Transitioning to Expressroute from Meraki MX SiteToSite Routing question

Understood.

So If I set the existing route tables to next hop = none they will be ignored correct? I would like to leave them there just in case we need to switch back to Meraki for site to site but want them ignored by BGP-Express Route Gateway.

Will setting them to none be adequate for this or do I need to delete them completely?

On a side note I have another question

We had attempted to configure Expressroute this past weekend and we got to a point where not all VNETS were being advertised back to on prem. The only VNET being advertised back from MS was the VNET that the ER Gateway is on.

All VNETS are currently peered but there is a setting that was not set that I believe caused the other VNETS to not advertise back from Microsoft to on prem.

The following (see below) was not checked on any of the spoke VNETS.

It seems that if I enable this the spoke VNETS will advertise their routes back to us on prem through the Gateway.

Can you verify that this is the reason that they were not advertising back to us?

Again the only VNET advertised our side was the VNET that the GatewaySubnet is on.

Thanks in advance

@azure-000

Thank you for getting back.

Will setting them to none be adequate for this or do I need to delete them completely?

Azure selects a route based on the destination IP address, using the longest prefix match algorithm.

If multiple routes contain the same address prefix, Azure selects the route type, based on the following priority:

1. User-defined route
2. BGP route
3. System route

This is currently documented here. Setting the next hop to none will be adequate when it is less specific then the BGP route. If both the routes contain the same address, then UDR will take preference and traffic will be sent to none.

Can you verify that this is the reason that they were not advertising back to us?

Yes, your understanding is correct this option needs to enabled and will most likely fix the issue.More details regarding this option can be found here

I understand you have asked a new question for this issue here

https://video2.skills-academy.com/en-us/answers/questions/1693731/expressroute-bgp-advertising-issue

I will make this comment there as well and lets continue our discussion there if this does not fix the issue.

Please let me know if you have any additional questions. Thank you!

Please "Accept the answer" if the information helped you. This will help us and others in the community as well.

Thanks for the information. So if I have a route table that I set to none for a given network of say 20.20.0.0/16 and I have the same route configured on my switch to advertise via BGP I should basically delete the user defined route as it sounds like you are saying the route would default to NONE due to the UDR order preference? Am I understanding correctly?

Aslo can I just delete the routes and leave the subnets for the Route Table or do I need to delete the entire route table. I just want to make sure it doesnt interfere with the BGP routes but want to delete only what is necessary in case I need to put it back.