From: Charles Huang (CharlesNY2000@xxxxxxxxx)
Date: Sun Oct 21 2001 - 13:57:45 GMT-3
Does anybody know the reserved private multicast address range ? like the priva
te address for IP in
RFC 1918 ?
----- Original Message -----
From: "Brian Hescock" <bhescock@cisco.com>
To: "Brant Stevens" <branto@myrealbox.com>
Cc: <ccielab@groupstudy.com>
Sent: Sunday, October 21, 2001 12:48 PM
Subject: Re: multicast tip
> People seem to use it anyway... ;-) And for every one we see I'm sure
> there are 10 times that out there where people do the same thing but
> then try another address (that isn't reserved) and it works. It was
> just a fyi so people don't make the simple mistake we see.
>
> B.
>
> Brant Stevens wrote:
>
> >224.0.0.x is a reserved address group...
> >----- Original Message -----
> >From: "Brian Hescock" <bhescock@cisco.com>
> >To: <ccielab@groupstudy.com>
> >Sent: Sunday, October 21, 2001 11:18 AM
> >Subject: multicast tip
> >
> >
> >>The previous discussion about multicast made me think about a problem I
> >>see occasionally and I thought I'd pass it along. Don't use anything in
> >>the 224.0.0.x range for a multicast address. It will work fine if the
> >>source and destination are in the same vlan (unless you're using one of
> >>the reserved addresses, such as 224.0.0.10 for eigrp, which would
> >>probably wouldn't be a good thing to do... ;-). The reason it doesn't
> >>work when routing multicast is the 224.0.0.x is a "link-local" address,
> >>it never gets forwarded off the local segment, you will never get ip
> >>multicast for 224.0.0.x to work across a router unless you bridged it
> >>(haven't tried it but it should work).
> >>
> >>Most people wouldn't use 224.0.0.x but I see it happen occasionally and
> >>wanted to help save some people the grief of troubleshooting the problem
> >>if you used that range of addresses by mistake. Another common problem
> >>in production networks is many multicast servers have a default ttl of 1
> >>and, since one of the first things a router does is decrement the ttl by
> >>one, the packets get dropped at the router. The solution is to increase
> >>the ttl of the multicast server to be at least one higher than the
> >>number of hops to the furtherest multicast receiver.
> >>
> >>Brian
> >>
> >>p.s. in case anyone was wondering, the previous e-mail with my comment
> >>about mutlicast being on by default was referencing a discussion about
> >>NLSP, not ip multicast (the part about NLSP was further down in the
> >>e-mail thread).
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