FRR transmit issues on interface without gateway
-
For the second time I've run into a strange issue running RIPv2 or OSPF. Before we all go off the rails on why RIP is being used in 2024 let’s just assume the others are locked behind a pay wall for now. In the first instance of this issue, I encountered about three years ago with PFsense and a Dell switch both running RIPv2. They were connected to each other via /29. PFsense was able to receive routes from the Dell without issue, however after some packet captures, I noticed that PFsense was not transmitting any RIP. The result was the same when using v1 or v2 including setting v2 for broadcast. Switching to OSPF is the same as well. The solution oddly enough was to define a gateway on the /29 interface that bridged the two routers. I set the GW of that interface on PFsense as the Dell router. Immediately the Dell started to receive routes from PFsesne.
So, adding a GW to the interface the two routers share was the solution. I didn’t experiment with what was defined as the GW. At the time I just assumed it needed to be defined for some reason for the routing protocol to bind to the interface.
This brings me to the fun I've had for the last two days with PFsense, and a SonicWALL connected via VTI. Similar story. I'm stuck using RIPv2 because BGP is not licensed at the moment. In this configuration however we don't have the luxury of adding a GW to the VTI interface because it’s not that type of interface. I thought about bridging the VTI to a real interface, but I feel that is more of a hack than a solution. For what it is worth I am replacing the SonicWALL with one that is licensed for BGP, but it would be nice to know if I am doing something wrong or there is something else here that would explain what I encountered.
Edit:
let me be clear about what I mean as a gateway. In PFsense you can have a gateway defined, but not selected in an interface config screen. In my case the router bridge interface properties did not have this GW selected when we were not transmitting any routes. Once I selected this router, I could see packets being sent with routes belonging to PFsense. So I do have a GW defined and is replying to pings, but it is not possible to select it in the VTI interface for obvious reasons. I know this config will work with BGP because I have others set up like this.