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Multicast on Cisco network

Posted on 2007-10-18
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I have a Cisco network which consists of 2 core 6513 switches which feed about 20 edge switches which are Cisco 3550 and 3750s. Vlan 1 is for management and vlan 10 is where the network peripherals are attached to. We are doing a mass rollout and require multicast enabling throughout the network so we can ghost the PCS from the users desk. Any help appreciated.
Ip multicast routing is enabled on the 2 catalyst Cisco 6513s. Where else do I put the commands
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Question by:andrewwismith
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by:Freya28
ID: 20100464
this is a pretty good document to look through.  try it out and see if it is what you need

http://www.cisco.com/en/US/docs/ios/12_0/np1/configuration/guide/1cmulti.html
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Don Johnston earned 2000 total points
ID: 20100504
First off, multicast is one of those things where there are many variables and numerous ways to implement it.

That said, it sounds like everything is already on VLAN 10. Why not put the server on VLAN 10 and that way you don't have to worry about multicasting?

If you must multicast, the easiest config would be:

ip multicast-routing
 int vlan x                    \
 ip pim dense-mode    /  Repeat for each interface that is sending/receiving multicast on each switch


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by:andrewwismith
ID: 20100819
I am confused surely you still configure multicast even though you are on the same vlan
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by:Don Johnston
ID: 20100849
No.

If you're on the same VLAN, you're on the same broadcast domain. Switches treat multicast and broadcast traffic the same. They are both flooded out all ports in the same VLAN.

That's why it's called multicast ROUTING.

You only need a router if you're going from one VLAN to another (different) VLAN.
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Author Comment

by:andrewwismith
ID: 20100962
Fair point. The people here doing the rollout insist unless multicast is enabled they can't continue as it is too slow.
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by:andrewwismith
ID: 20101002
Symantec Ghost minimizes its effect on network traffic by using multicasting, which sends out the image once for many computers rather than resending the image for each client computer.

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by:Don Johnston
ID: 20101080
>The people here doing the rollout insist unless multicast is enabled they can't continue as it is too slow.

Something fishy here. If the server and clients are not on the same broadcast domain, multicast MUST be enabled. They're saying that if it's not enabled that it will be too SLOW?
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by:andrewwismith
ID: 20101113
They are on the same broadcast domain.
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by:Don Johnston
ID: 20101161
Then there is absolutely no need to enable multicast routing. If it were enabled, there would be no effect on the operation.
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by:andrewwismith
ID: 20107400
As multicast is still not working we can only unicast. If we disabled the IGMP snooping on the switches would multicast traffic flood out each port. Would this have an impact on the network?
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by:Don Johnston
ID: 20107939
Then something else is causing the problem. IGMP snooping is disabled by default. Which means that multicast traffic is flooded. All IGMP snooping does is limit which ports the multicast is flooded out.
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by:andrewwismith
ID: 20108001
IGMP snooping is enabled by default on  Cisco 3750 and 3550 switches

Switch#sh ip igmp snooping
Global IGMP Snooping configuration:
-----------------------------------
IGMP snooping              : Enabled
IGMPv3 snooping (minimal)  : Enabled
Report suppression         : Enabled
TCN solicit query          : Disabled
TCN flood query count      : 2
Last member query interval : 1000

Vlan 1:
--------
IGMP snooping                       : Enabled
Immediate leave                     : Disabled
Multicast router learning mode      : pim-dvmrp
Source only learning age timer      : 10
Last member query interval          : 1000
CGMP interoperability mode          : IGMP_ONLY

Vlan 2:
--------
IGMP snooping                       : Enabled
Immediate leave                     : Disabled
Multicast router learning mode      : pim-dvmrp
Source only learning age timer      : 10
Last member query interval          : 1000
CGMP interoperability mode          : IGMP_ONLY

Vlan 10:
--------
IGMP snooping                       : Enabled
Immediate leave                     : Disabled
Multicast router learning mode      : pim-dvmrp
Source only learning age timer      : 10
Last member query interval          : 1000
CGMP interoperability mode          : IGMP_ONLY

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by:Don Johnston
ID: 20108009
I did not know that... Learn something new everyday.

Still doesn't explain why ghost isn't working though.
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by:andrewwismith
ID: 20108046
It works as unicast. We can set up to about 8 unicast sessions at once.
But we want to set it up to multicast as one to many.
I am going to disable IGMP snooping on one of the switches and try that.
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Author Comment

by:andrewwismith
ID: 20146542
It only needed configuring on one of the cisco 6513s
I issued Ip PIm dense mode on int vlan 10 and it did not work but when i issued the IP PIM sparse mode it worked.
Nothing needed to be configured on any of the edge switches as IGMP snooping is on by default
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