How to setup C9300 for L3 Routing

[Holli69]

Hi,

We've an office with MX105 as Firewall, C9300-24Y-M as the Core L3 Switch with Routing, and a few MS225-48-FP/LP as Access Switches.

I can see MX105 in Meraki Dashboard online and C9300-24Y-M with a Transfernet to MX105 is online as well.

We have about 10 Subnets on C9300 configured, each MS225 Switch connected via SFP+ to core Switch C9300 doesn't come online on the Management VLAN and get no reserved IP from the DHCP Server (C9300). So all MS225 switches are marked as red (LED and Dashboard).

With a MS250-24 as Layer 3 switch everything works fine.

Question: Is there a way to force the routing function on the C9300 ? It seems routing isn't working on the device

[KH]

Hello Holli,

We would need more information on your setup, was the MS250 migrated to the c9300 with the same exact configuration? Does the MS250 when working, use the same config as the C9300? Can you share the output of your Addressing & VLANs page from the MX as well as the Routing & DHCP page for your switches?

[GIdenJoe]

If the C9300 is the L3 switch, first make sure that switch has a mgmt IP in a VLAN that exists directly behind the MX so that swtich can come online and receive it's config.

Then you create your SVI for  your uplink towards the MX with the default route in one go and then can you make each SVI.

[Tony-Sydney-AU]

Hi @Holli69 ,

It's like @KH said, We need to know more information.

I think this article can help you. Perhaps you forgot about having a transit vlan in your C9300 (vlan 50 in the example).

Remember that you cannot use management VLAN IP as the same IP in Transit VLAN interface.

[Holli69]

Hello everyone,

we have a Transit VLAN 10 (10.105.10.252/30) between MX105 and C9300-24Y-M, MX IP is 10.105.10.254, C9300 (Layer3) IP is 10.105.10.253.

The C9300 takes care of all L3 Routing, all SVI's are configured on this Switch.

Also the Mgmt VLAN 20 for all Meraki Layer 2 Switches and Meraki Access Points (10.105.20.0/24) with fixed IP Assignments on the L3 DHCP Server. 

This is the first time we have used C9300 as a Layer 3 Switch, before we used MS250-24 as Layer 3 Switch and everything works fine for us.

[Holli69]

Hello again,

strange behaviour, from MX I can ping L3 Switch, but from L3 Switch (IP: 10.105.10.253) I can't ping IP of MX (IP: 10.105.10.254) or 8.8.8.8 (100% loss). Nothing is blocked by ACL or Firewall.

[jedimaster]

Fascinating that we both are experiencing the same problem with the exact same gear.

[Tony-Sydney-AU]

Hi @Holli69 ,

If you can't ping from C9300 to MX, maybe it's related to VLAN.

I'm assuming the IP 10.105.10.253 is not the C9300 management IP.

What are the port configurations in each case?

a) MX port connecting to C9300? is it a Trunk or Access? VLANs?

b) C9300 connecting to MX? is it a Trunk or Access? VLANs? 

[Holli69]

Hi Tony,

a) MX port connecting to C9300 in an access Transfer VLAN 10 with 2 IP's

MX has 10.105.10.254, C9300 has 10.105.10.253 in a subnet of 10.105.10.252/30.

b) there is only one 10G Fiber connection between those 2 devices, configured as an access port on both ends, both in VLAN 10 (transfer net). The C9300 takes care of the management VLAN 20, but either the MX nor the C9300 has a management IP from VLAN 20.

With MS250-24 instead of C9300 exactly this config works fine in all other locations.

I can ping from MX to C9300, but I can't ping from C9300 to MX and I can't ping to 8.8.8.8, but the C9300 is reachable from the Meraki Cloud and is online.

So, I assume there is something different between C9300 and MS250 or other "legacy" Meraki Switches.

[jedimaster]

I have had similar difficulties getting a Cisco Catalyst (in Meraki mode) to act as our Layer 3 network core/router.  It sits directly behind an MX-250.  An existing Meraki MS250 has the duty right now, but with the same routes and interfaces, the 9300 can't get online.