port mirroring and multicast

It is possible the multicast packets are timing out. It looks like you would apply this to the VLAN interface where the multicast is entering the switch.  ie .. the VLAN that Server 1 is on.  

ip multicast ttl-threshold

Use the ip multicast ttl-threshold command in Interface Configuration mode to apply a ttlvalue to a routing interface. ttlvalue is the TTL threshold which is applied to the multicast Data packets forwarded through the interface.

The following example applies a ttlvalue of 5 to the VLAN 15 routing interface.

console(config)#interface vlan 15

console(config-if-vlan15)#ip multicast ttl-threshold 5

Do you still have configuration for a VLAN on the destination mirror port?  

Can you provide the output of this command for the destination mirror port that is connected to Server 3?

console#show interfaces detail ethernet x/x

Thanks for the reply. 

I tried the multicast ttl-threshold - set to 5, however, it didn't help. I still got no multicast on the mirror destination. Here is the output: 

console#show interfaces detail ethernet 1/g36

Port   Type                            Duplex  Speed    Neg   Admin  Link
                                                              State  State
-----  ------------------------------  ------  -------  ----  -----  -----
1/g36  Gigabit - Level                 Full    1000     Auto  Up     Up     


Port  Description
----  --------------------------------------------------------------------------
1/g36                                                                          

Flow Control:Enabled 

Thanks again for your help. 

Some update:

I am able to see the icmp traffic on the mirror destination. But still no multicast traffic.

Thanks for any help.

Hello!

Somtimes there is another TTL/hop count in the application itself.  When routing between vlans I had to increase this for it to work on another VLAN.  I used a rather larger number like 16 and it worked.  Don't know if your app has this setting, but I did see one when I setup VLC media player.     

Another thing you should probably look at is using diffserv to do this. 

Barrett, thanks for the reply. It should not be TTL in the application, since I can receive multicast on the mirror source interface. The problem is even I see multicast on the mirror source, I don't see it on mirror destination.

Thanks. However, I did set application TTL to 16, and still cannot make it work. I am using iperf for the test. The command for the multicast source:

iperf -c 239.1.1.1 -u -T 16 -t 100 -i 1

where -T 16 should set the TTL to 16. And I even cannot see any udp traffic been mirrored to the mirror destination, by using "tcpdump udp -i ethx". (ethx is the interface connects to the mirror destination interface)

Any other possible problems? Thanks.

Barrett may have a pretty good point.  If it gets to the source port then not to the destination.  Something is not keeping it alive, blocking or incorrect configuration.

Actually, it is the other way around. The client is the one sends out the multicast packets and sets the TTL, where the server just listens to the multicast group (binding to the multicast group address).

Can you suggest other tool for testing? I can give it a try. Thanks for your help.  

hmmm.  I am not too familiar with iperf, but from what I've read it seems the source (server) has the -s switch whereas the client has the -c switch.  I also read that the source must bind the multicast address using the -B switch.  So here is one example:

Source:  iperf -s -u -B 239.1.1.1  (and of cource the TTL would go here)

Client:    iperf -c -239.1.1.1 -u  

The VLC media player worked great, is free, with an easy to use gui interface.  the player is actually both the client and server.  So any Windows box I put it on could be a server or a client.  but without igmp setup properly I noticed it appeared to be multicasting as I had intended, but was actually broadcasting.  Had to bring up wireshark to see that even when I turned off the client, the packets continued to be recieved on the port.      

Some more update:

I am able to see rx_multicast increase from Ethtool's output "ethtool -S eth2 | grep multicast" on Server 3. It shows same number of multicast as Server 2. Does it mean that multicast packets have actually been mirrored to Server 3?

However, I still don't get any multicast traffic from tcpdump. Any ideas?

Thanks!