enable multicast?

[John McBride]

Brian Fahrlander wrote:
> On Wed, 2004-07-21 at 17:46, Joel Jaeggli wrote:
> 
> 
>>ipv4 Multicast works fine actually. 2.6 even supports igmp3 and mldv2 
>>(for ipv6 multicast) for group membership requests. The problem really is 
>>interdomain multicast support, which frankly isn't getting any better. 
>>Using multicast on you home network or subnet is trivial and all the 
>>pieces are there and available.
> 
> 
>     Sure; the underpinning is there...but though I've heard of _A_
> client out there (other than NTP) for it, and the decade-old documents,
> it's pretty tough for a non-tech guy to get any use of it.
> 

odd we use multicast on our lans to stream realtime data across subnets 
all the time. at least three seperate client/server application stacks, 
running almost continuously.

it's great way to bypass arp, thus allowing a unidirectional connection, 
through, say, a fiber. this is incredibly important in certain environments.

been using it for years, and we have plans for vastly increased usage 
over at least the next couple of years.

no offense, but just because you haven't heard of something, or rarely 
use it, doesn't mean it is not of use, or not used.

in my experience, once one gets a handle on the concept of multicast 
joins, it's a trivial and robust transport. i've used it on irix, linux, 
solaris and bsd with pretty much zero problems with the exception of a 
few flag oddities here and there...and that was a couple years ago.

by the way, ifconfig will multicast enable your ether. see the man page. 
most cards have multicast enabled when they are brought up, so 
/sbin/ifconfig will show the MULTICAST flag set for just about any nic, 
but at least one intel driver does not always set the multicast flag 
properly under fc1--and you must set it by hand or in a init script 
using ifconfig.