[Xorp-users] Fwd: Fwd: Problem in IPv6 SSM Multicast

Hansi hantongs at gmail.com
Wed Dec 5 05:40:05 PST 2007


Hello Pavlin,

I've consulted w/ the VLC authors and everything appears to be alright w/
the VLC player according to them. Weird... anyway, I'll review my setup. I
might have overlooked something though..

Thanks for your assistance.

Hansi
On Dec 5, 2007 2:46 AM, Pavlin Radoslavov <pavlin at icir.org> wrote:

> > > > > show mld group
> > > >
> > > >
> > > > Interface    Group           Source          LastReported Timeout V
> > > State
> > > > sk0          ff02::2         ::
>  fe80::219:5bff:fe85:cfc7
> > > > 243 1     E
> > > > sk0          ff02::d         ::
>  fe80::219:5bff:fe85:cfc7
> > > > 243 1     E
> > > > sk0          ff02::16        ::
>  fe80::219:5bff:fe85:cfc7
> > > > 243 1     E
> > > > sk0          ff02::1:ff00:1  ::
>  fe80::219:5bff:fe85:cfc7
> > > > 243 1     E
> > > > sk0          ff02::1:ff2f:1468 ::
>  fe80::219:5bff:fe2f:1468
> > > > 248 2     E
> > > > sk0          ff02::1:ff85:cfc7 ::
>  fe80::219:5bff:fe85:cfc7
> > > > 243 1     E
> > > > sk0          ff02::2:15ba:6cf7 ::
>  fe80::219:5bff:fe85:cfc7
> > > > 243 1     E
> > >
> > > It doesn't seem that the client/receiver with IPv6 address
> > > 2001:ec2:4002:fa11:200:24ff:fec4:3235 has joined group ff3e::1234.
> >
> >
> > The ipv6 address 2001:ec2:4002:fa11:200:24ff
> > >
> > > :fec4:3235 is the address of the streaming server. :)
> > >
> >
> > > So your guess in your original email is correct: there is something
> > > wrong with the receiver so it hasn't joined the multicast group.
> > > Could you run tcpdump to capture all ICMPv6 (incl. MLD) traffic and
> > > confirm that XORP is sending the periodic query messages, but the
> > > receiver itself never sends MLDv2 Join messages.
> >
> >
> > Here are the logs from tcpdump taken on the LAN side of the router
> (router
> > ----- receiver)
> > 20:24:32.872230 IP6 (hlim 1, next-header: Options (0), length: 36)
> > fe80::219:5bff:fe85:cfc7 > ip6-allnodes: HBH (rtalert: 0x0000)
> (padn)[icmp6
> > sum ok] ICMP6, multicast listener query, length 28v2  [max resp
> delay=10000]
> > [gaddr :: robustness=2 qqi=125]
>
> OK: the router sends the Query
>
> > 20:24:32.876596 IP6 (hlim 1, next-header: Options (0), length: 32)
> > fe80::219:5bff:fe85:cfc7 > ff02::16: HBH (padn)(rtalert: 0x0000) [icmp6
> sum
> > ok] ICMP6, multicast listener report, length 24max resp delay: 0 addr:
> > ff02::16
>
> OK: MLDv1 Report from the router itself that it is a member of group
> ff02::16
>
> > 20:24:32.892588 IP6 (hlim 1, next-header: Options (0), length: 32)
> > fe80::219:5bff:fe85:cfc7 > ip6-allrouters: HBH (padn)(rtalert: 0x0000)
> > [icmp6 sum ok] ICMP6, multicast listener report, length 24max resp
> delay: 0
> > addr: ip6-allrouters
>
> OK: MLDv1 Report from the router itself that it is a member of group
> ip6-allrouters
>
> > 20:24:32.906594 IP6 (hlim 1, next-header: Options (0), length: 32)
> > fe80::219:5bff:fe85:cfc7 > ff02::d: HBH (padn)(rtalert: 0x0000) [icmp6
> sum
> > ok] ICMP6, multicast listener report, length 24max resp delay: 0 addr:
> > ff02::d
>
> OK: MLDv1 Report from the router itself that it is a member of group
> ff02::d
>
> > 20:24:32.906613 IP6 (hlim 1, next-header: Options (0), length: 32)
> > fe80::219:5bff:fe85:cfc7 > ff02::1:ff00:1: HBH (padn)(rtalert: 0x0000)
> > [icmp6 sum ok] ICMP6, multicast listener report, length 24max resp
> delay: 0
> > addr: ff02::1:ff00:1
>
> OK: MLDv1 Report from the router itself that it is a member of group
> ff02::1:ff00:1
>
> > 20:24:32.906634 IP6 (hlim 1, next-header: Options (0), length: 32)
> > fe80::219:5bff:fe85:cfc7 > ff02::2:15ba:6cf7: HBH (padn)(rtalert:
> 0x0000)
> > [icmp6 sum ok] ICMP6, multicast listener report, length 24max resp
> delay: 0
> > addr: ff02::2:15ba:6cf7
>
> OK: MLDv1 Report from the router itself that it is a member of group
> ff02::2:15ba:6cf7
>
> > 20:24:32.910605 IP6 (hlim 1, next-header: Options (0), length: 32)
> > fe80::219:5bff:fe85:cfc7 > ff02::1:ff85:cfc7: HBH (padn)(rtalert:
> 0x0000)
> > [icmp6 sum ok] ICMP6, multicast listener report, length 24max resp
> delay: 0
> > addr: ff02::1:ff85:cfc7
>
> OK: MLDv1 Report from the router itself that it is a member of group
> ff02::1:ff85:cfc7
>
> > 20:24:37.389295 IP6 (hlim 1, next-header: Options (0), length: 36)
> > fe80::219:5bff:fe2f:1468 > ff02::16: HBH (rtalert: 0x0000) (padn)[icmp6
> sum
> > ok] ICMP6, multicast listener report v2, length 28, 1 group record(s)
> [gaddr
> > ff02::1:ff2f:1468 is_ex { }]
>
> OK: MLDv2 Report from the client that it is a member of group
> ff02::1:ff2f:1468 for all sources.
>
> It appears that the MLDv2 join mechanism between the client and the
> router is working for group ff02::1:ff2f:1468 (which is the group
> automatically joined by the kernel on the client's interface).
>
> However, I don't seen any join for the multicast group from the
> client's application.
>
> > Back when I was exploring ipv4 ssm, everytime I click either on the play
> or
> > stop button of the vlc client, I always see an IGMP join or prune
> message.
> > Shouldn't  it that it also applies to MLDv2? However, I'm not seeing any
> > here.
>
> I am not familiar with vlc, but what you say is the logically
> expected behavior.
> You might want to contact the vlc author(s) about that.
>
> > > BTW, what about MLDv1 Join messages? If you configure the client to
> > > join some (*,G) multicast group does it initiate MLDv1 Join?
> > >
> > My current setup is intended for PIM-SSM traffic. Can it also apply to
> PIM
> > SM considering the setup consist of only two routers?
>
> Yes, you can, but then you must configure one of the routers as the
> RP. For testing purpose you could just try without any
> RP. Obviously, multicast routing won't work, but the "show mld
> group" output will tell us whether MLDv1 Join works for the
> application (and whether the router will record that).
>
> Regards,
> Pavlin
>
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