I need to run OSPF in a little scenario where I am using GRE over IPSec.
I am using FRR plugin and did a simple test by following the first example in the docs (https://docs.opnsense.org/manual/how-tos/dynamic_routing_ospf.html#setup-ospf-between-routers). The other device is not another OPNSense firewall. Yes, I also set the tunable as advised (https://docs.opnsense.org/manual/dynamic_routing.html) and I have set an interface firewall rule allowing ospf protocol traffic input on gre1 interface (I turned off the automatic firewall rule option per the referenced doc).
The problem is there is no communication from the firewall. To verify, I run tcpdump from the firewall cli to sniff the gre1 interface and I can only see the neighbor's hello packets. I am noticing a lot of warnings in FRR log file (Routing | Diagnostics | Log) such as the following:
ospfd - interface gre1: 172.16.3.1: ospf_read network address is not same [172.16.3.2]
The GRE interface is on 172.16.3.0/30. The firewall is *.1 and neighbor *.2.
okay now have some chatter going on. But I am seeing packets getting dropped by the neighbor with the following explanation:
dropping Hello from 172.16.3.1 - network mask mismatch 255.255.255.252 and 0.0.0.0
I can see in the tcpdump on the firewall, hello's come in from the neighbor with a mask of 255.255.255.252 (/30) which matches it's GRE interface, but the firewall is sending a mask of 0.0.0.0.
How do you ensure OPNSense sends a mask in its hello packets?