What is the maximum amount of routes the Azure Route Server can advertise to a BGP peer in the outbound direction?

Question

The Microsoft public documentation explains that the Azure Route Server is able to receive a maximum of 1000 prefixes inbound from a BGP peer, with a maximum of 8 unique BGP peers established.
What is the maximum amount of routes the Route Server can advertise in the outbound direction to a single established BGP peer? This is not currently documented from what I can tell.

https://learn.microsoft.com/en-us/azure/route-server/route-server-faq#route-server-limits

Answer 1

Hello @Charlie O'Riordan

Thank you for your heads up.

You are right that on that specific document is not stating the accurate value but I was reading in deep about this because you can peer toward another Router Server or NVA(Network virtual appliance) but that depends on if it is over an IPsec VPN or ER(ExpressRoute) or UDR BGP propagation.

Having said that check this note below:

So based on the next chart below, we could get an idea that peering can be made using IPsec VPN or ER circuit for BGP peering which ends up demonstrating that the answer is 200.

Furthermore, you can use Hub-and-Spoke topology but on the Hub segment can be use an NVA since Route server can not support transit routing/Forwarding data.

If an NVA advertises more than what the Route server can support, well this provoke BGP peering flapping issues and dropping the remaining routes that are out of the scope.

Besides that, by using UDR tables I found that there is a limitation of routes can not be more than 400 routes as shown below as well.

Finally, Route server using BGP is a open source or Route server uses a dedicated daemon to handle BGP protocol as dynamic routing protocol. You can refer yourself to the following link >>> https://www.quagga.net/

I hope this can help ya in some way since I had to invest enough time to get to the observation given above : )

Looking forward to your feedback,

Best Regards,

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Answer 2

Hello @Charlie O'Riordan

I hope you are doing excellent.

I am wondering if my previous answer was useful for you to get a better understanding of this.

Looking forward to your feedback,

Regards,

Please "Accept the answer" if the information helped you. This will help us and others in the community as well.