Enable IGMP Snooping while on AP mode

[flateric]

Hi everyone,

I have an Asus RT-AC1200G+ router working in AP mode which is connected to my Internet/TV provider router via the WAN port. I have a STB connected to one of the LAN ports of the Asus router.

Since there is multicast traffic reaching the Asus router (for IPTV), I would like to turn IGMP Snooping on to filter the multicast traffic on my LAN. I know that multicast traffic is not being filtered on LAN because when I switch on the STB all LAN lights start blinking like crazy, which means all ports are getting the multicast traffic.

The problem is that the Asus admin interface only allows to switch on IGMP Snooping on LAN while on router mode. But the option is not available while on AP mode.

The question is, does anyone know how to enable IGMP Snooping for LAN while on AP mode? Is there any command to do it on the command line via telnet/ssh?

Thanks.

 

[sfx2000]

IGMP snooping is a function of the switch incorporated into the Router SoC, not of the radio chips.

 

[maxbraketorque]

IGMP snooping is a function of the switch incorporated into the Router SoC, not of the radio chips.

And apparently that is handled by CPU of the main router rather than the CPU on the AP?

 

[flateric]

IGMP snooping is a function of the switch incorporated into the Router SoC, not of the radio chips.

Sorry, can you explain me better?

And apparently that is handled by CPU of the main router rather than the CPU on the AP?

If that is the case, the main router should be able to filter the multicast to some ports on the Asus router (secondary router)?

 

[sfx2000]

And apparently that is handled by CPU of the main router rather than the CPU on the AP?

You only need a single IGMP snooper - it'll take the multicast traffic and change it into unicast - and it should be on the primary router...

Since it is a routing function - routing is disabled with an Asus Router/AP in AP mode...

Some background on IGMP Snooping - Juniper says it best...

Understanding IGMP Snooping and Multicast Forwarding
IGMP snooping monitors the Internet Group Management Protocol (IGMP) traffic between hosts and multicast routers. The switch uses what IGMP snooping learns to forward multicast traffic only to interfaces that are connected to interested receivers. This conserves bandwidth by allowing the switch to send multicast traffic to only those interfaces that are connected to hosts that want to receive the traffic, instead of flooding the traffic to all interfaces in the VLAN. This topic describes how Juniper Networks EX Series Ethernet Switches forward multicast traffic when IGMP snooping is enabled.​

 

[flateric]

You only need a single IGMP snooper - it'll take the multicast traffic and change it into unicast - and it should be on the primary router...

Since it is a routing function - routing is disabled with an Asus Router/AP in AP mode...

Some background on IGMP Snooping - Juniper says it best...

Understanding IGMP Snooping and Multicast Forwarding
IGMP snooping monitors the Internet Group Management Protocol (IGMP) traffic between hosts and multicast routers. The switch uses what IGMP snooping learns to forward multicast traffic only to interfaces that are connected to interested receivers. This conserves bandwidth by allowing the switch to send multicast traffic to only those interfaces that are connected to hosts that want to receive the traffic, instead of flooding the traffic to all interfaces in the VLAN. This topic describes how Juniper Networks EX Series Ethernet Switches forward multicast traffic when IGMP snooping is enabled.​

Understood. But, if that's the case, why do I have an option to enable IGMP Snooping for the wireless network (under Wireless->Professional menu)?

 

[sfx2000]

Understood. But, if that's the case, why do I have an option to enable IGMP Snooping for the wireless network (under Wireless->Professional menu)?

Because as a consumer device - it's expected to be the first router in the chain, hence there is some benefit to having that functionality...

 

[glugglug]

It makes sense to have the option listed separately for WiFi, because sending the packets to all WiFi devices is a lot more expensive than sending it to all the wired switch ports.

This is the emf_enable setting in NVRAM. You could try logging into the access point in SSH and typing the following:

nvram set emf_enable=1
nvram commit
reboot

This may set it to do the efficient multicast forwarding even if the option isn't showing up in the UI, I don't really know.

Out of curiousity... you say you are in AP mode but your router is connected via the WAN port? I didn't know that worked. Do we effectively have 5 LAN ports on the router when in AP mode?

Another option in order to get all the other LAN tabs unhidden is to put your router back in the default "Wireless Router Mode", disable the DHCP server under the LAN->DHCP Server tab so it doesn't conflict with DHCP from your primary router, and connect via a LAN port, not the WAN port. After checking these settings on my AP mode routers I'm temped to switch to this setup myself, as there are other hidden settings which are defaulted to non-optimal values when in AP mode, for example jumbo frames are disabled, and it's more convenient to be able to change these things in the UI instead of through SSH. I can understand why the DHCP tab is hidden in access point mode but I don't get why the other tabs are hidden.

 

[flateric]

It makes sense to have the option listed separately for WiFi, because sending the packets to all WiFi devices is a lot more expensive than sending it to all the wired switch ports.

This is the emf_enable setting in NVRAM. You could try logging into the access point in SSH and typing the following:

nvram set emf_enable=1
nvram commit
reboot

This may set it to do the efficient multicast forwarding even if the option isn't showing up in the UI, I don't really know.

Thanks, I'll try the emf_enable option when I get home.

Out of curiousity... you say you are in AP mode but your router is connected via the WAN port? I didn't know that worked. Do we effectively have 5 LAN ports on the router when in AP mode?

Yes, you can use the WAN port to get the signal from the main router and have 4 ports available for LAN, while on AP mode.

Another option in order to get all the other LAN tabs unhidden is to put your router back in the default "Wireless Router Mode", disable the DHCP server under the LAN->DHCP Server tab so it doesn't conflict with DHCP from your primary router, and connect via a LAN port, not the WAN port. After checking these settings on my AP mode routers I'm temped to switch to this setup myself, as there are other hidden settings which are defaulted to non-optimal values when in AP mode, for example jumbo frames are disabled, and it's more convenient to be able to change these things in the UI instead of through SSH. I can understand why the DHCP tab is hidden in access point mode but I don't get why the other tabs are hidden.

I've already tried to revert to the default router mode as you've suggested and it works. But, using this setup, you'll only get 3 ports to connect devices, since you can't use the WAN port and one of the LAN ports.

 

[flateric]

It makes sense to have the option listed separately for WiFi, because sending the packets to all WiFi devices is a lot more expensive than sending it to all the wired switch ports.

This is the emf_enable setting in NVRAM. You could try logging into the access point in SSH and typing the following:

nvram set emf_enable=1
nvram commit
reboot

This may set it to do the efficient multicast forwarding even if the option isn't showing up in the UI, I don't really know.

Just tried it and I think it worked.

Before entering your commands, I've entered the command "nvram get emf_enable" and it was set to 0. After inputting the commands you've suggested, the get command returns 1 and the LAN lights no longer blink continuously when the STB is on!

I'll update this thread if something new comes up.

 

[flateric]

It makes sense to have the option listed separately for WiFi, because sending the packets to all WiFi devices is a lot more expensive than sending it to all the wired switch ports.

This is the emf_enable setting in NVRAM. You could try logging into the access point in SSH and typing the following:

nvram set emf_enable=1
nvram commit
reboot

This may set it to do the efficient multicast forwarding even if the option isn't showing up in the UI, I don't really know.

Good news is that this command enables the IGMP Snooping, even on AP mode. However, it does not work well on my case... the TV image freezes after a few seconds. I guess I'll have to keep it disabled.