Multisite Capacity Plus without routers? 😲

Since its introduction in 2012, the recommendation has always been to make use of Routers in Multisite Capacity Plus systems. While this advice has not changed, it is nonetheless, possible to build a backend network with just ethernet switches at each site.

However, not just any old switch will do! One needs to be careful as Capacity Plus uses IP broadcast to manage on-site activity. If broadcast packets from one site were to arrive at any other RF site, the system would go awry.

The chosen switch, must therefore, be able to prevent all packets with an destination IP address of 255.255.255.255 from entering the backhaul network and other RF sites.

Since no NAT type routing is occurring anywhere in the network, a different IP plan is needed. Essentially, each RF site will need its own subnet. Here is an IP plan which illustrates this:

There are some downsides:

For a 15-site system, an entire block of  IPv4 addresses will need to be allocated to the radio system. If Routers are used, only one IPv4 or IPv6 address is needed per logical site.

This "Routerless" configuration is also not suitable for shared networks where IP addresses are a scarce commodity. However, VLAN can be used to segregate the radio system from the rest of the network and alleviate this problem but this also means that any computer hardware needing to access the radio network will need to be on the same VLAN.

If no Routers are used, the repeaters and any on-site equipment would be exposed to the network. With a Router, you are able to block everything that is not needed or seen as a risk. Essentially, everything behind the router is "hidden" from the network and the curious. Remember that a good proportion of cyberattacks use devices within the network as vectors (e.g. Chinesium IP surveillance cameras).

Personally, I still prefer building Multisite capacity Plus networks using Routers. For a four carrier RF site, adding a well known brand Router to the bill of materials only increases the total cost by around 5%. A Router allows you to do things like link redundancy; IPSec and VPN.