On Monday, 22 October 2018 23:10:54 ACDT Rodney Baker wrote:
[...]
224.0.0.1 is the "All hosts" multicast address - it is used by a router to address all hosts on the same network segment. This is used for host discovery. From https://www.tldp.org/HOWTO/Multicast-HOWTO-2.html;
"There are some special multicast groups, say "well known multicast groups", you should not use in your particular applications due the special purpose they are destined to:
- 224.0.0.1 is the all-hosts group. If you ping that group, all multicast capable hosts on the network should answer, as every multicast capable host must join that group at start-up on all it's multicast capable interfaces. - 224.0.0.2 is the all-routers group. All multicast routers must join that group on all it's multicast capable interfaces."
The full Ipv4 multicast address space registry is here; https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xht ml
Unless you are specifically wanting to receive multicast traffic (for example, to participate in dynamic routing protocols e.g. RIP, eigrp, ospf, bgp or is- is), or for receiving multicast video/audio traffic, you should not worry too much about it.
If you want it to work, you'll need to permit traffic to 224.0.0.0/24 on all your firewall interfaces where multicast-capable hosts exist.
The IPv6 equivalent addresses (link-local scope) are FF02::1 (for all hosts) and FF02::2 (for all routers). Node-local (or interface-local) equivalents are FF01::1 and FF01::2.
The full list of well-known multicast addresses for IPv6 are here: https:// www.iana.org/assignments/ipv6-multicast-addresses/ipv6-multicast- addresses.xhtml
Just as a test, I tried to ping 224.0.0.1 on my local lan and got only one response - my L3 network switch which has igmp snooping enabled by default. No other devices responded. I then enabled ip multicast-routing on my router and turned on PIM sparse-mode on the interface for my desktop vlan. Now, when I ping 224.0.0.1, both the router and the switch respond, but if I ping 224.0.0.2, only the router responds (as expected). They're the only 2 multicast-capable devices on the network. [I turned multicast routing off again after the test as I have no need for it at home, although we do use it extensively at work.] R. -- ============================================================== Rodney Baker VK5ZTV rodney.baker@iinet.net.au CCNA #CSCO12880208 ============================================================== -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org