]. We will send you the DE-CIX agreement and service order form accordingly. As soon as the paperwork is signed, we can get you up and running within a few days.

    More information.

  • All connections to DE-CIX require a single-mode private interconnect (aka cross connect or in-house cabling). A cross connect is a dark fiber point-to-point interconnection. It is used to access the DE-CIX platform.

    You can order cross connects via DE-CIX Internet Exchanges in Barcelona, Chicago, Dallas, Dusseldorf, Frankfurt, Hamburg, Istanbul, Lisbon, Madrid, Marseille, Munich, New York, and Palermo. In select enabled sites in Frankfurt, customers can order cross connects to interconnect networks directly. 

    At the other platforms, DE-CIX will provide all customers with demarcation details in the appropriate data center.  Please talk to your data center operator for details.

Peering FAQs

  • Peering is the exchange of data on a cost-neutral basis. All kinds of networks like carriers, Internet Service Providers (ISPs), and network operators need to exchange data in order for the Internet to work. The data exchange is either agreed on a bilateral payment basis (for transit/upstream) or on a cost-neutral basis (peering). Find out more.

  • IP transit is a service where a network pays another network for Internet access (or transit), also known as upstream.  Peering is when networks exchange traffic between each other freely (settlement-free), and for their mutual benefit.  See our white paper "When to peer and when to use transit" for more information.

  • Border Gateway Protocol (BGP) is a routing protocol designed to exchange routing and reachability information between Autonomous System (AS) networks. BGP manages how data gets delivered between networks. AS networks have BGP-speaking routers that advertise or announce to other BGP-speaking routers they are connected to (called neighbors) the prefixes of IP addresses that they can deliver traffic to. BGP routers then use decision-making algorithms and policies established in AS-peering agreements to analyze the data they gather via the prefix announcements and choose which peer is best to send each packet of data to at any given time. 

    Generally, the fastest path with the fewest number of network hops is selected. Once the data moves across an AS and reaches another BGP router connected to a different AS, the process repeats itself until the data reaches the AS where the destination site is located. 

  • PeeringDB is a nonprofit, member-based organization that facilitates the exchange of user maintained interconnection information, primarily for peering coordinators and Internet Exchange, facility, and network operators.

    Having a well maintained PeeringDB entry is a must-have for all networks engaged in interconnection, especially for all peering administrators. It gives you information about networks and shows other networks who might be interested in peering with you the basic data they need to know.

    If you do not have an entry yet, you can register here for free. If you already have one, we recommend checking your entry from time to time to make sure it's up to date.

  • If you want to know which networks you can reach at our locations, you can search for a company name or AS number or you can check the list of connected networks for each location directly.

    Although more than 2,000 networks peer at DE-CIX’s exchanges, not all ASNs are available. Do you have an ASN you would like to peer with and you cannot find it at our exchanges? Let us know and we will try to bring it to the exchange of your choice. Just fill in our form.

  • Peering offers many benefits, and in general, looking at both quality and costs, it makes sense to peer. But at which Internet Exchange? This question pops up soon after you’ve decided to peer. The criteria you should take into consideration are outlined here

Blackholing FAQs

  • Blackholing is a security measure for protecting a network against a Distributed Denial of Service (DDoS) attack. The method allows packets to a specific network to be “dropped” so that they do not reach the recipient and overload their resources. The network under attack can announce the affected prefixes as blackholes by using the BGP BLACKHOLE community. DE-CIX offers Blackholing at all DE-CIX exchanges, except the IXs in Asia, Moscow, St. Petersburg, and Berlin, free of charge.

  • A blackhole is a prefix for which all destination traffic will be discarded.

  • The amount of blackholes is included in the maximum number of allowed prefixes.
    This means: (standard prefixes + blackholes) < maxpref.

  • The blackhole can be as specific as /32 (IPv4) or /128 (IPv6).

  • Many peers do not accept IPv4 prefixes more specific than /24 and IPv6 prefixes more specific than /48. Please ask your peers to accept more specific prefixes.

  • Please check if your blackhole announcement has been accepted by the route servers. You can check this in the DE-CIX Looking Glass. By entering the blackhole prefix into the global search field, you can get an overview of the networks announcing this blackhole prefix, as well as the route servers and therewith the exchanges where the prefix is visible at. 

  • No. The route servers honor these communities and will not pass on your announcements at all. The route servers will automatically add NO-EXPORT to all blackholes before exporting them to other peers.

  • No. This would have the same effect as NO-EXPORT/NO-ADVERTISE as you instruct the route servers to not advertise your prefix(es) to any peers.

  • Yes, standard DE-CIX route server BGP control communities apply to blackholes as well. You can e.g. signal a blackhole to all route server peers except AS64501 by setting the following communities:

    (6695:6695) where 6695 is the AS of the DE-CIX route servers in Frankfurt. 
    Replace this to the corresponding route server AS of each DE-CIX IX.


    For more information about route server BGP control communities, please have a look at our route server guides.

  • You can check this in the DE-CIX Looking Glass. By entering the blackhole prefix into the global search field, you can get an overview of the networks announcing this blackhole prefix, as well as the route servers and therewith the exchanges where the prefix is visible at. 

  • No, Blackholing is free of charge for customers who use the GlobePEER service.

  • Blackholing is available at all DE-CIX exchanges, except Berlin, Moscow, and the Internet Exchanges in Asia.

Blackholing Advanced

  • Blackholing Advanced is a further development of the well-known standard Blackholing feature. Blackholing Advanced allows you to block not only by prefix, but also by header information such as transport ports. It also solves the blackhole acceptance problem of our standard RTBH feature.

  • The feature is not activated by default. If you want to use the Blackholing Advanced feature, please request activation of the service via [email protected]. After activation, you can use BGP extended communities with your BGP announcements to trigger filters on the DE-CIX switching fabric.

  • Each BGP extended community maps to a specific filter. The full list of filter communities can be found on the DE-CIX portal[SI1] .

     [SI1]Link to

  • A blackhole is a prefix for which all destination traffic can be discarded, shaped, or filtered. Multiple of these actions can be applied to the prefix's traffic (e.g., block all UDP but allow DNS).

  • Blackholes in the context of Blackholing Advanced are not counted by prefixes, but by the number of filter communities attached to prefixes.

    As an example, you can announce 6 prefixes with 3 filter communities each (e.g., drop UDP, allow traceroute, allow DNS), which would amount to 18 filter communities.

    The free tier includes 20 filter communities, that can be announced per peering service. You can buy an upgrade of up to 120 filter communities per peering service. To do so, please contact the Customer Service team.

  • The blackhole can be as specific as /32 (IPv4) or /128 (IPv6). It will be accepted by any DE-CIX GlobePEER route server.

  • Prefixes tagged for Blackholing Advanced are accepted if they are covered by an IRR entry or an RPKI ROA, or both. The maximum prefix length of ROAs is ignored to give you higher flexibility for filtering.

  • Please follow these steps for troubleshooting:

    • Check if your blackhole announcement has been accepted by the route servers. You can check this in the DE-CIX GlobePEER Looking Glass.
    • Please also check your filter limit (see "How man blackholes can I advertise?"); the free tier limit is 20 filter communities. You can upgrade this to up to 120.
    • Check the filter communities you announced against the community list here.
    • If you still see malicious traffic, please contact our customer service via [email protected].
  • No. For more specifics (</24 for IPv4, </48 for IPv6) the routes are not exported to other peers anyway, so only DE-CIX will see them. For less specifics, we export the prefixes by default to avoid breaking routes; this is necessary as Blackholing Advanced allows you to drop unwanted traffic selectively and only forward wanted traffic.

  • No. This would have the same effect as adding NO_EXPORT and/or NO_ADVERTISE.

  • It depends.

    If you announce a more specific (</24 for IPv4, </48 for IPv6), selective export to other peers will not have any effect, as these routes are not exported to other peers. In this case you can do a selective export for a larger prefix containing the blackhole.

    For less specifics, you can announce blackholes with selective export. For more information about route server BGP control communities, please have a look at our route server guides.

  • You can check this in the DE-CIX GlobePEER Looking Glass. By entering the blackhole prefix into the global search field, you can get an overview of the announced filter communities of the prefix and of the route servers, and as a result the exchanges where the prefix is visible.

  • Up to 20 filter communities can be announced free of charge. If you want to get additional filters, we can provide them in various bundles (10 / 100 rules). Up to 120 filter communities per peering service are supported.

  • Blackholing Advanced is currently available in Barcelona, Chicago, Copenhagen, Dallas, Dusseldorf, Esbjerg, Frankfurt, Hamburg, Helsinki, Istanbul, Kristiansand, Leipzig, Lisbon, Madrid, Marseille, Munich, New York, Oslo, Palermo, Phoenix, and Richmond.