Cisco RV160 - Inter VLAN Routing between Class B & C Networks

[reesejacobs]

The new Cisco RV160 router allows VLANs to be configured with different subnet masks. I have 2 VLANs (VLAN 1 and 18) with networks defined as follows:

VLAN 1 -- IP: 192.168.2.1/255.255.255.0 (24) (ports 1, 2, & 3)

VLAN 18 -- IP: 198.18.64.1/255.255.0.0 (16) (port 4)

Ordinarily, I would have configured the VLAN 18 class B network on the RV160 as 198.18.0.1 but there is a host/DHCP server on that network that uses a fixed IP address of 198.18.0.1 and this can not be changed (it is an automation system device which is the DHCP server for the 198.18 network). The DHCP server on VLAN 18 serves addresses in the range 198.18.0.2-198.18.63.254 while 198.18.64.1-198.18.64.254 are reserved for static IP assignment.

After configuring the VLANs as noted above, I connect a laptop to the RV160 (VLAN 1/port 2) and obtained an address from DHCP (192.168.2.100). From the laptop, I can ping any system on the 192.168.2 network as well as any IP address on the 2nd VLAN as long as the IP is 198.18.64.yy. Any system on VLAN 18 with an IP address of 198.18.xx.yy where xx is anything other than 64 is inaccessible (i.e. ping to 198.18.0.1 does not work). Likewise, any system on VLAN 18 with an IP address of 198.18.64.yy can access the 192.168.2 network. However, any system on VLAN 18 with an IP address of 198.18.xx.yy where xx is not 64 can not access the 192.168.2 network.

I must be missing something basic since I though the above setup of the 2 VLANs (with inter VLAN routing enabled) would work as I expected. I am not sure what additional steps (or configuration changes) are required in order to provide access to *all* IP addresses between VLANs 1 and 18. Any help would be greatly appreciated. Thanks!

[Dennis Mink]

Do you really need a /16 ? Why not a /23 or 22? How manyhosts have you got inthe subnet?

[reesejacobs]

The choice of 16 vs. 22 or 23 is not my choice. Again, it is a limitation of the 198.18.0.1 Host/DHCP server that is on that network. The setup of that system is based on a 198.18 network with a mask of 255.255.0.0. It is fixed and can not be changed.

[luis_cordova]

Hi @reesejacobs ,

Only to discard, verify that the devices of the vlan18, which obtain addresses by DHCP, are acquiring the correct gateway (198.18.64.1).

Regards

[reesejacobs]

Thanks for the suggestion -- that had occurred to me. In checking further, the DHCP server that controls that network seems to be serving its own IP address (198.18.0.1) as the gateway. There is no way to configure a different IP address for the gateway. The DHCP server can be disabled on the network and the RV160 could be used to serve IP addresses to all DHCP clients on VLAN 18 and in doing so, the correct gateway could be served to those clients. The problem is that the DHCP server (198.18.0.1) can not be set to a fixed IP and its gateway can not be configured so it would always be inaccessible. In addition to it being a DHCP server, it is an automation system master controller and access to it via VLAN 18 is desirable. You can configure the class B address components for this server to any valid class B address but it is coded with an fixed IP address of aa.bb.0.1 on whatever you choose for aa.bb (198.18 or otherwise). In other words, the gateway IP address for this server is always its own IP address. Given these limitations, I am not sure how to make inter-VLAN routing work correctly for all hosts on the class B network including the master controller/DHCP server. Thanks again for your suggestion.