MX VPN One-armed Concentrator Mode - Layer3 switch needed?

[whistleblower]

Hi Guys,

when I look at the following network plan (https://meraki.cisco.com/lib/pdf/meraki_whitepaper_vpn_redundancy.pdf), I don't understand - why a Layer3 switch is used/necessary in this scenario? wouldn't it make more sense to "connect" the MXs from L3 perspecitve directly on the 3rd party firewall?

Assuming the layer3 switch terminates the customer vlan`s /w ip-subnets you could also regulate this traffic on the FIrewall?!

I appreciate every opinion - thank you!

[cmr]

You could use a firewall as the network core indeed, it is simply historically usual that you use a L3 switch at a site core for performance reasons. 

[whistleblower]

ok - thank you! But do you think that this would be dramatic in todays LAN`s as well?