Cable Modem connection on F5 Link Controllers

We recently installed 2 F5 Link Controllers to allow for load balancing our ISPs. They are currently in the data flow and are handling our traffic but we are not load balancing between the 2 existing ISPs. We are attempting to connect some "cheap" bandwidth for Internet by adding a bank of cable modems and DSL modems to one of the extra interfaces on the F5s. I have the interface on the F5s added to the VLAN as a tagged interface (since we're going to have multiple cable/dsl modems on this connection and each will have their own subnet). The connectivity is as follows;

 

 

cable modem---switch----F5s

 

 

The switch has the VLAN created on it. The port where the cable modem is connected is an access port in that VLAN. The ports where the F5s are connected are set for 802.1q (aka Cisco Trunking, not to be confused with F5 trunking which would be Cisco's etherchannel). For testing purposes I configured an IP address for the VLAN in question on the switch.

 

 

The switch can ping the Cox default gateway.

 

The switch can ping the F5s

 

The F5s can ping the switch

 

The F5s cannot ping the Cox default gateway

 

 

We've gone over the configuration numerous times and are certain that the subnet masks and IP addresses are correct. We've had the ISP on the phone and they've checked the cable modem. They can see an ARP entry for the IP address that's on the switch but they do not see an ARP entry for the IP addresses on the F5s.

 

 

Has anyone tried connecting cable modems to Link Controllers before? If so, did you have this particular issue or anything similar to this?

 

 

Thanks!