Azure and Cisco Router not forming an express route BGP session

Hello @Gunther Fembini ,

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

I understand that you've set up an Azure ExpressRoute connection with private peering but BGP between Azure and Cisco router is not UP. As mentioned in the below Azure ExpressRoute troubleshooting doc,

If the state of an eBGP peering between an MSEE and a CE/PE-MSEE is Active or Idle, check if the assigned primary and secondary peer subnets match the configuration on the linked CE/PE-MSEE. Also check if the correct VlanId, AzureASN, and PeerASN values are used on MSEEs, and if these values map to the ones used on the linked CE/PE-MSEE. If MD5 hashing is chosen, the shared key should be the same on MSEE and CE/PE-MSEE pairs. If you need to change any of these configurations on an MSEE router, see Create and modify routing for an ExpressRoute circuit.

Refer: https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-troubleshooting-expressroute-overview#validate-bgp-and-routes-on-the-msee

Did you validate all your configuration?

On the Cisco router, what is the result of show ip bgp summary?

If the BGP state shows idle, then we may need to drill into the logs to find why the BGP peering is down between MSEE and CE.

Could you please also check the below details:

• Is BFP (Bidirectional Forwarding Detection) configured properly?

Refer: https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-bfd#enabling-bfd

• Are the Cisco interfaces configured properly to use eBGP and advertise routes to Microsoft?

Refer: https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-config-samples-routing#cisco-ios-xe-based-routers

• Do you have shared key/MD5 hashing configured? If yes, the shared key should be the same on MSEE and CE/PE-MSEE pairs.

NOTE: The limit is a maximum of 25 alphanumeric characters. Special characters aren't supported.

Refer: https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-howto-routing-portal-resource-manager#private

• I've also seen instances where customer configured BGP with the same ASN in local and remote BGP peers. From the customer configuration, the remote peer ASN must be Azure's 12076 ASN. Please validate the ASN configuration again.

Regards,

Gita

@Gunther Fembini , could you please provide an update on this post?

Still no change. I get no messaging from the Azure side that it is even trying to form a BGP neighborship with my Cisco router. Cisco is trying to form a relationship meanwhile Azure is not even trying.

@Gunther Fembini , is the ARP (Address Resolution Protocol) UP?

Refer: https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-troubleshooting-expressroute-overview#validate-arp

https://video2.skills-academy.com/en-us/azure/expressroute/expressroute-troubleshooting-arp-resource-manager

If yes, could you please share what is the result of show ip bgp summary on the Cisco router?