multicast setup with bond

[unre4l]

Hello,
I am trying to setup bonding and multicast on a RHEL4 update 5 box. Can someone tell me what steps I would have to take to do that? I have setup bonding for another ip on the same box and that works fine. Created an ifcfg-bond0 and assigned ifcfg-eth2 and ifcfg-eth3 as slaves to bond0. Are the bonding steps same for multicast too? I am trying to do this for eth0 and eth1 now.

Is there anything I have to do to enable multicast? Also are their any best practices when assigning multicast addresses or can I use any ip in the range 224.0.0.0 - 239.255.255.255? What would be a normal ip that a typical multicast enabled server would have?
I have to do this on 2 other servers too, so do I just incrementally assign ip's?

Thanks for your help.

[Matti_Kurkela]

Bonding is mainly a Layer-2 function that makes two or more interfaces look like one in the viewpoint of Layer-3 (i.e. everything that uses IP addresses).

So the IP multicast should work with a bond just the same as with a regular NIC.

A quick Google search on "IP multicast address" gives as a first link this document by Cisco:
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ipmulti.htm
It seems to contain a good overview of the rules and practices of the multicast address space.

A normal IP address for a multicast-enabled server is just that - a normal IP address. The address range 224.0.0.0 - 239.255.255.255 is used as multicast *destination* addresses. It is an error to use them as *source* addresses for any traffic.

From the above, you should realize that IP multicast works very differently from the usual IP unicast or broadcast. A multicast address does not identify a server: it identifies a *group* of hosts that wish to receive some specific traffic.

Everything that is required for basic sending and receiving of IP multicast traffic is included in the standard Linux kernel: just start up a program that can use multicasts, configure a multicast IP address, port number and maybe a TTL value and you're ready. The OS will automatically send an IGMP message addressed to the multicast routers of the local network segment(s) to announce that the host wants to participate to the multicast traffic of that group.

You need more software only if you intend to use Linux in routing the multicast traffic between network segments. Multicast routing seems to be a fairly complex field, and I don't really know very much about it - other than that it's very different from regular IP routing.

MK

[unre4l]

Thanks for the reply. So if I understand right then you set up a multicast ip say 224.0.0.1 on all the machines that you want to be in this group? And then use the regular bonding technique to make the nic's failover? Nothing else needs to be done in any config files for the kernel or in terms of network for the bonding.
I'll try it out soon but was just wanted to be clear on how it works. Thanks.