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IGMP SNOOPING and PIM-DVMRP

miquelsayeras
Level 1
Level 1

‎08-20-2003 09:11 AM - edited ‎03-02-2019 09:45 AM

I'm training with two 3550 switches and ip multicast-routing. These switches are interconnected with both gigabith 0/1 port.

I started this switches with default configuration, I assign every switch IP address 192.168.0.10 and 192.168.1.10 on the interface vlan 1, and configure IGMP snooping.

My problem apears when I send multicast traffic from switch 1 without any multicast membership, no fastethernet port receives trafic but de gi0/1 of second switch receive all multicast paquets. I activate pim-sm protocol but my problem persist, what I make bad?

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8 Replies 8

seilsz
Level 4
Level 4

‎08-20-2003 10:34 AM

miquelsayeras -

Can you send the output from the following command:

sh ip igmp snooping

After you send multicast traffic, capture the output from the following command:

show mac-address-table multicast

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miquelsayeras
Level 1
Level 1
In response to seilsz

‎08-20-2003 10:18 PM

The igmp configuration is:

switch1#sh ip igmp snooping

vlan 1

----------

IGMP snooping is globally enabled

IGMP snooping is enabled on this Vlan

IGMP snooping immediate-leave is disabled on this Vlan

IGMP snooping mrouter learn mode is pim-dvmrp on this Vlan

IGMP snooping is running in IGMP_ONLY mode on this Vlan

switch2#show ip igmp snooping

vlan 1

----------

IGMP snooping is globally enabled

IGMP snooping is enabled on this Vlan

IGMP snooping immediate-leave is disabled on this Vlan

IGMP snooping mrouter learn mode is pim-dvmrp on this Vlan

IGMP snooping is running in IGMP_ONLY mode on this Vlan

BEFORE SEND MTRAFIC:

switch1#show mac address-table multicast

Vlan Mac Address Type Ports

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

switch2#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0128 IGMP Gi0/1

AFTER SEND MTRAFIC IN SWITCH 1 FASTETHERNET PORT 2

switch1#show mac address-table multicast

Vlan Mac Address Type Ports

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

switch2#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0128 IGMP Gi0/1

I START RECEIVE FROM SAME PORT

switch1#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0101 IGMP Fa0/2, Gi0/1

switch2#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0101 IGMP Gi0/1

1 0100.5e00.0128 IGMP Gi0/1

Thanks in advance,

Miquel

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seilsz
Level 4
Level 4
In response to miquelsayeras

‎08-21-2003 02:31 AM

Miquel,

I believe this behavior is caused by the fact that routers must receive all multicast traffic for all groups. Since the 3550 is essentially functioning as an IOS router, multicast traffic is always forwarded on the interface connecting to the other 3550 (Gi0/1).

Can you try the same test but locate the multicast sending in switch 2?

~Zach

miquelsayeras
Level 1
Level 1
In response to seilsz

‎08-21-2003 02:56 AM

BEFORE SENDING MTRAFIC

switch1#show mac address-table multicast

Vlan Mac Address Type Ports

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

switch2#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0128 IGMP Gi0/1

AFTER SEND MTRAFIC IN SWITCH 2 FASTETHERNET PORT 1

switch1#show mac address-table multicast

Vlan Mac Address Type Ports

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

switch2#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0128 IGMP Gi0/1

AFTER START RECEIVE MTRAFIC IN SWITCH 1 FASTETHERNET PORT 2

switch1#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0101 IGMP Fa0/2, Gi0/1

1 0100.5e00.0128 IGMP Gi0/1

switch2#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0101 IGMP Gi0/1

IF I START RECIVE MTRAFIC IN SWITCH 2 FASTETHERNET PORT 1

switch1#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0101 IGMP Fa0/2, Gi0/1

1 0100.5e00.0128 IGMP Gi0/1

switch2#show mac address-table multicast

Vlan Mac Address Type Ports

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

1 0100.5e00.0101 IGMP Fa0/1, Gi0/1

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miquelsayeras
Level 1
Level 1
In response to miquelsayeras

‎08-25-2003 11:34 PM

On the third post you say: "I believe this behavior is caused by the fact that routers must receive all multicast traffic for all groups. Since the 3550 is essentially functioning as an IOS router, multicast traffic is always forwarded on the interface connecting to the other 3550 (Gi0/1). ".

I think it's no really true, I was reading "Catalyst 3550 Multilayer Switch Software

Configuration Guide". On chapter 33 page 5 they explain PIM DM protocol, and say "If a PIM DM device receives a multicast packet and has

no directly connected members or PIM neighbors present, a prune message is sent back to the source.

Subsequent multicast packets are not flooded to this router or switch on this pruned branch.", therefore I enable PIM protocol.

It's possible that made a bad PIM configuration? I only do the steps "configuring Basic Multicast Routing" on chapter 33 page 15.

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miquelsayeras
Level 1
Level 1
In response to miquelsayeras

‎08-25-2003 11:35 PM

On the third post you say: "I believe this behavior is caused by the fact that routers must receive all multicast traffic for all groups. Since the 3550 is essentially functioning as an IOS router, multicast traffic is always forwarded on the interface connecting to the other 3550 (Gi0/1). ".

I think it's no really true, I was reading "Catalyst 3550 Multilayer Switch Software

Configuration Guide". On chapter 33 page 5 they explain PIM DM protocol, and say "If a PIM DM device receives a multicast packet and has

no directly connected members or PIM neighbors present, a prune message is sent back to the source.

Subsequent multicast packets are not flooded to this router or switch on this pruned branch.", therefore I enable PIM protocol.

It's possible that made a bad PIM configuration? I only do the steps "configuring Basic Multicast Routing" on chapter 33 page 15.

Thanks in advance,

Miquel

0 Helpful

seilsz
Level 4
Level 4
In response to miquelsayeras

‎08-26-2003 09:40 PM

Miquel,

From a layer 3 perspective, you are correct. A PIM-DM router without directly connected members or PIM neighbors will send a prune message towards the source. However, we are talking about IGMP snooping, which is trying to deal with multicast traffic at layer 2. When the IGMP snooping function sees PIM packets from an interface, it makes the assumption that a router is connected to that port and forwards all multicast traffic to that interface.

I have a couple of 3550's in the lab. Let me validate that what I'm saying and post the results here.

~Zach

0 Helpful

miquelsayeras
Level 1
Level 1
In response to seilsz

‎08-27-2003 09:51 AM

Tank you for your interest, your words let me understand the problem.

My ininitial goal was to configure the switch to prune all interfaces that are not subscribed on a multicast group, for this reason I try to configure IGMP snooping with PIM, but these seems to be a bad idea.

There is any possible solution to solve my problem?

Miquel.

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