Hello, New Express routes from Dataceter1 & Datacenter2. Service provider will hand over 2 physical cables for redundancy. ERs will be used for both private and Microsoft peering. What is the recommended approach for BGP peering? A) Say DC1- Use both links to form BGP private peering (via subinterfaces/Vlan ID) and then use same physical links to form Microsoft peering (new subinterfaces/VlanID) when needed? This works? Same with DC2 ER. B) DC1: One physical link subinterface > private peering and other physical link sub interface for Microsoft peering? Same with DC2. Schema attached. Thanks in advance.

@msheik24 , Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well. I understand that you would like to know about the redundancy configuration for ExpressRoute. For ExpressRoute SLA to be valid, you must have two connections (for Both MS and Private Peering). And as such, you must use the design A. Because, if you were to use design B, and if one Physical connection goes down - you will lose an entire Peering (either MS or Private). However, with design A, you will still have one Physical connection that provides both MS and Private Peering. See : ExpressRoute routing requirements You must set up both BGP sessions for the availability SLA to be valid. Thanks, Kapil Please Accept an answer if correct. Original posters help the community find answers faster by identifying the correct answer.

Express Route - Private and Microsoft peering

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KapilAnanth-MSFT 46,776 Reputation points Microsoft Employee

2024-02-26T04:16:42.03+00:00
@msheik24 ,

Welcome to the Microsoft Q&A Platform. Thank you for reaching out & I hope you are doing well.

I understand that you would like to know about the redundancy configuration for ExpressRoute. For ExpressRoute SLA to be valid, you must have two connections (for Both MS and Private Peering).

And as such, you must use the design A.

Because, if you were to use design B, and if one Physical connection goes down - you will lose an entire Peering (either MS or Private).

However, with design A, you will still have one Physical connection that provides both MS and Private Peering.

See : ExpressRoute routing requirements

You must set up both BGP sessions for the availability SLA to be valid.

Thanks,

Kapil

Please Accept an answer if correct.

Original posters help the community find answers faster by identifying the correct answer.
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msheik24 20 Reputation points

2024-02-26T23:42:43.3166667+00:00

Hi Kapil, Thank you for your suggestion. Each DC has one ER from different provider via different paths (one thru NY and another thru DC). Both DC users hit same VNET/public services and I'll use route-maps to manipulate advertisement so it will be redundant. Based on below diagram, recommendation seems like establishing one private and one public peer from DC1 (as ER comes with 2 physical links - one sub interface for private and another for Public) and same from DC2. Can you please clarify on this? Thank you,

KapilAnanth-MSFT 46,776 Reputation points Microsoft Employee

2024-02-27T05:57:52.2866667+00:00

@msheik24 ,

Thanks for sharing your architecture.

When you have 2 ExpressRoute Circuits, from 2 different Service Providers,

The choice is really up to you.

A single Physical Connection can have maximum of 2 Peerings (MS and Private)

As I mentioned earlier, a single ExpressRoute Circuit from a Service Provider is capable of providing 2 Physical Connections. (from ISP end to Azure end)

The above is recommended and used in majority of the cases.

This uses 2 Peerings per Physical connection - so totally 4 Peerings.

And if one Physical Connection fails, you still have 2 Peerings (one MS and one Private)

In your scenario,

When you have 2 ExpressRoute Circuits from 2 Service Providers, basically you have 4 Physical Connections. (2 through NY and 2 through DC)

This means, you can use 1 Peering per Physical connection - again, totally 4 Peerings like above.

The difference is that if one Physical Connection fails (say the one with MS Peering), you will have 3 Peerings left (one MS and two Private)

In both the cases, you have redundant connectivity and traffic should flow despite a single Physical Connection failing.

Thanks,

Kapil

Please don’t forget to close the thread by clicking "Accept the answer" wherever the information provided helps you, as this can be beneficial to other community members.

msheik24 20 Reputation points

2024-02-27T19:56:07.6133333+00:00

Hi Kapil, great info. Thanks for all your time and details. based on your insight and info from community, DC1- ER: primary L2 physical connection will have 2peerings (Private, public) via subinterfaces and use for production related traffic.. Secondary L2 physical connection will also have 2 peerings but recommended to use for non-prod/test related activity so that the bandwidth is available as backup. Same goes with DC2. In total 8 peering with 4 active and rest for non-critical/light traffic. Thanks again for all your help.

KapilAnanth-MSFT 46,776 Reputation points Microsoft Employee

2024-02-28T02:57:03.31+00:00

@msheik24 , Glad we could be of assistance. Thanks for your continued contribution on Q&A and appreciate much for taking the time to share your feedback. Cheers, Kapil
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