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Asked: 2021-10-18 00:28:30 +0800 CST

How to configure bird OSPF for ipip link?

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I have a simple ipip tunnel between 192.168.56.254/31 and 192.168.56.255/31.

My simple test config on 192.168.56.254/31 looks like:

protocol ospf test
{
        import none;
        export none;

        area 0.0.0.0 {
                interface "ipip-tun" {
                        cost 5;
                        type ptp;
                        authentication none;
                        neighbors {
                                192.168.56.255;
                        };
                };
        };
}

192.168.56.255/31 is a Mikrotik router. Both instances can't see themselves.

In tcpdump on 192.168.56.254/31, I see:

08:26:11.634115 IP 192.168.56.254 > 224.0.0.5: OSPFv2, Hello, length 44
08:26:11.990261 IP 192.168.56.255 > 224.0.0.5: OSPFv2, Hello, length 44

In the packet sniffer on the Mikrotik device I can see the transmitted packages (also to the multicast address) but no received one.

It confuses me that even the ptp mode uses multicast. Is this normal? If yes, are any configurations for the ipip tunnel required to make multicast work?

linux routing mikrotik multicast ospf

1 Answers

  1. IPIP tunnel supports unicast only while OSPF ptp runs on mcast, that's why you're not getting the packet on the other side. If you need multicast, use GRE tunnel.

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