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Multicast assignment question

CiscoPurpleBelt
Frequent Contributor
Frequent Contributor

So if I need to reserve a multicast space let's say to be used for video monitors or something, what would be the best range to use as I know many 224.0.0.X are used for certain protocol comms. Any help guys?

1 Accepted Solution

Accepted Solutions

That is correct. 1 ip address (i.e. 239.0.0.1) = 1 ip multicast group.

 

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

View solution in original post

14 Replies 14

Harold Ritter
Cisco Employee
Cisco Employee

Please refer to the following white paper.

 

https://www.cisco.com/c/dam/en/us/support/docs/ip/ip-multicast/ipmlt_wp.pdf

 

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

I am getting a not found error

Thanks buddy!

 

I am no expert at understanding all this but looks like 239.000.000.000-239.191.255.255 would be a good range to use.

Basically, each group of hosts would be pointing to let's say 239.0.0.1 meaning I have plenty of address space to use for groups of hosts that require multicast correct?

Is it best to limit the number of host pointing to a particular multicast IP to let's say under 254?

Sorry for the wrong URL. I posted from my phone ;-) I corrected the link. Thanks to Jon as well for sending the proper link.

 

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

I am no expert at understanding all this but looks like 239.000.000.000-239.191.255.255 would be a good range to use.

Basically, each group of hosts would be pointing to let's say 239.0.0.1 meaning I have plenty of address space to use for groups of hosts that require multicast correct?

Is it best to limit the number of host pointing to a particular multicast IP to let's say under 254?

Yes, the block you mentioned should be plenty of space, even for a large enterprise network.

 

You normally assign 1 multicast group per multicast stream, not per group of hosst. So all hosts interested to a specific stream will request their interest for that group via IGMP for ipv4 or MLD for ipv6.

 

There are no hard limit to the number of hosts that can join a multicast group. In principal the more hosts you have the more efficient multicast is versus unicast.

 

Regards

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Hey thanks!

So any host requesting the multicast stream would need to be configured accordingly and the router would dynamically assign any address in that range?

The multicast source, the application streaming the video for instance, would be configured to stream the information using a specific multicast group address. The receivers, the hosts interested in that multicast stream, could be statically configured or could receive the multicast group information out of band. These hosts would in turn signal their desire to join the specific multicast group to the directly connected router using IGMP or MLD as I mentioned previously.

 

Regards,

 

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Awesome!

In general, is the multicast group address usually 1 ip (e.g. 239.0.0.1) for a group?

I am just trying to figure out how many IPs I would have available for groups in the 239 address space.

That is correct. 1 ip address (i.e. 239.0.0.1) = 1 ip multicast group.

 

Regards,

Harold Ritter
Sr Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México
Paseo de la Reforma 222
Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México

Ok would it be wise/best practice to have 239.0.0.1 as group 1 multicast ip, 239.0.0.2 as second group, etc.?

It makes sense if you can organize them that way.  It also helps during troubleshooting.

HTH

For the pim rp-address, I was thinking of using let's say a 1.1.1.1 address to make things simple and unique from other subnet addresses. Would you say this is a good practice or better to use let's say 10.0.1.1?

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