All things related to multicast

[Matthew Davy <>]

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So based on http://www.iana.org/assignments/multicast-addresses,  
which seems to be the authoritative source of multicast address  
assignment, the IANA reserved space is:

224.1.0.0 - 224.1.0.37  Reserved                            [IANA]
224.1.0.39 - 224.1.0.255 Reserved                           [IANA]
224.1.5.0 - 224.1.255.255 Reserved                          [IANA]
224.3.0.64 - 224.3.255.255     Reserved                        [IANA]
224.5.0.0 - 224.251.255.255  Reserved                          [IANA]
225.0.0.0 - 231.255.255.255 Reserved                 [IANA]
234.0.0.0 - 238.255.255.255 Reserved                     [IANA]

Along with the 232/8 and 239/8 spaces, that covers all the groups in  
the long list I sent out initially.     We could either block all of  
these, or do what Lenny suggested and just allow MSDP for 224/8 and  
233/8, essentially ignoring the reserved blocks inside 224/8 in order  
to have a more manageable filter.     I think the latter is a better  
option as it covers the vast majority of the reserved space and seems  
less likely a new address assignment would accidentally slip through  
unnoticed.

IMO this is definitely the "right thing" to do (regardless of the  
benefits) and would go a long way to accomplishing all the potential  
goals that Bill Owens mentioned.

- - Matt





On May 29, 2006, at 9:04 AM, Pekka Savola wrote:

> On Mon, 29 May 2006, Stig Venaas wrote:
> > In general I wouldn't recommend blocking reserved space. It makes  
> > it very hard for some of the space to become un-reserved in the  
> > future if you see what I mean. If at some point some of this space  
> > should be unblocked, it might be hard to get everyone to open up.
> >
> > Of course as an administrator I might want to block it, knowing  
> > that I would be able to unblock my routers if necessary...
>
> FWIW, I wouldn't recommend such blocking to end-sites, but for  
> (hopefully :-) well-administrated backbones, preventing reserved  
> space abuse and scanning would seem like a good thing to do.  That  
> way the users of that backbone might not need to make that blocking  
> themselves.
>
> Pekka

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