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Silverline's Internal BGP Propagation for Routed Customers

Silverline's routed service leverages BGP to route customer traffic through scrubbing centers, and back to the customers infrastructure.

A customer's subnet is originated and propagates, via the interconnect method (such as GRE tunnels), to all Silverline scrubbing centers and then on to Silverline transit providers.

Within the Silverlline infrastructure, BGP metrics are applied to ensure every customer route takes the best path once within the Silverline infrastructure. These metrics are not applied to announcements to Silverline carriers.

BGP metrics are added at each Silverline scrubbing center. The metric of the lowest score is considered the best path. Traffic entering a scrubbing center where GRE tunnels are provisioned will always prefer the direct route over the tunnels.

In the below example, an end-user entering a Silverline ASIA scrubbing center via a transit provider located in Asia, will route directly to the Silverline EU scrubbing center over the Silverline backbone where a customer's GRE tunnels are located. 

The above scenario will compare the following routes and applied metrics:

  • ASIA --> EU = 1800
  • ASIA --> US EAST = 2300
  • (ASIA --> US West = 1700) + (US West --> US East = 750) = 2450

The 1800 metric will be determined as the best path.

The above metric numbers are examples, as metrics are determined by a number of factors, including health metrics.

More information around BGP configuration, including information on tunnel preferencing, can be found on BGP Configuration - Guidelines & Tips.

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