Re: gated[21974]: OSPF RECV 203.176.28.161 -> 224.0.0.5: IP: bad destination

[Yozo TODA <yozo_(_at_)_ipc_(_dot_)_chiba-u_(_dot_)_ac_(_dot_)_jp>]

> gated[21974]: OSPF RECV 203.176.28.161  -> 224.0.0.5: IP: bad destination
> 
> where 203.176.28.161 is an IP address on the other subnet of another router 
> on the same network.  I also recall that 224.0.0.5 is something special...
> what does it mean?

I don't know why "bad destination" but DNS tells

5.0.0.224.in-addr.arpa	name = OSPF-ALL.MCAST.NET

and from RFC2328:

   The other important features of OSPF's IP encapsulation are:

    o   Use of IP multicast.  Some OSPF messages are multicast, when
        sent over broadcast networks.  Two distinct IP multicast
        addresses are used.  Packets sent to these multicast addresses
        should never be forwarded; they are meant to travel a single hop
        only.  To ensure that these packets will not travel multiple
        hops, their IP TTL must be set to 1.

        AllSPFRouters
            This multicast address has been assigned the value
            224.0.0.5.  All routers running OSPF should be prepared to
            receive packets sent to this address.  Hello packets are
            always sent to this destination.  Also, certain OSPF
            protocol packets are sent to this address during the
            flooding procedure.

        AllDRouters
            This multicast address has been assigned the value
            224.0.0.6.  Both the Designated Router and Backup Designated
            Router must be prepared to receive packets destined to this
            address.  Certain OSPF protocol packets are sent to this
            address during the flooding procedure.

-- yozo.