how to fix BGP down

Singh, Harvinder 0

how to fix BGP down, I can ping azure IP from my on Prem router. icmp is fine but tcp ping to port 179 is not fine, its dropped. I did some packet capture on router, I cannot see SYN-ACK received from Azure express route. so if tcp handshake is not complete then BGP will remain down. There is no firewall between on-prem router to azure.

Please help how to fix it.

Silvia Wibowo 3,411 Reputation points Microsoft Employee

2024-04-04T00:43:32.96+00:00
Hi @Singh, Harvinder , I understand that you have Express Route set up between Azure and on-premises, but having problem with BGP routing.

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.

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.

More info: IP addresses used for Azure private peering.
KapilAnanth-MSFT 39,211 Reputation points Microsoft Employee

2024-04-04T05:50:31.2866667+00:00
@Singh, Harvinder ,

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

I understand that you are experiencing that the BGP is down in your ExpressRoute.

I see you are not able to TCPPing Azure ExpressRoute Router (MSEE) over port 179.

This is not a correct validation mechanism.

May I know if this is a new set up?

If so, Can you validate the Circuit status and Provider status as Enabled and Provisioned respectively?

If yes, the make sure ARP is up first : Validate ARP

And check the Metric : ARP Availability - Split by Peering

If the ARP is up, follow the below for BGP validation.

Or this was an existing set up and the BGP is suddenly down?

Make sure ARP is up first : Validate ARP

And check the Metric : ARP Availability - Split by Peering

In this case, can you specify how you are confirming that the BGP is down.

From Azure end, can you Validate BGP and routes on the MSEE using the commands in the doc?

And check the Metric : BGP Availability - Split by Peer

Please share the results of the ARP, BGP Metrics and commands

Cheers,

Kapil
Singh, Harvinder 0 Reputation points

2024-04-04T19:34:15.7066667+00:00

BGP came up right away after configuring password/MD5. I was wondering its must condition here rather than optional. Anyways it worked.

telnet to port 179 still does not work, Microsoft might have blocked. but BGP is up now
KapilAnanth-MSFT 39,211 Reputation points Microsoft Employee

2024-04-05T06:13:08.4366667+00:00

@Singh, Harvinder ,

I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this!

Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others", I shall request you to please "Accept" the answer summarized by Silvia Wibowo .

Kindly let us know if this helps or you need further assistance on this issue.

Thanks,

Kapil

1 answer

Silvia Wibowo 3,411 Reputation points Microsoft Employee

2024-04-05T01:10:05.42+00:00

Hi @Singh, Harvinder , thank you for your update. Let me summarize your issue and solution.

Issue: Express Route set up between Azure and on-premises, but having problem with BGP remains down.

Solution: BGP came up right away after configuring password/MD5.

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