erwan at seanodes.com
Tue Aug 21 08:09:24 UTC 2007
Fajar A. Nugraha wrote:
> Patricio A. Bruna wrote:
>> Does cluster suite use Multicast in Red Hat 5?
>> If is so, how can i test my Switchs allow multicast traffic?
> The switches that I tested allow multicast traffic by default.
> You can test it by running some programs that uses multicast address, like :
> - ping 220.127.116.11. Note that by default RHEL ignores broadcast pings, so
Regarding the **IANA Guidelines for IPv4 Multicast Address Assignments
using some 224.0.0/24 based addresses will bypass some multicast mecanisms.
The 224.0.0/24 addresses are dedicated to the local network routing
messages meaning all ports of your switch will receive this traffic.
But for the others multicast addresses, 3com/cisco and most of high end
switches need to be configured to do the routing.
I mean you can find the "snooping" and the "querier/query" options in
the multicast's switch configuration. Regarding the configuration, the
mulitcast will works or not.
Snooping Off: all multicast traffic works
Snoop On: query off: Mcast is not working except for 224.0.0/24
Snoop On, query on: all multicast traffic works
This have been confirmed on a 3com 3870 switch. Its default
configuration is set on "snoop on/query off".
In such configuration, you must enable the "query/querier" option at
least on a switch to make the multicast working.
So pinging 224.0.0/24 could generates some false positive results
because in some configuration 224.0.0/24 could works whereas all the
other multicast adresses are not.
On some low & middle end switches (dell etc..), activating the snooping
enable the "querier" at the same time so this situation doesn't exists.
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