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Bug with multicast and multiple interfaces, Mac OS X client 9.x (and 6.3.029)


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It seems that the client only registers for multicast request on the first active interface. If another interface comes up, it will not register (and respond) on that interface. In addition, if the first interface is taken down, the client doesn't reregister on the remaining active interface(s), which means that it now will not respond on any interface.


I have verified this with "netstat -g" and my own retrospect multicast client querier hack.


This has become a huge problem to us. At our site we have a WiFi network that won't relay multicast but that everyone is always connected to. When people want backup they have to connect an ethernet cable too. But even if they do, the client won't register for receiving the queries on the wired interface, and they will not get a backup. Even if they disable the wavelan interface, they still will not get a backup. They have to first turn of wavelan, and then connect the ethernet cable to get backups.


I strongly believe that the client should register and respond on all active interfaces (and that the response of course should contain the ip address of the interface the query was received on).


We think that this has worked before, and that the problem started around the end of january 2012, somewhere around the updates 10.7.3 and 10.6 Security Update 2012-001. Maybe something has changed in the IP stack around that time that causes this new behavior.


The problem seems to be exactly the same with both the 9.0.0 (319) and the 6.3.029 clients.



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I have seen a variation of this.


Client 6.3.029 running on Mac OS X 10.5.8 (PPC mini), newly installed.

Server 9.0.1 (401) running on 10.5.8, Intel mini, same network segment - 192.168.0.x


The server would not "see" the client, so I could not "add" the client.


I added it manually by putting in the IP address, and it added fine.

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