I have the following set up:
Ubiquiti USG router (WAN: DHCP client: 192.168.20.100/24 GW: 192.168.20.1) Ubiquiti USG router (LAN: DHCP server: 192.168.1.1/24) | Cisco 3750 Switch Port on VLAN 1 (LAN: DHCP client: 192.168.1.100/24 GW: 192.168.1.1) Cisco 3750 Switch Port on VLAN 2 (LAN: DHCP server: 172.27.71.1/24) | PC (LAN: DHCP client: 172.27.71.100/24 GW: 172.27.71.1) Cisco 3750 Switch Port on VLAN 3 (LAN: DHCP server: 172.27.72.1/24) | Server (LAN: DHCP client: 172.27.72.100/24 GW: 172.27.72.1)
Now in order to get it working I configured IP routing and DHCP on the 3750. This allow the PC and server to communicate via the Cisco switch as it is their common gateway.
In order to get internet access to the Server, I added a static routes:
In the Ubiquiti USG: 172.27.0.0/16 via 192.168.1.100
But this didn't work! In order to get it to work I had to add another static route to the upstream router:
172.27.0.0/16 via 192.168.20.100
Now we are getting to the questions:
If the Ubiquiti USG is NATing the outbound traffic, then why do I need to add a static route to the upstream router that includes the 172.27.2.0/24 subnet, isn't this out of context?
The Ubiquiti USG performs bandwidth accounting, but it doesn't list the server or the phone in its client list, it only lists the Cisco switch. If the Cisco switch does not perform NAT then why is the traffic being attributed to the switch?
What do I need to change in my setup to make the USG aware of the devices connected to the Cisco switch - while still allowing inter-Vlan communication to occur on the Cisco switch?
I know I could get it to work by defining all the VLANs on the USG and running a DHCP server for each and just running a trunk to the Cisco switch (i.e. router on a stick) but then all the inter-VLAN traffic between the vlans would have to go via the USG and that is significantly slower.