Hi Gabriel, In the first situation, it is most likely that Router A didn't have a default route to share. Using just the first situation, if you create a static default route, and then redistribute that into BGP, then the default-information originate should share the default route with Router B.
ExpressRoute routing requirements. 12 minutes to read.In this articleTo connect to Microsoft cloud services using ExpressRoute, you’ll 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 article for a description of the routing sessions that need to be set up in to facilitate connectivity. NoteMicrosoft does not support any router redundancy protocols (for example, HSRP, VRRP) for high availability configurations.
We rely on a redundant pair of BGP sessions per peering for high availability. IP addresses used for peeringsYou 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 peeringYou can use either private IP addresses or public IP addresses to configure the peerings. NoteAzure public peering is not avialable for new circuits.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.
You must use a unique /29 subnet or two /30 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 is 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. You must set up both BGP sessions for our to be valid.Public IP address requirement Private peeringYou 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 is not possible in case of private peering. These addresses are not advertised to Internet. Microsoft peeringThe Microsoft peering path lets you connect to Microsoft cloud services. The list of services includes Office 365 services, such as Exchange Online, SharePoint Online, Skype for Business, Microsoft Teams and Dynamics 365. 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 are not 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 are allowed to use the resources.A Private AS Number is allowed with Microsoft Peering, but will also require 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. ImportantDo 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 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 Office 365 endpoints within Microsoft. Public peering (deprecated - not available for new circuits)The Azure public peering path enables you to connect to all services hosted in Azure over their public IP addresses.
These include services listed in the and any services hosted by ISVs on Microsoft Azure. Connectivity to Microsoft Azure services on public peering is always initiated from your network into the Microsoft network.
You must use Public IP addresses for the traffic destined to Microsoft network. ImportantAll Azure PaaS services are accessible through Microsoft peering.A Private AS Number is allowed with public peering. Dynamic route exchangeRouting exchange will be over eBGP protocol. EBGP sessions are established between the MSEEs and your routers. Authentication of BGP sessions is not a requirement.
If required, an MD5 hash can be configured. See the and for information about configuring BGP sessions. Autonomous System numbersMicrosoft uses AS 12076 for Azure public, Azure private and Microsoft peering.
We have reserved ASNs from 65515 to 65520 for internal use. Both 16 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 are not required to be identical. Route aggregation and prefix limitsWe support up to 4000 prefixes advertised to us through the Azure private peering. This can be increased up to 10,000 prefixes if the ExpressRoute premium add-on is enabled. We 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.
We will 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 routingExpressRoute cannot be configured as transit routers.
You will have to rely on your connectivity provider for transit routing services. Advertising default routesDefault routes are permitted only on Azure private peering sessions. In such a case, we will route all traffic from the associated virtual networks to your network. Advertising default routes into private peering will result 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.To enable connectivity to other Azure services and infrastructure services, you must make sure one of the following items is in place:. Azure public peering is enabled to route traffic to public endpoints.
You use user-defined routing to allow internet connectivity for every subnet requiring Internet connectivity. NoteAdvertising default routes will break Windows and other VM license activation. Follow instructions to work around this. Support for BGP communitiesThis section provides an overview of how BGP communities will be used with ExpressRoute.
Microsoft will advertise routes in the public and Microsoft peering paths with routes tagged with appropriate community values. The rationale for doing so and the details on community values are described below. ImportantGlobal prefixes are tagged with an appropriate community value. Service to BGP community valueIn addition to the above, Microsoft will also tag prefixes based on the service they belong to. This applies only to the Microsoft peering.
The table below provides a mapping of service to BGP community value. You can run the 'Get-AzBgpServiceCommunity' cmdlet for a full list of the latest values. ServiceBGP community valueExchange OnlineSharePoint OnlineSkype For Business OnlineDynamics 365Azure Global Services.Other Office 365 Online services.Azure Global Services includes only Azure DevOps at this time. NoteMicrosoft 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 RegionBGP community valueUS GovernmentUS Gov Arizona6US Gov Iowa9US Gov Virginia5US Gov Texas8US DoD Central9US DoD East5Service in National CloudsBGP community valueUS GovernmentExchange OnlineSharePoint OnlineSkype For Business OnlineDynamics 365Other Office 365 Online servicesNext steps.Configure your ExpressRoute connection.