Business Support

BGP Prefix Count Limiting Policy for CenturyLink IQ® Networking

To protect the CenturyLink global network, CenturyLink limits the total BGP (border gateway protocol) route prefix announcements originated by the customer on each IQ Networking Port. A prefix is any BGP route announcement: a summary entry or a specific subnet. The specific limits vary, but are generally as follows. (In some cases, your limits may be configured lower than those below.)

  • IQ Internet Port limit: 800 BGP route prefixes
  • IQ Private Port limit: 1000 BGP route prefixes

For IQ Private Port, this limit is based on a per-BGP session limit and not an entire customer VRF limit. The total the prefix announcements originated by a customer could theoretically contain far more than 1000 entries at central locations.

CenturyLink’s provider edge (PE) routers will automatically drop the BGP session of a customer’s port if more BGP announcements than the prefix limit allows are received by that PE router. This has been more of a concern with IQ Private Port as opposed to IQ Internet Port, but could happen with either. CenturyLink does not have an automated warning system to alert customers of rising prefix counts; the BGP session is dropped without warning once the threshold is exceeded.

To avoid prefix-related BGP session drops, try one of the following solutions:

  1. Summarizing or filtering their BGP announcements from sites with large prefix counts.

  2. Through your account team, request prefix increases for specific IQ Networking ports that require more than 1000 prefix announcements (where you cannot summarize announcements).

    • There is no additional cost for increasing prefix limits on IQ Networking ports, but requests need internal CenturyLink technical review before adjustment. Your CenturyLink account team coordinates the request.

    • CenturyLink does not allow requests for a network-wide prefix increase.

    • CenturyLink understands that there are valid technical reasons for certain sites to advertise large prefix counts and will make every effort to accommodate the requirements of such sites. In extreme cases, PE router regrooms may be required.

If you experience a prefix-related outage and cannot reduce your prefix announcements, please contact the CenturyLink IP TAC and request a temporary prefix increase until your account team can complete the formal prefix increase request process.