Zixi Multicast Deployment Guid...

Troubleshooting

1min

This section provides troubleshooting advise for some common multicasting-related issues.
Issue
Probable Cause
Solution
No multicast bitrate on Linux – The multicast stream is either 0 bitrate immediately, or its bitrate starts to drop to 0 after a while
Although typically this is an OS configuration or network configuration issue, it could be caused by the Zixi configuration.
In Zixi, make sure the correct local IP address is specified in the UDP input.
When using IGMPv3 - verify that correct SSM source IP is specified.
Leave the SSM field blank to allow accepting the multicast from any IP
Verify if the multicast is joined to the right group with ‘netstat -ng’
Monitor incoming traffic with tcpdump - see if it physically gets into the machine and then blocked in software, or if it doesn’t physically get there.
If it doesn’t get into the machine - this is a network issue.
If it gets to the machine but our application still shows 0 bitrate - it can be a routing/source IP issue.
Use 'socat' as a useful debug tool to verify if another program can get the data on the same machine.
If 'socat' can create a file - but our software can't see bitrate - this can be a bug. Contact R&D.
If the machine gets traffic in tcpdump, but not in software (ours or socat), then something is blocking it locally.
Verify that the source of the multicast is in the same subnet of the IP receiving it, or that there is a proper routing rule directing the multicast to the listening IP.
Verify the value of rp_filter (cat /proc/sys/net/ipv4/conf/eth0/rp_filter) - set it to 0 if needed (replace eth0 with the proper NIC, set it permanently in sysctl.conf).
Check that there is no firewall that blocks the multicast traffic.
Force IGMPv2 on the OS (rarely needed) -
echo "2" > /proc/sys/net/ipv4/conf/eth0/force_igmp_version
replace 'eth0' with the interface name. (Set it permanently with "net.ipv4.conf.default.force_igmp_version=2" in sysctl.conf)


Traffic on the UDP input on the Zixi Broadcaster side can looks doubled.
The same multicast address is available from multiple IPs (sometimes used for encoder redundancy)
Set rp_filter to 1 (if the multicast source is in the same subnet as the desired input IP).
Use the advanced "filter by SSM source IP" setting.
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Issue	Probable Cause	Solution
No multicast bitrate on Linux – The multicast stream is either 0 bitrate immediately, or its bitrate starts to drop to 0 after a while	Although typically this is an OS configuration or network configuration issue, it could be caused by the Zixi configuration.	In Zixi, make sure the correct local IP address is specified in the UDP input. When using IGMPv3 - verify that correct SSM source IP is specified. Leave the SSM field blank to allow accepting the multicast from any IP Verify if the multicast is joined to the right group with ‘netstat -ng’ Monitor incoming traffic with tcpdump - see if it physically gets into the machine and then blocked in software, or if it doesn’t physically get there. If it doesn’t get into the machine - this is a network issue. If it gets to the machine but our application still shows 0 bitrate - it can be a routing/source IP issue. Use 'socat' as a useful debug tool to verify if another program can get the data on the same machine. If 'socat' can create a file - but our software can't see bitrate - this can be a bug. Contact R&D. If the machine gets traffic in tcpdump, but not in software (ours or socat), then something is blocking it locally. Verify that the source of the multicast is in the same subnet of the IP receiving it, or that there is a proper routing rule directing the multicast to the listening IP. Verify the value of rp_filter (cat /proc/sys/net/ipv4/conf/eth0/rp_filter) - set it to 0 if needed (replace eth0 with the proper NIC, set it permanently in sysctl.conf). Check that there is no firewall that blocks the multicast traffic. Force IGMPv2 on the OS (rarely needed) - echo "2" > /proc/sys/net/ipv4/conf/eth0/force_igmp_version replace 'eth0' with the interface name. (Set it permanently with "net.ipv4.conf.default.force_igmp_version=2" in sysctl.conf)
Traffic on the UDP input on the Zixi Broadcaster side can looks doubled.	The same multicast address is available from multiple IPs (sometimes used for encoder redundancy)	Set rp_filter to 1 (if the multicast source is in the same subnet as the desired input IP). Use the advanced "filter by SSM source IP" setting.

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