Wired Intelligent Edge

Hello all,

While checking another things from inet my eyes catched next line from page Considerations when configuring IGMP  about AOS-CX IGMP considerations:

"Multicast traffic will be flooded on the VLAN, if TTL=1 or TTL>255 regardless of IGMP joins and group membership within the VLAN."

I'm 99% sure that this is not true (Dante audio signals has TTL=1 and one of my client runs well over 200 channels of audio and no 340mbps streams onsight there..)
Is there certain situations where this statement is true?

Hello all,

While checking another things from inet my eyes catched next line from page Considerations when configuring IGMP  about AOS-CX IGMP considerations:

"Multicast traffic will be flooded on the VLAN, if TTL=1 or TTL>255 regardless of IGMP joins and group membership within the VLAN."

I'm 99% sure that this is not true (Dante audio signals has TTL=1 and one of my client runs well over 200 channels of audio and no 340mbps streams onsight there..)
Is there certain situations where this statement is true?

------------------------------
Jori Luoto
AV-IT Specialist
------------------------------

TTL=1 means process but do not forward/route on the network layer. Casting that packet on the current L2 segment/VLAN (data link layer) is correct processing, just don't route it anywhere else. E.g. if you originate a multicast packet with TTL=1 that means "multicast in the current segment only, do not route".

TTL>255 must be a typo as the largest possible value for an 8-bit field is 255.

Original Message:
Sent: Nov 13, 2023 07:59 AM
From: JL24
Subject: IGMP Snooping defective if TTL=1 or TTL>255 in packet :O

Hello all,

While checking another things from inet my eyes catched next line from page Considerations when configuring IGMP  about AOS-CX IGMP considerations:

"Multicast traffic will be flooded on the VLAN, if TTL=1 or TTL>255 regardless of IGMP joins and group membership within the VLAN."

I'm 99% sure that this is not true (Dante audio signals has TTL=1 and one of my client runs well over 200 channels of audio and no 340mbps streams onsight there..)
Is there certain situations where this statement is true?

------------------------------
Jori Luoto
AV-IT Specialist
------------------------------

Hello,

Flooding means for me that multicast is converted to broadcast just like there is no igmp processing there at all. Document gives information that if mc packet's ttl is 1 or over (or equal) 255 then igmp snoping process is overrided and packet will be broadcasted into all L2 targets available.
I will open tac for this one to atleast clarify text there in document. 

TTL=1 means process but do not forward/route on the network layer. Casting that packet on the current L2 segment/VLAN (data link layer) is correct processing, just don't route it anywhere else. E.g. if you originate a multicast packet with TTL=1 that means "multicast in the current segment only, do not route".

TTL>255 must be a typo as the largest possible value for an 8-bit field is 255.

Original Message:
Sent: Nov 13, 2023 07:59 AM
From: JL24
Subject: IGMP Snooping defective if TTL=1 or TTL>255 in packet :O

Hello all,

While checking another things from inet my eyes catched next line from page Considerations when configuring IGMP  about AOS-CX IGMP considerations:

"Multicast traffic will be flooded on the VLAN, if TTL=1 or TTL>255 regardless of IGMP joins and group membership within the VLAN."

I'm 99% sure that this is not true (Dante audio signals has TTL=1 and one of my client runs well over 200 channels of audio and no 340mbps streams onsight there..)
Is there certain situations where this statement is true?

------------------------------
Jori Luoto
AV-IT Specialist
------------------------------

Well it seems to be quite hard to open case to TAC about documentation which has no serial number... 

Hello,

Flooding means for me that multicast is converted to broadcast just like there is no igmp processing there at all. Document gives information that if mc packet's ttl is 1 or over (or equal) 255 then igmp snoping process is overrided and packet will be broadcasted into all L2 targets available.
I will open tac for this one to atleast clarify text there in document. 

TTL=1 means process but do not forward/route on the network layer. Casting that packet on the current L2 segment/VLAN (data link layer) is correct processing, just don't route it anywhere else. E.g. if you originate a multicast packet with TTL=1 that means "multicast in the current segment only, do not route".

TTL>255 must be a typo as the largest possible value for an 8-bit field is 255.

Original Message:
Sent: Nov 13, 2023 07:59 AM
From: JL24
Subject: IGMP Snooping defective if TTL=1 or TTL>255 in packet :O

Hello all,

While checking another things from inet my eyes catched next line from page Considerations when configuring IGMP  about AOS-CX IGMP considerations:

"Multicast traffic will be flooded on the VLAN, if TTL=1 or TTL>255 regardless of IGMP joins and group membership within the VLAN."

I'm 99% sure that this is not true (Dante audio signals has TTL=1 and one of my client runs well over 200 channels of audio and no 340mbps streams onsight there..)
Is there certain situations where this statement is true?

------------------------------
Jori Luoto
AV-IT Specialist
------------------------------