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Community Member

Multicasting with only switches and no router

Hi,

I have an Altiris Deployment Server which is connected to a Cisco 3560 switch. The 3560 switch is connected to multiple 2950 and 2960 switches. The clients are connected to the 2950 and 2960 switches.

Because I want to deploy the same image on multiple clients in the same time I need to configure multicast routing. I don't have a router in the network. I'm a little bit confused by the explanation in the many different manuals because they al l uses a router.

Which commands do I need to let it work without a router?

Thanks in advance,

Best regards,

Ruben

1 ACCEPTED SOLUTION

Accepted Solutions
Hall of Fame Super Silver

Re: Multicasting with only switches and no router

Hello Ruben,

the only possible issue comes from IGMP snooping that is enabled by default on Cisco switches.

When a router is missing in a Vlan where IGMP snooping is active you have two options:

a) you disable igmp snooping for that vlan, multicast traffic will flow out all ports of the vlan that can span on multiple switches (you need to disable on all of them)

on all switches:

no ip igmp snooping vlan M

b) if supported only one device has to act as IGMP snooping querier : that is it has to send periodic IGMP queries so that all switches can build a table that says what users have interest in receiving group G1, what users want to receive group G2 and so on.

C3560 supports it.

see

https://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_44_se/configuration/guide/swigmp.html#wp1055584

int vlan M

ip address x.y.z.k

no shut

exit

ip igmp snooping querier x.y.z.k

where M is the vlan of interest, x.y.z.k is an ip address of the IP subnet used in vlan M that the switch will use as source of IGMP queries.

Hope to help

Giuseppe

4 REPLIES

Re: Multicasting with only switches and no router

Hello Ruben.

If you are just switching and all devices are in the same IP subnet then you need NO configuration to make it work. Multicast traffic will be flooded to all hosts that request it.

Simon

Hall of Fame Super Silver

Re: Multicasting with only switches and no router

Hello Ruben,

the only possible issue comes from IGMP snooping that is enabled by default on Cisco switches.

When a router is missing in a Vlan where IGMP snooping is active you have two options:

a) you disable igmp snooping for that vlan, multicast traffic will flow out all ports of the vlan that can span on multiple switches (you need to disable on all of them)

on all switches:

no ip igmp snooping vlan M

b) if supported only one device has to act as IGMP snooping querier : that is it has to send periodic IGMP queries so that all switches can build a table that says what users have interest in receiving group G1, what users want to receive group G2 and so on.

C3560 supports it.

see

https://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_44_se/configuration/guide/swigmp.html#wp1055584

int vlan M

ip address x.y.z.k

no shut

exit

ip igmp snooping querier x.y.z.k

where M is the vlan of interest, x.y.z.k is an ip address of the IP subnet used in vlan M that the switch will use as source of IGMP queries.

Hope to help

Giuseppe

Community Member

Re: Multicasting with only switches and no router

Thank you, I've entered the commands and will test it next monday or tuesday.

Super Bronze

Re: Multicasting with only switches and no router

"Which commands do I need to let it work without a router? "

BTW, if you're not aware, your 3560 is a L3 switch which means it can route. If it were doing so, it also supports multicast routing.

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