0

I have 2 vnets (same subscription), one in AU (10.2.0.0/18) and one in UK (10.2.64.0/18). The vnets are connected together and virtual PCs connected to each vnet can ping each other.

Click here for topology

My AU vnet is also connected to my on-premises router via an ExpressRoute circuit and I can ping a virtual PC in my AU vnet from my on-premises network, and the routing table of my on-premises router connected to ExpressRoute shows a route to my AU vnet via ExpressRoute.

However, my on-premises router isn't learning the route to the UK vnet at all. I'm expecting it to learn the route to the UK vnet via the AU vnet. And the UK vnet doesnt appear to be learning any routes avertised by my on-premises router.

Now the interesting part is that if I create a static route on my on-premises router to the UK vnet via my ExpressRoute circuit and try to ping or traceroute to the UK vnet the router on the Azure-end of the ExpressRoute circuit just sends 'Unreachable' replies to the pings or traceroutes. So it seems as tho the ExpressRoute circuit maintains a different routing table to the connected vnet and routes arent distributed between the routing tables.

Anyone know how to have the routes advertised by the UK vnet advertised to my on-premises router, and the routes from my on-premises router advertised to my UK vnet?

1

Use Vnet peering between AU and UK Vnets, which would ultimately help you in route advertising in both the ways and the communication between your Vnets would remain same.

https://docs.microsoft.com/en-us/azure/vpn-gateway/vpn-gateway-peering-gateway-transit

Note: Please delete the Vnet gateway in UK Vnet to use Transit routing via Vnet peering.

0

my on-premises router isn't learning the route to the UK vnet at all.

This is a by design behavior, we can't use ExpressRoute in this way. Because azure not have a route entry to route an outside IP to another Vnet. (For now, Azure can't route outside traffic to another Vnet)

Anyone know how to have the routes advertised by the UK vnet advertised to my on-premises router, and the routes from my on-premises router advertised to my UK vnet?

We can set up a side-to-site VPN between on-prem and UK vnet.

3
  • Please let me know if you would like further assistance.
    – Jason Ye
    Mar 17 '17 at 6:53
  • Thanks Jason but that contradicts what I was told by Microsoft before we signed up to Azure. So is it not possible at all to have our AU on-prem router and our UK on-prem router connect to Azure via ExpressRoute, and then use Azure to bridge the connection between the two ExpressRoute circuits? Mar 19 '17 at 23:40
  • @EvilSibling Vnets not in the same geopolitical region,so we can 't link Vnets to an expressroute circuit. In your scenario, I recommend you to deploy S2S vpn between UK and on-prem.
    – Jason Ye
    Mar 20 '17 at 8:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.