How to tweak the BGP Table of an Azure EXpressroute for one external IP address?

Question

question

DiederikJanson-0956 asked Apr 29, '22 DiederikJanson-0956 answered May 27, '22

How to tweak the BGP Table of an Azure EXpressroute for one external IP address?

Hi,

Several vnets we have in Azure are routed through our Expressroute back to our internal network. This works great.

For one vnet (Our Azure Virtual Desktop vnet) we made a udr (route table) of 0.0.0.0/0 with next hop internet.

Now I would like one external ip address not to go via the internet next hop but via the expressroute back to our internal network and then via our own external ip to the internet (this because of ip white listing on the destination). Because the traffice needs to go to an Expressroute circuit this needs to be done with bgp.

I have no idea how, can't find it in the documentation and i don't know if this is possible at all?

Any ideas?

Best Regards.

DJITS

azure-expressroute

5 |1600 characters needed characters left characters exceeded

Attachments: Up to 10 attachments (including images) can be used with a maximum of 3.0 MiB each and 30.0 MiB total.

Answer 1 · 2022-05-02T03:39:19.07Z

AhmedMuhi-8046 answered May 2, '22 AhmedMuhi-8046 commented May 17, '22

Hey DJITS,

So my understanding of your setup is this:

1- You have a VNet that is the Azure Virtual Desktop VNet, with an Expressroute connection back to on-premises (Internal network).
2- You have a UDR on that VNet with a default route 0.0.0.0 next-hop Internet.
3- For one specific destination on the Internet you need traffic to be sent toward your On-Premises instead of directly toward the Internet, right?

Could you try to create a UDR on the VNet with a next-hop of an IP address of your Internal Router/Firewall that is connected to the Internet, and since your VNet learned this route through the ExpressRoute BGP, it would use the ExpressRoute back to your On-premises.

Let me know how it goes.

All the best, and Stay strong!

Cheers,
Ahmed Muhi

· 2

5 |1600 characters needed characters left characters exceeded

Attachments: Up to 10 attachments (including images) can be used with a maximum of 3.0 MiB each and 30.0 MiB total.

DiederikJanson-0956 · May 13 at 11:34 AM

Hi Ahmed,

Our network partner was able to add the ip address to the bgp route table on our site. This works.

Thanx for helping.

Best Regards,

DJITS.

0 ·

AhmedMuhi-8046 · May 16 at 07:38 PM

Hey DJITS,

I am glad that helped :)

All the best!

Cheers,
Ahmed Muhi

0 ·

Answer 2 · 2022-05-27T17:36:29.827Z

DiederikJanson-0956 answered May 27, '22

Hi Ahmed,

Our network partner managed to add the ip address to our internal bgp table and that worked.

Thanx for your thoughts.

Cheers,

DJITS.

5 |1600 characters needed characters left characters exceeded

Attachments: Up to 10 attachments (including images) can be used with a maximum of 3.0 MiB each and 30.0 MiB total.

question