Working with BGP Summary Routes

This article explains BGP summary routes and the configuration settings, for Socket sites v19.0, IPsec, and Cloud Interconnect sites.

Overview

BGP summary routes reduce the size of BGP routing tables and improving network scalability. They are commonly used to simplify routing information exchange between AS. By advertising a summary route instead of multiple unique routes, BGP peers can simplify their forwarding decisions and minimize computational resources required for route lookup. Summary routes can enhance BGP synchronization by reducing exchange of large amounts of routing information.

You can optionally add BGP communities to your summary routes to create specific routing policies for the included routes.

Prerequisites for Using BGP Summary Routes

  • For Socket sites, BGP summary routes are supported on Sockets v19.0 and higher

Understanding BGP Summary Routes

BGP summary routes help to reduce BGP overhead and routing table size by minimizing the number of advertised BGP entries over the network. A summary route is advertised as long as at least one of its more specific routes exist in the Socket or PoP's routing table. If this condition is not met, the summary route is withdrawn.

The example below shows the difference between a site in which route prefixes are advertised with or without BGP route summarization.

Without summary routes: When the Socket advertises route prefixes to its neighbor via BGP, it is configured to advertise All Routes - Meaning five unique route prefixes are advertised.

BGP_without_Summary.jpg

With summary routes: The Socket advertises a single Summary Route to its neighbor via BGP. The summary routes aggregates all the five unique routes and advertises them as a single route prefix.

BGP_with_Summary.jpg

BGP Summary Routes Use Cases

  • Overcoming hardcoded limitations for a number of received BGP routes - Some Cloud Providers impose limitations on the amount of route prefixes they can receive. AWS, Microsoft Azure, and other cloud providers limit the number of route prefixes in their environment. For example, Azure sis limited to receive up to 1000 routes only. A BGP summary route can be used to overcome this limitation by minimizing the total amount of advertised route prefixes.

  • Network BGP routing simplification - BGP summary routes can reduce BGP overhead where many routes are advertised across large networks. Replacing many unique route prefix advertisements with a summary route also allows for a simplification of the routes in your account for better management and monitoring of BGP traffic.

Configuring BGP Summary Routes

Configure BGP summary routes to existing BGP peers or create new BGP peers.

This section explains how to edit existing BGP neighbors and add a summary route. For more creating a new BGP neighbor, see Defining BGP Neighbors.

These are the limits for BGP summary routes, you can configure up to:

  • 100 summary routes per BGP peer

  • 5 communities per summary route

Note

Note: Modifying the BGP advertisement configuration, such as BGP summary routes, causes a hard BGP peer reset which can impact end user experience.

Advertising Only BGP Summary Routes

For configurations where you are only advertising BGP summary routes (Summary routes is the only option selected for the BGP neighbor), the Cato system service range and SDP user range are not advertised by default. You can manually configure the BGP neighbor to include these IP ranges as summary routes:

  • Default Cato system IP range: 10.254.254.0/24 (or custom system range) - primarily used for DNS

  • SDP user IP range: 10.41.0.0/16 (or custom SDP user range)

Edit_BGP_Summary_Route.png

To configure BGP Summary Routes for a BGP neighbor:

  1. From the navigation menu, click Network > Sites and select the site.

  2. From the navigation menu, click Site Settings > BGP.

  3. Click New to create a new BGP peer or edit an existing one. The Edit BGP Neighbor panel opens.

  4. In the Policy section, select Summary routes. The Summary Route table opens.

    Note: We recommend that you do not select both All routes or Summary routes. Selecting both options will advertise both the configured summary routes and all the unique routes over the network. This will cause BGP to advertise excessive number of routes and reduce the efficiency of summary routes.

  5. Click New and add BGP Summary Routes in CIDR notation.

    1. (Optional) Click the Add_Icon_CMA.png icon and Add to define BGP communities for a summary route. BGP communities have to be in a format of ASN:community 1-65535:1-65535. For more information, see Cato Reserved BGP Communities.

  6. Click Apply, and then click Save.

Monitoring BGP Summary Routes

You can monitor and verify the status of your BGP Summary Routes with any of the following options:

  • Show BGP Status - You can select this option in Site Configuration > BGP to show the status of BGP for your site and its current advertisements over the network.

  • Cato Management Applications Events - Inspect BGP related events. You can see the different types of BGP events in Defining BGP Neighbors.

  • Routing Table - All routes, including dynamic summary routes, are visible in the Routing Table. The routing table includes information on summary route IPs such as the source site, last route update, AS path and more.

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3 comments

  • Comment author
    Gerwin Brocker

    Please add the limitations as mentioned in the Partner Tech Update.

  • Comment author
    Yaakov Simon

    Gerwin Brocker excellent suggestion! We updated the article with these limits, you can configure up to:

    • 64 summary routes per BGP peer

    • 5 communities per summary route

  • Comment author
    Yaakov Simon
    • Edited

    Updated article to include support for IPsec and Cross Connect sites, and for Socket v19.0 and higher

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