If the server has joined the group but you don't see any packet incoming from client, then check on your router that you have enabled igmp your router must be igmp capable For example,on cisco router enable conf t ip multicast-routing For each interface involved.
Improve this answer. Community Bot 1. UnX UnX 4 4 silver badges 8 8 bronze badges. Very long answer and the tiniest part is what actually appeared to be the problem.
The troubleshooting stuff you have mentioned, I already did, but that was after I posted this. Everything looked good on the server and the client. IGMP on the router was the problem, but that setting was hidden — Alex. Michael Michael 11 1 1 bronze badge. WLG v3 Malvineous Malvineous 5, 3 3 gold badges 38 38 silver badges 59 59 bronze badges. We checked the igmp settings on the router, which seemed to be in order.
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Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. Multicast packets, that come from the source, do not trigger the router to send CGMP self-joins to the switch. Therefore the packets hit the switch and get flooded everywhere within the VLAN. Only with the receipt of an IGMP report does the router send a CGMP packet, which then causes the switch to add the appropriate host port as forwarding and all other ports are blocked aside from the router ports.
Now When you use the multicast group address It floods the multicast stream out all switch ports and wastes bandwidth. However, if you change the address to What is wrong with using First, it is important to understand how Layer 3 multicast addresses are mapped to Layer 2 multicast addresses.
Another important fact to understand is there are 28 bits of unique address space for an IP multicast address 32 bits minus the first 4 bits that contain the class D prefix. This means that multiple Layer 3 multicast addresses can map to the same Layer 2 multicast address.
Now that you know how Layer 3 to Layer 2 multicast addresses are mapped, proceed to the specific solution to the this problem.
Switch A floods multicast packets to Catalyst switches also flood multicast packets to other multicast addresses that are MAC level ambiguous with The switch floods the multicast packets destined for these link local addresses whether CGMP is enabled or not. Therefore, the multicast application must avoid the use of class D addresses that map to a Layer 2 multicast address of This consists of these class D addresses:.
Duplicate multicast packets are received when two routers are configured in dense mode. In dense mode, the device periodically floods the stream. After flooding, it prunes off the interfaces where the steam is not wanted. The two routers also go through the assertion process and decide who is the forwarder.
Every time the timers go off this happens, and until this process is complete, both routers forward the stream. This causes the application to receive duplicate multicast streams. This issue can be resolved if you have one of the routers configured for multicast routing and to configure the other router to be the RP in upstream.
Configure it in order to convert the stream into sparse mode before the stream comes into the router. This can prevent duplicate packets from reaching the application. It is not a part of the networks responsibility to ensure that no duplicate packets ever reach an end host.
It is a part of the responsibility of the application to handle duplicate packets and ignore unneeded data. This issue can occur in Cisco Catalyst switches, which are configured for egress multicast replication mode and can be triggered by removal and re-insertion of any line cards [OIR]. The result is that they are looped back to the Fabric and replicated multiple times when they exit on the correct linecard.
As a workaround, change to ingress replication mode. During a change from egress- to ingress-replication mode, traffic interruptions can occur because the shortcuts are purged and reinstalled. Enable the RSS setting on the end-host or server.
It is possible that you see the excessive flushes and input packet drops on the interface s when Multicast traffic flows. You can check the flushes with the show interface command. If multicast packets are process switched on any interface s , it consumes more CPU as it mandates process switching of all packets to that group. You can run the show buffers input-interface command and check the abnormal size.
Note : Due to previous issues, it is possible that you see high CPU usage around 90 percent. CPU comes down to normal when you resolve them with these possible fixes. Skip to content Skip to search Skip to footer. Available Languages. Download Options. Updated: July 15, Contents Introduction. Introduction This document describes common problems and solutions for IP multicast. Prerequisites Requirements There are no specific requirements for this document.
Components Used This document is not restricted to specific software and hardware versions. Background Information When you troubleshoot multicast routing, the primary concern is the source address. Diagnose the Problem Hosts directly connected to Router 75a receive the multicast feed, but hosts directly connected to Router 72a do not. Enter the show ip mroute command in order to see whether Router 72a has good mroute: ipa show ip mroute If the administrative distances are equal, then this order of preference is used: Static mroutes DVMRP routes MBGP routes Unicast routes If multiple entries for a route occur within the same route table, the longest match route is used.
Enter some further debug commands: ipa debug ip mpacket Possible Fixes You can either change the unicast routing table in order to satisfy this requirement or you can add a static mroute to force multicast to RPF out a particular interface, regardless of what the unicast routing table states. Add a static mroute: ipa config ip mroute 1.
You can check to see if it is a TTL issue with the sniffer capture and also seen with show ip traffic command: ROUTERA show ip traffic IP statistics: Rcvd: total, local destination 0 format errors, 0 checksum errors, bad hop count 0 unknown protocol, 0 not a gateway 0 security failures, 0 bad options, 0 with options The output shows bad hop counts.
Diagnose the Problem In the previous figure, the Receiver does not receive multicast packets from the Source. In order to be absolutely sure Router 75a forwards the packets, turn on debug just for this source and multicast group: ipa configure terminal Enter configuration commands, one per line.
Diagnose the Problem In the figure, Router 75b has three equal cost paths back to the Source 1. Possible Fixes In order to change the interface IP multicast chooses as its incoming interface, you can do one of these: Only configure PIM on the interfaces that you want multicast to traverse, which means you lose multicast redundancy. As an example, a static mroute is created. These are the configurations for the tunnel.
Router 75a interface Tunnel0 ip address 6. Possible Fixes The solution is to correct the IP address in the ip pim accept-rp statement as follows: Change this statement: ip pim accept-rp This is an example: ip pim accept-rp auto-rp access-list 8 permit Possible Fixes Either make router2 the RP for the group Now check whether you receive the correct multicast route mroute information on the routers: ipa show ip mroute This output shows Router 75b gets the multicast packets and forwards them correctly: ipb show ip mroute First, turn on debug commands on Router 75b: ipb conf t Enter configuration commands, one per line.
Or move the source on the same subnet as Routers 75a and 75b, as in this example. Possible Fixes First, it is important to understand how Layer 3 multicast addresses are mapped to Layer 2 multicast addresses. For example: This consists of these class D addresses: Possible Fix 1 This issue can be resolved if you have one of the routers configured for multicast routing and to configure the other router to be the RP in upstream. I'd say the most common cause that you'll need to be on the lookout for is routed networks, where the entire set of systems that need to participate in the multicast group the clients and the server are not on the same broadcast domain.
That's the first thing to ask the client's network administrators. As far as resolving it if that is the case, it depends on their networking equipment; they'll need to set up PIM and IGMP snooping on their routing equipment.
Their equipment having support for it may be hit or miss; this may be a major barrier for some of your clients. You may need to look into alternative solutions that don't require their network equipment to play nice with multicast. A couple ideas:. If you have a VirtualBox Host-Only Ethernet Adapter activated on your system that might be the problem, which it was for me, so try disabling it.
You can use a tool like wireshark to watch UDP packets on the troublesome machine. From that you should be able to determine if the UDP packets are even reaching that machine.
I had similar problems while a Hyper-V virtual ethernet adapter advertised as vEthernet default switch was active on my machine. With wireshark I could see the multicast network traffic on my server, but the server application did not respond even though it was registered to the address and port. So the Answer in this case is: Disable the Hyper-V virtual ethernet adapter if it is enabled. Try disabling windows firewall and check if your software is receiving packets.
I had similar problems with my Java program. If firewall is the problem start experimenting with firewall rules for your incoming traffic. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more.
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