BGP Route Aggregation and Filtering Policy
What is BGP and How to Use It?
Citynet installs inbound and outbound route filters for all customer Border Gateway Protocol (BGP) sessions. Inbound filters provide additional security, and stability on the network, guaranteeing greater reliability, and reduce the odds of a customer created network event. Filter Policy Please familiarize yourself with the Citynet Route Aggregation and Filter guidelines outlined below:
- Customers should perform their own route filtering before announcing to Citynet.
- Route filter requests sent to Citynet to be placed on the Citynet side of the BGP session should be written as inclusive lists (i.e.. stating what should be permitted).
- Customers desiring changes to their route filters must complete the BGP request form.
- Customers must inform Citynet on all changes in IP block announcements if an IP filter was requested at the time of installation of the BGP session.
- Customer filters will be aggregated if not submitted as so already. This does not materially affect your announcements, it simply reduces the complexity of the route filter.
- Customers may announce routes as small as /24 for IP address blocks obtained through Citynet.
- Peer block announcements and customer announcements for blocks obtained from other providers are limited to a /24 or smaller mask (/23, /22 etc.).
- Citynet can and will take action if a BGP session is causing routing problems. This may include, but is not limited to, imposing a filter change or temporary shutdown of the offending BGP session until the problem is corrected.
- Citynet will filter customer block announcements if the owner of the aggregate block requests in writing that we do so.
- While Citynet provides its best effort to check the validity of a customer's route announcements, it is the responsibility of the customer to maintain correct information.
- Citynet reserves the right to set or convert any and all route filters and filter types at their own discretion to preserve network stability and route sanity.
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