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This is the support site for Andrews & Arnold Ltd, a UK Internet provider. Information on these pages is generally for our customers but may be useful to others, enjoy!

Multicast: Difference between revisions

1,542 bytes added ,  29 August 2022
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= FTTC =
 
<strong>Unofficially and completely at own risk</strong>, it has been found to be possible to watch the [https://community.bt.com/t5/YouView-Boxes/IPC6023-Advanced-Diagnosis/td-p/1154880 Test Channel] as described on the BT website, on an AAISP provided FTTC line. This is [https://community.bt.com/t5/YouView-from-BT/Multicast-Test-Channel-URL/td-p/2223426 updated as of 2022]
 
== Example for Debian GNU/Linux ==
 
Have extracted some paramatersparameters from pppd, this may not work correctly if there is more than one instance.
eval `tdbdump /var/run/pppd2.tdb | grep CALL_FILE | cut -d'"' -f2`
 
AddAs a workaround to IPv4 not customarily allowing ifindex or interface name specification in addresses, (known as scope or "%", in IPv6) route to the multicast group on the device upon which PPPoE runs, aimed at the openreach modem:
 
echo ip route add 234.81.130131.4194 dev $DEVICE
 
Play stream.
Caveats : It starts when the network receives an IGMP join and stops with IGMP leave.
 
ffplay rtp://234.81.130131.4194:5802
 
or:
vlc rtp://234.81.130131.4194:5802
 
=== Relaying the stream ===
 
It may happen that the computer hosting PPPoE is in an inconvenient location for watching and that other networked devices should receive copies of the stream. For real use an IGMP proxy would be used but for first testing [http://troglobit.github.io/smcroute smcroute] lets one tryforward multicast statically at first and can even work where clientsprograms don'tdo sendnot understand IGMP joinor andin leavesome correctlysituations even multicast, butwhich thiscan alsobe meansaided thewith streamDNAT hasrules toand/or beuse manuallyof started-j andREDIRECT stopped.on targets
 
It may be possible later to have other programs listen for IGMP/MLD and then "manage" smcroute, due to a possible linux limitation of only allowing one userspace program manage kernel mrouting at a time, to have maximum flexibility in upstreams and downstreams including internal sources.
For testing, using smcroute we can reflect the multicast to other attached networks. SMCroute does not configure the interface without a legacy IP, so can copy WAN address:
 
Other software that may be useful is [https://manpages.debian.org/stable/igmpproxy igmpproxy] and [https://unfix.org/projects/ecmh/ ecmh]
ifconfig $DEVICE $IPLOCAL
 
For testing and usage, smcroute can reflect the multicast to other attached networks. The smcroute 2.4.4 as found in Debian 11, would not configure the interface without an IP address on it, however the very latest smcroute allows 0.0.0.0 to be used to originate the IGMP3 joins, this needed the upgrade from ip_mreq to ip_mreqn in the smcroute code.
smcroute requires the source address, this was found with wireshark and could be subject to change, <var>int0</var> and <var>ext0</var> are example devices to copy multicast packets to, these could be internal vlans on a home network:
 
Additionally the sysctl rp_filter is disabled on $DEVICE and "all" to allow the incoming multicast without a matching outgoing route, also desirable. iptables and/or nftables would still be used to filter.
smcroute -a $DEVICE <var>109.159.247.1</var> 234.81.130.4 <var>int0 ext0</var>
 
smcroute requires the source address, this was found with wireshark or tcpdump, and could be subject to change, <var>int0</var> and <var>ext0</var> are example devices to copy multicast packets to, these could be internal vlans on a home network:
To actually start:
 
smcroutesmcroutectl -jadd $DEVICE 109.159.247.194 234.81.130131.4194 <var>int0 ext0</var>
smcroutesmcroutectl -aadd $DEVICE <var>109.159.247.1</var>200 234.81.130131.4200 <var>int0 ext0</var>
smcroutectl add $DEVICE 109.159.247.216 234.81.132.216 <var>int0 ext0</var>
 
To actually start, substituting for the other addresses beginning 234. above for the other channels.
 
smcroutectl join $DEVICE 234.81.131.194
 
and stop:
 
smcroutesmcroutectl -lleave $DEVICE 234.81.130131.4194
 
see for forwarding statistics:
cat /proc/net/ip_mr_cache && ip mroute show
 
now ffmpeg, vlc or other client can be ran elsewhere on the internal network, if their ethernet interfaces do not have legacy ip addresses and the client does notallow specifyspecification of an interface for IGMP, usewhich is more usual with ipv6, a workaround is <code>ip route add 234.81.130131.4194/32</code> on these devices with a device aiming towards the PPPoE host system.
 
 
 
== Example Notes ==
* [http://ideas.aa.net.uk/?ia=7937 Votes on the idea]
* [http://www.revk.uk/2012/11/multicast.html AAISP Director on Multicast]
 
* [https://www.bt.com/about/sinet BT] and [https://www.openreach.co.uk/cpportal/help/suppliers-information-notes-(sins) openreach] supplier information notes, especially BT 511 and openreach 503
 
 
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