er-ms-peering-bgp-community

ExpressRoute Microsoft peering: how to retrieve the list of prefixes associated with BGP community

Simple powershell script to get the list of prefixes in ExpressRoute Microsoft peering with specific BGP community.

Office 365 IP prefixes that are advertised over ExpressRoute Microsoft peering are tagged with service specific BGP community values:

Service	BGP Community Value
Exchange	12076:5010
sharepoint	12076:5020
skype for business	12076:5030
other Office 365 services	12076:5100

To run the script you need to login in your Azure subscription by Login-AzAccount To select all the prefixes associated with a specific BGP community, i.e. Skype for business:

Get-AzBgpServiceCommunity | ? {$_.name -eq 'SkypeForBusiness' }

Get-AzBgpServiceCommunity | ?{$_.Name -eq 'Exchange' -or $_.Name -eq 'Sharepoint' -or $_.Name -eq 'SkypeForBusiness' -or $_.Name -eq 'OtherOffice365Services'}

Powershell script to extract BGP communities names and BGP community value:

$fullList=Get-AzBgpServiceCommunity 
$BGPCommunityName=@()
$BGPCommunity=@{}

# use the hash table to store (BGP community name, BGP community value)
foreach ($i in $fullList)
{
  $BGPCommunity.Add($i.Name,$i.BgpCommunities.CommunityValue)
} 
$BGPCommunity

foreach ($i in $fullList)
{
  $BGPCommunityName +=$i.Name
} 
Write-Host ''
Write-Host 'full list of BGP community name:'
Write-Host -Separator "`n" $BGPCommunityName -ForegroundColor Cyan

# $str: substring to search
# search all the BGP communities name for SQL
$str= "SQL"
foreach ($i in $BGPCommunityName )
{
  $s=$str.toLower()
 if ($i.toLower().Contains($s)) { 
   Write-Host $i -ForegroundColor Yellow
 }
}