[Freeciv-Dev] Re: (PR#13245) Catalyst 6500 crashes after several users join to play in network mode

["Peter Schaefer" <peter.schaefer@xxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=13245 >

I searched the sourcecode for this:
It seems to be true that a multicast is used, although the format used
by freeciv to specify it is 225.0.0.1

freeciv can be told to use another multicast port by setting the
environment variable
FREECIV_MULTICAST_GROUP
to a different broadcast IP

I have no idea what the multicast is necessary for, but to work, it
should be specified by client and server.

On 6/9/05, Tamara, Enrique <enrique.tamara@xxxxxx> wrote:
> 
> <URL: http://bugs.freeciv.org/Ticket/Display.html?id=13245
> >
> 
> Hello,
> 
> I'd like to report a problem we have detected when playing Freeciv in
> network mode (several clients playing with a server). The switch which
> connects all of the users is a Cisco Catalyst 6500 and it crashes
> everytime we play the game. We also reported this problem to Cisco TAC,
> but they state this is a normal problem due to the fact that the game
> uses a reserved multicast address (0100.5e00.0001) and traffic is
> directly forwarded to the Catalyst CPU. They say that excessive
> multicast traffic to reserved multicast addresses can easily make the
> switch crash.
> 
> I find all this hard to believe (this could be a very easy DoS attack),
> and I wanted to know your opinion. Have you ever been reported on this
> problem? Do you really think this is normal? Is there any possibility to
> make the game use a different multicast address?
> 
> Thank you very much for your attention.
> 
> Kind regards,
> 
> Enrique
> 
> 
> 
>  
> Hello, 
>   
> I'd like to report a problem we have detected when playing Freeciv in
> network mode (several clients playing with a server). The switch which
> connects all of the users is a Cisco Catalyst 6500 and it crashes everytime
> we play the game. We also reported this problem to Cisco TAC, but they state
> this is a normal problem due to the fact that the game uses a reserved
> multicast address (0100.5e00.0001) and traffic is directly forwarded to the
> Catalyst CPU. They say that excessive multicast traffic to reserved
> multicast addresses can easily make the switch crash. 
>   
> I find all this hard to believe (this could be a very easy DoS attack), and
> I wanted to know your opinion. Have you ever been reported on this problem?
> Do you really think this is normal? Is there any possibility to make the
> game use a different multicast address? 
>   
> Thank you very much for your attention. 
>   
> Kind regards, 
>   
> Enrique  
>