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ip igmp snooping querier?

Hi

i've been reading these forums and noticed that lot of people have problems with configuring multicast. basicly, problems are flooding bandwidth, no querier, confusing pim router configuration ...

also, ive seen some promisses from tehnical stuff that next gen of linksys switches will have #ip igmp snooping querier, like cat ones have. so i'm interested if someone can give me the answer.

it is interesting question for many people who would cant afford expensive cat switches for such simple usage.

regards,

david

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Hi david,

Chapter 14 of the 300 series Admin guide states the following;

"The Sx300 can be configured to be an IGMP Querier as a backup querier, or in

situation where a regular IGMP Querier does not exist. The Sx300 is not a full

capability IGMP Querier.

If the switch is enabled as a IGMP Querier, it starts after 60 seconds have passed

with no IGMP traffic (queries) detected from a Multicast router. In the presence of

other IGMP Queriers, the switch might (or might not) stop sending queries, based

on the results of the standard querier selection process."

Hope this answers your question.

regards Dave

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Thanks for quick reply!

How is it possible that I have SRW224G4P model and I can't enable ip igmp quering?

I only have option to enable igmp snooping.

Regards,

David

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Hi David,

The new 300 series version SRW224G4P-K9-NA  is generations ahead of the older sibling SRW224G4P .

You actually have a lot more options as seen in the GUI, so I though I would put as simple network together and run you through a validation.

Here is a simple network diagram I put together showing my simple network topology;

I chose the RV042 in this network to provide DHCP services, but shortly after all devices had IP addresses removed the RV042 becauise I noticed it was sending out IP IGMP general queries. 

diag.jpg

I am using a software based multicast tester that sits on the PC.  It can either send and/or receive multicasts of a defined group and responds appropriately to IGMP General queries. I will call this software MCT (Multicast test).

I had the MCT software on PC C.  PC C is plugged into switch port 10  It is sending multicasts into the switch at a rate of about 10 multicast packets a second.

I had the MCT software on PC A. PC A  is plugged into switch port  1.  It is set to receiving and count multicasts from the switch

I had PC B plugged into switch port 2. PC B is  checking switch statistics, but not try to receive multicasts from PC 3.

I had setup multicast snooping on VLAN 1 and querying according to the GUI screen capture below.

Note: I only had a single vlan on this switch.

querier setup.jpg

In a composite of two screen captures below,  you can see that IGMP querier status is enabled.

querier1.jpg

I took off the RV042 out of the network, because i noticed within a wireshark capture on PC A,   that the RV042 was sending out group general queries.  I wanted the switch to take over that role

I waited a few minutes,  and displayed only igmp activity.

It can be  clearly seen in the screen capture  below;

  • SG300 series switch was sending out general queries (2 minutes) from source IP address 172.16.1.100.
  • It waited for the mcast router general query, but when none came,  60 seconds later sent out it's own general query.  Fair enough, it had to assume a mcast router might be sending general queries every minute.

querier2.jpg

Switch statistics can be seen below,  it showed;

  • that PC B on switch port G2 was not being flooded by multicasts, in other words snooping is working;
  • Port 10,  PC C is sending in 2962  multicast packets to the switch.
  • Port 1,   PC A  is receiving 2900 multicast packets from the switch
  • port 2 ,   PC B is not part of the multicast group 234.55.66.77 and as such is not being flooded by multicasts.

ALL three PCs are windows based products,  and certain multicasts emanate from these devices.

show interafce count

      Port       InUcastPkts  InMcastPkts  InBcastPkts    InOctets 

---------------- ------------ ------------ ------------ ------------

      gi1             12           9            6           3493    

      gi2            247          237           6          43733    

      gi3             0            0            0            0      

      gi4             0            0            0            0      

      gi5             0            0            0            0      

      gi6             0            0            0            0      

      gi7             0            0            0            0      

      gi8             0            0            0            0      

      gi9             0            0            0            0      

      gi10            26          2962          3          850881   

      gi11            0            0            0            0      

      gi12            0            0            0            0      

      gi13            0            0            0            0      

      gi14            0            0            0            0      

      gi15            0            0            0            0      

      gi16            0            0            0            0      

      gi17            0            0            0            0      

      gi18            0            0            0            0      

      gi19            0            0            0            0      

      gi20            0            0            0            0      

      gi21            0            0            0            0     

      gi22            0            0            0            0      

      gi23            0            0            0            0      

      gi24            0            0            0            0      

      gi25            0            0            0            0      

      gi26            0            0            0            0      

      gi27            0            0            0            0      

      gi28            0            0            0            0      

      Port       OutUcastPkts OutMcastPkts OutBcastPkts  OutOctets  

---------------- ------------ ------------ ------------ ------------

      gi1             13         2900          9          839691   

      gi2            233         343           9          90453    

      gi3             0            0            0            0      

      gi4             0            0            0            0      

      gi5             0            0            0            0      

      gi6             0            0            0            0      

      gi7             0            0            0            0      

      gi8             0            0            0            0      

      gi9             0            0            0            0      

      gi10            24          343           12         47165    

      gi11            0            0            0            0      

      gi12            0            0            0            0     

      gi13            0            0            0            0      

      gi14            0            0            0            0      

      gi15            0            0            0            0      

      gi16            0            0            0            0      

      gi17            0            0            0            0      

      gi18            0            0            0            0      

      gi19            0            0            0            0      

      gi20            0            0            0            0      

      gi21            0            0            0            0      

      gi22            0            0            0            0      

      gi23            0            0            0            0      

      gi24            0            0            0            0      

      gi25            0            0            0            0      

      gi26            0            0            0            0      

      gi27            0            0            0            0      

      gi28            0            0            0            0

If I look at the multicast groups within the switch, it show that only two ports were involved in multicast group 234.55.66.77;


switch4cf17c#sh ip igmp snooping group

Vlan   Group        Source        Include Ports        Exclude Ports     Comp.

       Address      Address                                              Mode 

---- ------------ ------------ -------------------- -------------------- -----

1    234.55.66.77 *            gi1,gi10                                  v2   

1    239.255.255. *            gi1-2,gi10                                v2   

     250                                                                      

Just to complete the posting, here is the CLI command (highlighted)  to enable the querier functionality within the switch;

[Kswitch4cf17c#sh run

bridge multicast filtering

ip igmp snooping

ip igmp snooping vlan 1

ip igmp snooping vlan 1 querier

interface vlan 1

ip address 172.16.1.100 255.255.255.0

exit

interface vlan 1

no ip address dhcp

exit

hostname switch4cf17c

no passwords complexity enable

no snmp-server server

ip telnet server

Hope this helps you and others

regards Dave


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