Introduction to BGP Routing on Windows Server 2019

Border Gateway Protocol (BGP) is the routing protocol that powers the internet, used to exchange routing information between autonomous systems (AS). In Windows Server 2019, BGP routing is available as part of the Remote Access role and is commonly used in software-defined networking scenarios, branch office connectivity, and hybrid cloud deployments where Windows Server acts as a virtual BGP router. Microsoft Azure also supports BGP for ExpressRoute and VPN Gateway connections, making Windows Server BGP valuable for hybrid connectivity scenarios.

Windows Server 2019 BGP supports iBGP (internal BGP between routers in the same AS) and eBGP (external BGP between different autonomous systems). It supports route policies including prefix lists, AS path filters, community attributes, and multi-exit discriminator (MED) values.

Installing the Remote Access Role for BGP

BGP in Windows Server 2019 requires the Remote Access role with the Routing sub-feature:

Install-WindowsFeature -Name RemoteAccess, Routing -IncludeManagementTools

Enable IP routing by configuring RRAS:

Install-RemoteAccess -VpnType RoutingOnly

Alternatively, if you only need routing (not VPN), enable just the routing component:

Set-ItemProperty -Path "HKLM:SYSTEMCurrentControlSetServicesTcpipParameters" -Name "IPEnableRouter" -Value 1
Restart-Service -Name RemoteAccess

Configuring a BGP Router

Create a BGP router instance. You must specify an AS (Autonomous System) number — use a private AS number (64512-65534) for internal routing:

Add-BgpRouter -BgpIdentifier 192.168.1.10 -LocalASN 65001

The BGP identifier is typically the highest loopback or management IP of the router. Verify the BGP router was created:

Get-BgpRouter

Adding BGP Peers

Add an eBGP peer (a router in a different autonomous system). For example, peering with an upstream ISP router:

Add-BgpPeer -Name "ISP-Peer" -LocalIPAddress 203.0.113.1 -PeerIPAddress 203.0.113.2 -PeerASN 65000 -LocalASN 65001 -PeeringMode Automatic -HoldTimeSec 30 -IdleHoldTimeSec 3

Add an iBGP peer (a router in the same autonomous system):

Add-BgpPeer -Name "Internal-Router" -LocalIPAddress 192.168.1.10 -PeerIPAddress 192.168.1.20 -PeerASN 65001 -LocalASN 65001 -PeeringMode Automatic

View all configured BGP peers and their state:

Get-BgpPeer | Select PeerName, PeerIPAddress, PeerASN, BgpState, ConnectedSince

A peer in the “Established” state is actively exchanging routing information.

Advertising Routes via BGP

Advertise (inject) local routes into BGP so peers learn about your networks. Add a network to BGP routing:

Add-BgpNetwork -Network "192.168.1.0/24" -InterfaceAlias "Ethernet 1"

Advertise multiple networks:

Add-BgpNetwork -Network "10.0.0.0/8" -InterfaceAlias "Internal NIC"
Add-BgpNetwork -Network "172.16.0.0/12" -InterfaceAlias "Internal NIC"

View currently advertised networks:

Get-BgpNetwork

Configuring BGP Route Policies

BGP route policies control which routes are accepted from peers and which routes are advertised. Create a route policy that allows only specific prefixes from a peer (prefix list filtering):

# Create a route policy that allows only the 10.0.0.0/8 prefix
Add-BgpRouteAggregate -Prefix "10.0.0.0/8" -PreserveASPath Enabled -SummaryOnly Disabled

Set AS path prepending to make routes less preferred by adding your AS to the path multiple times:

Set-BgpPeer -Name "ISP-Peer" -RoutingDomain "Default" -MaxAllowedPrefix 100

Viewing BGP Routing Table

View all BGP-learned routes in the routing table:

Get-BgpRouteInformation | Select Network, NextHop, Origin, LocalPref, Med, AsPath

Filter for routes learned from a specific peer:

Get-BgpRouteInformation -PeerList "ISP-Peer" | Select Network, NextHop, AsPath

View routes being advertised to a peer:

Get-BgpStatistics | Select PeerName, TotalNetworkRoutesAdvertised, TotalNetworkRoutesLearned

Troubleshooting BGP

Check BGP session statistics for a peer:

Get-BgpStatistics -PeerName "ISP-Peer"

Force a BGP session to reset (useful after configuration changes):

Clear-BgpSession -PeerName "ISP-Peer" -Force

Enable BGP logging to see detailed session events:

Get-WinEvent -LogName "Microsoft-Windows-RRAS/Operational" | Where-Object {$_.Message -like "*BGP*"} | Select TimeCreated, Message | Select-Object -First 20

Windows Server 2019 BGP is a capable software routing solution well-suited for small and medium-scale deployments, lab environments, and Microsoft Azure gateway appliances where a full-featured hardware router is not justifiable.