ip igmp snooping querier?

[10robinho]

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

[David Hornstein]

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

[10robinho]

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

[David Hornstein · Accepted solution]

Hi David,

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.

But I am assuming you have the refreshed version of the SRW224G4P switch called the SRW224G4P-K9-NA .

If you have the old switch the following is not relevant to you.

I put together a simple network diagram showing my simple network topology used during my wee test;

I chose the RV042 as my Layer 3 router  in this network.  

It really was to provide DHCP services, but shortly after all devices had IP addresses, I removed the RV042,  becauise I noticed it was sending out IP IGMP general queries.     Something I didn;t want in the following test.

I was using a software based multicast tester, produced by the wonderful folk at Twisted Pair Solutions.  This software 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.

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

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.

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.  This is the correct behaviour.

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

[10robinho]

Mr Dave,

thank you very much for this detailed explanation. I'm realy network beginner but I've understanded everything.

Unfortunately, I have the old version of switch, but after this plesant experience width cisco support I'm sure I will buy new switch for my multicast.

What are your recommendations if it would be used for 24/7 video multicasting? Are these SX 300 good enough?

Regards,

David

[David Hornstein]

Hi David

Thank you very much for your kind words.

The 300 series switch are in fact a new technology, as you can see from the screen captures, generation ahead of your old switch.

I have no issues with the SG300 or SF300 series switches (refresh on the older SRW series), and have the free use of using a SG300-10P (SRW2008P-K9-NA) at home even though I have access to higher end switches,

But to better answer your question,  I would like to know;

• Do you need fanless operation ?
• how many ports do you require?
• Are 100M ports sufficient or do you need GbE on access ports?
• The environment of the switch, hot cold, enclosed, open area, humid, dry?

They are of course not as flexible compared to the catalyst big brothers, but never the less,  are great small business switches and are at a  darn good price.

The 300 series switches come with tremendous warranty and NBD replacement, but to give you a recommendation as to a specific model, it would be interesting to answers to the questions above. 

If you want to compare switches yourself check out the following URL.

http://www.cisco.com/en/US/products/ps10898/prod_models_comparison.html

The datasheet will give you details on fan or 11 fanless models within the protfolio.

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps10898/data_sheet_c78-610061.html
.

You can email me at dhornste at cisco.com  ( remove spaces on either side of the at and replace it with @ )  with a contact phone number, I am happy to give you a quick call to discuss.

regards Dave

[10robinho]

Mr Dave,

I've bought a new SF 300-24.

I havent config anything except switch ip address.

When I run my multicast stream I got flooding.

Then, I've turned igmp snooping and quering on at vlan 1 (default) but nothing happened, floooding was still present.

Then, I've set up unregistred multicast to "filtering" on all ports.

After that, I've managed to get multicast working.

But, when I disable igmp querier, nothing happen, multicast is still working.

This is confusing me now, I tought that I need querier for multicast to work propretly.

Am I missing something?

Regards,

David

[David Hornstein]

Hi David,

In a past job, where i helped configure the triple play which was;

• voice
  
• IP multicast video
  
• data
  
• 
  

In those networks I must admit we had Layer 3 switches running PIM DM, IGMP and snooping, so we had a Layer 3 querier for the sake of multicast IP video.

If you have a concern about understanding IGMP snooping, there is a brief, but good tutorial on IGMP snooping, at the following URL;

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SXF/native/configuration/guide/snooigmp.html#wp1052493

A excerpt states "You can configure the switch to use IGMP snooping in subnets that receive IGMP queries from either IGMP or the IGMP snooping querier."

Dare I suggest, a simpler explaination from the following source says "In order for IGMP, and thus IGMP snooping, to function, a multicast router must exist on the network and generate IGMP queries." http://en.wikipedia.org/wiki/IGMP_snooping

The implication is you must really have some sort of Layer 3 querier on the network, for snooping to work effectively..

Without a querier or igmp snooping enabled, i would fully expect multicast to flood all ports.

I would have thought that my CLI script above would have stopped the flooding.

If you are still concerned, ring up the Small Busienss Support Center (SBSC) at the following URL and show them this posting.

http://www.cisco.com/en/US/support/tsd_cisco_small_business_support_center_contacts.html

regards Dave

[10robinho]

Hi Dave,

It seam that it was my mistake, because igmp querier needs some time to turn on and off.

I think I got the point, thank you!

Regards,

David