So i'm configuring L3 routing on my network and wanted to check if i'm right.
I have my following setup
MX250 - Corestack MS410 - Serverstack MS250
MX and MS410 have a 10.0.18.0/24 network for going towards the internet MX = 10.0.18.1, This created a default route 0.0.0.0/0 towards 10.0.18.1
The MS410 have the L3 interfaces but now i want to route 10.162.128.0/17 to IP 10.162.128.1 (Alcatel L3 switch of 3rd party here in the building)
That alcatel switch is in Port 1 of switch 1 of my server switches. trunk port with the VLANS of that switch.
When I do not create a L3 interface for this subnet i get the error "not in a configured subnet"
When i do create one it says "already routed"
I have over 20VLANS so the 0.0.0.0/0 is very handy but I'm starting to think I have to create a route for every subnet and remove the 0.0.0.0/0 route to be able to define a different route for that subnet?
You can't route 10.162.128.0/17 to 10.162.128.1 - they are both in the same subnet - that would be pointless. Does the Alcatel have another layer 3 interface in a different VLAN that any of your other kit is also in? You could add the 10.162.128.0/17 via that other interface.
If the Alcatel only has that one layer 3 interface then you don't need to route anything via it (you need at least two layer 3 interfaces to really do routing). In that case you would simply add a layer 3 interface for that subnet onto one of your other devices, such as your core switches.