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Problem about IGMP querier on multicast router

 
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DavidChoi
Occasional Visitor

Problem about IGMP querier on multicast router

Hi, hope any guys can help me solve the problem, thanks.

I am using a cisco 2821 for multcast routing, pim dense mode was enabled. Currently there is another core switch (procurve 5412) with the lowest IP address acting igmp querier (no ip multicast routing & no ip pim). I know that querier with the lowest IP address could win the querier election in the same vlan/subnet, but when I connect the 2821 to the same vlan as the core switch. the 2821 win the querier election. It's not the lowest IP address. Why it can win? It confuse me a lot.
9 REPLIES 9
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Matt79
Advisor

Re: Problem about IGMP querier on multicast router

Hi David,

I'm not actually familiar with the 2821 or IGMP querying in general, but usually the ProCurve products elect root devices (for Spanning Tree etc) based on the lowest MAC Address - not lowest IP Address.

Kind regards,
Matt
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Kevin Richter_1
Valued Contributor

Re: Problem about IGMP querier on multicast router

The IGMP querier function is enabled by default on the ProCurve switches when IGMP is enabled in a vlan. There are procedures for it to back off and NOT be querier when another querier is already present.

If you want to force the situation, it is quite simple. The IGMP chapter of the Multicast and Routing Guide for the 5400 (link to chapter is http://cdn.procurve.com/training/Manuals/3500-5400-6200-8200-MRG-Jan08-2-IGMP.pdf) gives the following syntax to disable the querier on a given vlan ID (vid):

no vlan ip igmp querier

The manual suggests not disabling the querier as it should be backing off automatically in the presence of a multicast router sending queries and asserting itself as querier.
Check the cabling. Next, check the cabling again.
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Matt Hobbs
Honored Contributor

Re: Problem about IGMP querier on multicast router

If you enable PIM on the 5400 it will definitely take over as multicast router on that VLAN if it has the lowest IP address. When only IGMP is enabled, it's a lot more passive.
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abdullah.ali
Occasional Advisor

Re: Problem about IGMP querier on multicast router

Hi All,

concearning the election process, does the criteria change when the pim is enabled or disabled?

does the switch with the pim and multicast routing enabled on it has the highest priority to be a querier?
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DavidChoi
Occasional Visitor

Re: Problem about IGMP querier on multicast router

Yes, I know the querier function can be disabled on procurve switch by running the command "no ip igmp querier". But seems no way to disable the querier function on cisco 2821...

After my test, I think I need to enable "ip multicast routing", "router pim" and "ip pim-dense" (suppose dense-mode is using on the vlan) on 5412, then the 5412 can sure to win the querier election.

But I want my 2821 to be the DR so that it can handle the mroute table and multicast routing traffic but not the 5412. If I enable pim-dense on the 5412, will it increase the additional workload on 5412??? such as learning the mroute table. That is what I really concern.

Thank you all for your help:)
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KenLeung
Occasional Visitor

Re: Problem about IGMP querier on multicast router

I have a similar case.
There is an HP5300 that has STP enabled, routing disabled, and it is an IGMP Querier.
And a HP3500 enabled with STP disabled, multicast routing and PIM dense mode enabled, and has implemented "no ip igmp querier".
When connecting the 3500 to 5300, sometime the 3500 will win the Querier, some time the 5300 wins.
My question is why the 3500 still win Querier even it is "no ip igmp querier"?

Then try to enable the routing, multicast routing and PIM mode on 5300, and configure with a lower IP. the 5300 always win the Querier.

Then try to configure the 5300 with higher IP, then 3500 win the Querier.

I am still testing for more cases, but it seems the command "no ip igmp querier" is ignored by some other command/function, do anyone has experienced about that?



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Mark Landry
Occasional Visitor

Re: Problem about IGMP querier on multicast router

I too had the same problem, but with slightly different kit list:-

HP 8212zl IGMP (No querier) + PIM-DM - X.X.X.1
HP 2650 IGMP (the origianl querier) - X.X.X.36

8212 insisted on becoming the querier when IGMP enabled for the Vlan....AND PIM-DM on the same Vlan even though I had specified...."no vlan 3 ip igmp querier".

Raised IP address from X.X.X.1 to X.X.X.100

Problem solved...."stream away"
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Shadow13
Respected Contributor

Re: Problem about IGMP querier on multicast router

hi,


Here are some notes about IGMP in ProCurve switches:
-A ProCurve switch can become a Querier for vlan if it has ip address in that vlan.

-If a multicast router is present, it becomes the Querier, means the router becomes Querier not the switch. (That's why when you connect the 2811 it wins the election)

-Commmand #no ip igmp querier
should be configured under the vlan that has an ip address and in which you don't want the swtich to become the Querier.


from that, you can simply remove the ip address (if available) from the vlan in order to prevent the switch from becoming the Querier.

That's all the info i have right now, if you need anything else just ask.


Regards,
Islam Hassan
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sonerk
Occasional Visitor

Re: Problem about IGMP querier on multicast router

Hi,

I have the similar problem but it is a bit different. I don't see any query number when I write "sh ip igm vl 1" command. I see Active Group Address, Ports and Reports  but Queries is zero. In log messages I see

igmp: VID 1: End Querier role
igmp: VID 1: Other Querier detected
igmp: VID 1: Querier Election in progress, addr

I use HP 2620-48 switch on the end user side. On the other hand, When I see query numbers except zero on another switch or another vlan , everything seems ok.