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ExpressRoute routing requirements

  • Grein

To connect to Microsoft cloud services using ExpressRoute, you need to set up and manage routing. Some connectivity providers offer setting up and managing routing as a managed service. Check with your connectivity provider to see if they offer this service. If they don't, you must adhere to the following requirements:

Refer to the Circuits and routing domains article for a description of the routing sessions that need to be set up in to facilitate connectivity.

Note

Microsoft doesn't support any router redundancy protocols such as HSRP or VRRP for high availability configurations. We rely on a redundant pair of BGP sessions per peering for high availability.

IP addresses used for peering

You need to reserve a few blocks of IP addresses to configure routing between your network and Microsoft's Enterprise edge (MSEEs) routers. This section provides a list of requirements and describes the rules regarding how these IP addresses must be acquired and used.

IP addresses used for Azure private peering

You can use either private IP addresses or public IP addresses to configure the peering. The address range used for configuring routes can't overlap with address ranges used for virtual networks in Azure.

  • IPv4:
    • You must reserve a /29 subnet or two /30 subnets for routing interfaces.
    • The subnets used for routing can be either private IP addresses or public IP addresses.
    • The subnets must not conflict with the range reserved by the customer for use in the Microsoft cloud.
    • If a /29 subnet is used, it's split into two /30 subnets.
      • The first /30 subnet is used for the primary link and the second /30 subnet is used for the secondary link.
      • For each of the /30 subnets, you must use the first IP address of the /30 subnet for your router. Microsoft uses the second IP address of the /30 subnet to set up a BGP session.
      • You must set up both BGP sessions for the availability SLA to be valid.
  • IPv6:
    • You must reserve a /125 subnet or two /126 subnets for routing interfaces.
    • The subnets used for routing can be either private IP addresses or public IP addresses.
    • The subnets must not conflict with the range reserved by the customer for use in the Microsoft cloud.
    • If a /125 subnet is used, it's split into two /126 subnets.
      • The first /126 subnet is used for the primary link and the second /126 subnet is used for the secondary link.
      • For each of the /126 subnets, you must use the first IP address of the /126 subnet for your router. Microsoft uses the second IP address of the /126 subnet to set up a BGP session.
      • You must set up both BGP sessions for the availability SLA to be valid.

Example for private peering

If you choose to use a.b.c.d/29 to set up the peering, it's split into two /30 subnets. In the following example, notice how the a.b.c.d/29 subnet is used:

  • a.b.c.d/29 is split to a.b.c.d/30 and a.b.c.d+4/30 and passed down to Microsoft through the provisioning APIs.
    • You use a.b.c.d+1 as the VRF IP for the Primary PE and Microsoft uses a.b.c.d+2 as the VRF IP for the primary MSEE.
    • You use a.b.c.d+5 as the VRF IP for the secondary PE and Microsoft uses a.b.c.d+6 as the VRF IP for the secondary MSEE.

Consider a case where you select 192.168.100.128/29 to set up private peering. 192.168.100.128/29 includes addresses from 192.168.100.128 to 192.168.100.135, among which:

  • 192.168.100.128/30 is assigned to link1, with provider using 192.168.100.129 and Microsoft using 192.168.100.130.
  • 192.168.100.132/30 is assigned to link2, with provider using 192.168.100.133 and Microsoft using 192.168.100.134.

IP addresses used for Microsoft peering

You must use public IP addresses that you own for setting up the BGP sessions. Microsoft must be able to verify the ownership of the IP addresses through Routing Internet Registries and Internet Routing Registries.

  • The IPs listed in the portal for Advertised Public Prefixes for Microsoft Peering creates ACLs for the Microsoft core routers to allow inbound traffic from these IPs.
  • You must use a unique /29 (IPv4) or /125 (IPv6) subnet or two /30 (IPv4) or /126 (IPv6) subnets to set up the BGP peering for each peering per ExpressRoute circuit, if you have more than one.
  • If a /29 subnet is used, it's split into two /30 subnets.
  • The first /30 subnet is used for the primary link and the second /30 subnet is used for the secondary link.
  • For each of the /30 subnets, you must use the first IP address of the /30 subnet on your router. Microsoft uses the second IP address of the /30 subnet to set up a BGP session.
  • If a /125 subnet is used, it's split into two /126 subnets.
  • The first /126 subnet is used for the primary link and the second /126 subnet is used for the secondary link.
  • For each of the /126 subnets, you must use the first IP address of the /126 subnet on your router. Microsoft uses the second IP address of the /126 subnet to set up a BGP session.
  • You must set up both BGP sessions for our availability SLA to be valid.

Public IP address requirement

Private peering

You can choose to use public or private IPv4 addresses for private peering. We provide end-to-end isolation of your traffic, so overlapping of addresses with other customers isn't possible for private peering. These addresses aren't advertised to Internet.

Microsoft peering

The Microsoft peering path lets you connect to Microsoft cloud services. The list of services includes Microsoft 365 services, such as Exchange Online, SharePoint Online, Skype for Business, and Microsoft Teams. Microsoft supports bi-directional connectivity on the Microsoft peering. Traffic destined to Microsoft cloud services must use valid public IPv4 addresses before they enter the Microsoft network.

Make sure that your IP address and AS number are registered to you in one of the following registries:

If your prefixes and AS number aren't assigned to you in the preceding registries, you need to open a support case for manual validation of your prefixes and ASN. Support requires documentation, such as a Letter of Authorization that proves you're allowed to use that prefix.

A Private AS Number is allowed with Microsoft Peering, but requires manual validation. In addition, we remove private AS numbers in the AS PATH for the received prefixes. As a result, you can't append private AS numbers in the AS PATH to influence routing for Microsoft Peering. Additionally, AS numbers 64496 - 64511 reserved by IANA for documentation purposes aren't allowed in the path.

Important

Do not advertise the same public IP route to the public Internet and over ExpressRoute. To reduce the risk of incorrect configuration causing asymmetric routing, we strongly recommend that the NAT IP addresses advertised to Microsoft over ExpressRoute be from a range that is not advertised to the internet at all. If this is not possible to achieve, it is essential to ensure you advertise a more specific range over ExpressRoute than the one on the Internet connection. Besides the public route for NAT, you can also advertise over ExpressRoute the Public IP addresses used by the servers in your on-premises network that communicate with Microsoft 365 endpoints within Microsoft.

Dynamic route exchange

Routing exchange is over eBGP protocol. EBGP sessions are established between the MSEEs and your routers. Authentication of BGP sessions isn't a requirement. If necessary, an MD5 hash can be configured. See the Configure routing and Circuit provisioning workflows and circuit states for information about configuring BGP sessions.

Autonomous System numbers (ASN)

Microsoft uses AS 12076 for Azure public, Azure private and Microsoft peering. We have reserved ASNs from 65515 to 65520 for internal use. Both 16 bit and 32-bit AS numbers are supported.

There are no requirements around data transfer symmetry. The forward and return paths may traverse different router pairs. Identical routes must be advertised from either sides across multiple circuit pairs belonging to you. Route metrics aren't required to be identical.

Route aggregation and prefix limits

ExpressRoute supports up to 4000 IPv4 prefixes and 100 IPv6 prefixes advertised to Microsoft through the Azure private peering. This limit can be increased up to 10,000 IPv4 prefixes if the ExpressRoute premium add-on is enabled. ExpressRoute accept up to 200 prefixes per BGP session for Azure public and Microsoft peering.

The BGP session is dropped if the number of prefixes exceeds the limit. ExpressRoute accept default routes on the private peering link only. Provider must filter out default route and private IP addresses (RFC 1918) from the Azure public and Microsoft peering paths.

Transit routing and cross-region routing

ExpressRoute can't be configured as transit routers. You have to rely on your connectivity provider for transit routing services.

Advertising default routes

Default routes are permitted only on Azure private peering sessions. In such a case, ExpressRoute routes all traffic from the associated virtual networks to your network. Advertising default routes into private peering results in the internet path from Azure being blocked. You must rely on your corporate edge to route traffic from and to the internet for services hosted in Azure.

Some services are not able to be accessed from your corporate edge. To enable connectivity to other Azure services and infrastructure services, you must use user-defined routing to allow internet connectivity for every subnet requiring Internet connectivity for these services.

Note

Advertising default routes will break Windows and other VM license activation. For information about a work around, see use user defined routes to enable KMS activation.

Support for BGP communities

This section provides an overview of how BGP communities get used with ExpressRoute. Microsoft advertises routes in the private, Microsoft and public (deprecated) peering paths with routes tagged with appropriate community values. The rationale for doing so and the details on community values are describe as followed. Microsoft, however, doesn't honor any community values tagged to routes advertised to Microsoft.

For private peering, if you configure a custom BGP community value on your Azure virtual networks, you'll see this custom value and a regional BGP community value on the Azure routes advertised to your on-premises over ExpressRoute.

Note

In order for Azure routes to show regional BGP community values, you first must configure the custom BGP community value for the virtual network.

For Microsoft peering, you're connecting to Microsoft through ExpressRoute at any one peering location within a geopolitical region. You also have access to all Microsoft cloud services across all regions within the geopolitical boundary.

For example, if you connected to Microsoft in Amsterdam through ExpressRoute, you have access to all Microsoft cloud services hosted in North Europe and West Europe.

Refer to the ExpressRoute partners and peering locations page for a detailed list of geopolitical regions, associated Azure regions, and corresponding ExpressRoute peering locations.

You can purchase more than one ExpressRoute circuit per geopolitical region. Having multiple connections offers you significant benefits on high availability due to geo-redundancy. In cases where you have multiple ExpressRoute circuits, you receive the same set of prefixes advertised from Microsoft on the Microsoft peering paths. This configuration results in multiple paths from your network into Microsoft. This set up can potentially cause suboptimal routing decisions to be made within your network. As a result, you may experience suboptimal connectivity experiences to different services. You can rely on the community values to make appropriate routing decisions to offer optimal routing to users.

Microsoft Azure region Regional BGP community (private peering) Regional BGP community (Microsoft peering) Storage BGP community SQL BGP community Azure Cosmos DB BGP community Backup BGP community
North America
East US 12076:50004 12076:51004 12076:52004 12076:53004 12076:54004 12076:55004
East US 2 12076:50005 12076:51005 12076:52005 12076:53005 12076:54005 12076:55005
West US 12076:50006 12076:51006 12076:52006 12076:53006 12076:54006 12076:55006
West US 2 12076:50026 12076:51026 12076:52026 12076:53026 12076:54026 12076:55026
West US 3 12076:50044 12076:51044 12076:52044 12076:53044 12076:54044 12076:55044
West Central US 12076:50027 12076:51027 12076:52027 12076:53027 12076:54027 12076:55027
North Central US 12076:50007 12076:51007 12076:52007 12076:53007 12076:54007 12076:55007
South Central US 12076:50008 12076:51008 12076:52008 12076:53008 12076:54008 12076:55008
Central US 12076:50009 12076:51009 12076:52009 12076:53009 12076:54009 12076:55009
Canada Central 12076:50020 12076:51020 12076:52020 12076:53020 12076:54020 12076:55020
Canada East 12076:50021 12076:51021 12076:52021 12076:53021 12076:54021 12076:55021
South America
Brazil South 12076:50014 12076:51014 12076:52014 12076:53014 12076:54014 12076:55014
Europe
North Europe 12076:50003 12076:51003 12076:52003 12076:53003 12076:54003 12076:55003
West Europe 12076:50002 12076:51002 12076:52002 12076:53002 12076:54002 12076:55002
UK South 12076:50024 12076:51024 12076:52024 12076:53024 12076:54024 12076:55024
UK West 12076:50025 12076:51025 12076:52025 12076:53025 12076:54025 12076:55025
France Central 12076:50030 12076:51030 12076:52030 12076:53030 12076:54030 12076:55030
France South 12076:50031 12076:51031 12076:52031 12076:53031 12076:54031 12076:55031
Switzerland North 12076:50038 12076:51038 12076:52038 12076:53038 12076:54038 12076:55038
Switzerland West 12076:50039 12076:51039 12076:52039 12076:53039 12076:54039 12076:55039
Germany North 12076:50040 12076:51040 12076:52040 12076:53040 12076:54040 12076:55040
Germany West Central 12076:50041 12076:51041 12076:52041 12076:53041 12076:54041 12076:55041
Norway East 12076:50042 12076:51042 12076:52042 12076:53042 12076:54042 12076:55042
Norway West 12076:50043 12076:51043 12076:52043 12076:53043 12076:54043 12076:55043
Asia Pacific
East Asia 12076:50010 12076:51010 12076:52010 12076:53010 12076:54010 12076:55010
Southeast Asia 12076:50011 12076:51011 12076:52011 12076:53011 12076:54011 12076:55011
Japan
Japan East 12076:50012 12076:51012 12076:52012 12076:53012 12076:54012 12076:55012
Japan West 12076:50013 12076:51013 12076:52013 12076:53013 12076:54013 12076:55013
Australia
Australia East 12076:50015 12076:51015 12076:52015 12076:53015 12076:54015 12076:55015
Australia Southeast 12076:50016 12076:51016 12076:52016 12076:53016 12076:54016 12076:55016
Australia Government
Australia Central 12076:50032 12076:51032 12076:52032 12076:53032 12076:54032 12076:55032
Australia Central 2 12076:50033 12076:51033 12076:52033 12076:53033 12076:54033 12076:55033
India
India South 12076:50019 12076:51019 12076:52019 12076:53019 12076:54019 12076:55019
India West 12076:50018 12076:51018 12076:52018 12076:53018 12076:54018 12076:55018
India Central 12076:50017 12076:51017 12076:52017 12076:53017 12076:54017 12076:55017
Korea
Korea South 12076:50028 12076:51028 12076:52028 12076:53028 12076:54028 12076:55028
Korea Central 12076:50029 12076:51029 12076:52029 12076:53029 12076:54029 12076:55029
South Africa
South Africa North 12076:50034 12076:51034 12076:52034 12076:53034 12076:54034 12076:55034
South Africa West 12076:50035 12076:51035 12076:52035 12076:53035 12076:54035 12076:55035
UAE
UAE North 12076:50036 12076:51036 12076:52036 12076:53036 12076:54036 12076:55036
UAE Central 12076:50037 12076:51037 12076:52037 12076:53037 12076:54037 12076:55037

All routes advertised from Microsoft are tagged with the appropriate community value.

Important

Global prefixes are tagged with an appropriate community value.

Service to BGP community value

In addition to the BGP tag for each region, Microsoft also tags prefixes based on the service they belong to. This tagging only applies to the Microsoft peering. The following table provides a mapping of service to BGP community value. You can run the 'Get-AzBgpServiceCommunity' cmdlet for a full list of the latest values.

Service BGP community value
Exchange Online (2) 12076:5010
SharePoint Online (2) 12076:5020
Skype For Business Online (2) and (3) 12076:5030
CRM Online (4) 12076:5040
Azure Global Services (1) 12076:5050
Microsoft Entra ID 12076:5060
Azure Resource Manager 12076:5070
Other Office 365 Online services (2) 12076:5100
Microsoft Defender for Identity 12076:5220
Microsoft PSTN services (5) 12076:5250

(1) Azure Global Services includes only Azure DevOps at this time.

(2) Authorization required from Microsoft. See Configure route filters for Microsoft Peering.

(3) This community also publishes the needed routes for Microsoft Teams services.

(4) CRM Online supports Dynamics v8.2 and below. For higher versions, select the regional community for your Dynamics deployments.

(5) Use of Microsoft Peering with PSTN services is restricted to specific use cases. See Using ExpressRoute for Microsoft PSTN services.

Note

Microsoft does not honor any BGP community values that you set on the routes advertised to Microsoft.

BGP Community support in National Clouds

National Clouds Azure Region BGP community value
US Government
US Gov Arizona 12076:51106
US Gov Iowa 12076:51109
US Gov Virginia 12076:51105
US Gov Texas 12076:51108
US DoD Central 12076:51209
US DoD East 12076:51205
China
China North 12076:51301
China East 12076:51302
China East 2 12076:51303
China North 2 12076:51304
China North 3 12076:51305
Service in National Clouds BGP community value
US Government
Exchange Online 12076:5110
SharePoint Online 12076:5120
Skype For Business Online 12076:5130
Microsoft Entra ID 12076:5160
Other Office 365 Online services 12076:5200
  • Office 365 communities aren't supported over Microsoft Peering for Microsoft Azure operated by 21Vianet region.

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