multicasting scope value

hclisschennai · ‎06-28-2009

Hi,

Can anyone help me in how to decide the multicast scope. Putting it in simple way I have 4 Routers R1--R2--R3--R4. R1 is configured as RP and I need to configure scope in such a way that Multicasting doesnot forward after R4.

Whether I have to configure R1 with scope as 3 (with calculation of R2,R3 & R4 as 3 Hops) or scope as 4 (with calculation of R1,R2,R3 & R4 as 4 Hops)

Thanks in advance,

RBK

Istvan_Rabai · ‎06-28-2009

Hi RBK,

If the multicast traffic is originated by R1 on its interface to R2, then the TTL should be 3.

If the multicast traffic is originated on another interface of R1 (e.g. on its loopback interface for AutoRP announcements) then you have to set the TTL to 4.

If the multicast traffic is originated on a host that is connected to R1 then again the TTL should be set to 4.

Cheers:

Istvan

Laurent Aubert · ‎06-28-2009

Hi RBK,

Another solution is to use multicast boundary feature on R4 so you don't need to worry about scope anymore:

http://www.cisco.com/en/US/docs/ios/12_2/ipmulti/command/reference/1rfmult1.html#wp1058494

HTH

Laurent.