CODEWITHSUNDEEP
azureroutes
averagescripter
averagescripter

Reputation: 123

How to see Azure system default routes

I checked this page:

https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview

And sentence #2 is:

Azure automatically creates a route table for each subnet within an Azure virtual network and adds system default routes to the table.

So, how do I see these default routes?

Upvotes: 6

Views: 9234

Answers (2)

Aditya Garg
Aditya Garg

Reputation: 66

Happen to notice that a subnet by default does not explicitly have a RT attached to it(though it exists in back end). Looks there is no table as such to view the SYSTEM routes.
Default System routes not shown in portal
It must be noted that:
1.Each subnet can have zero or one route table associated to it(NO MORE THAN 1).
2.When you create a route table and associate it to a subnet, the table's routes are combined with the subnet's default routes. If there are conflicting route assignments, user-defined routes will override the default routes.

3.Routing process:
i.Pick the entries which match with the packet destination(Routes usually specify entire nw in table, packet destination is matched to see it falls in which network entry)

ii.Longest prefix in case of multiple matches:
For example, a route table has two routes: One route specifies the 10.0.0.0/24 address prefix, while the other route specifies the 10.0.0.0/16 address prefix. Azure routes traffic destined for 10.0.0.5, to the next hop type specified in the route with the 10.0.0.0/24 address prefix, because 10.0.0.0/24 is a longer prefix than 10.0.0.0/16, even though 10.0.0.5 is within both address prefixes.

iii.If multiple routes contain the same address prefix, Azure selects the route type, based on the following priority:
>User-defined route
>BGP route
[Caveat:System routes for traffic related to virtual network, virtual network peerings, or virtual network service endpoints, are preferred routes, even if BGP routes are more specific.]
>System route

How Azure does Routing using Route Table

Upvotes: 2

Taguada
Taguada

Reputation: 486

On the Portal you see it through your Network Interface. For example you can select a NIC for one of your VM which is in your subnet that you want to see all of routes. There is an option 'Effective Route'.

[effective routes

You can also see more details in Network Watcher.

network watcher

Same through powershell

PS C:\>Get-AzureRmEffectiveRouteTable -NetworkInterfaceName "MyNetworkInterface" -ResourceGroupName "MyResourceGroup"

Upvotes: 4

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