Simrad NSS and the WiFi-1 in detail

by Adrian on December 20, 2012

Whilst testing the NSS and GoFree interconnectivity on our boat in the real world I quickly discovered the one flaw with connecting it into your normal ship’s router and wifi access point.

You need to make sure your wifi router can support disabling IGMP multicast packets. The wifi1 does this as standard, since Navico’s radar and sonar devices flood the network with multicast packets, which ordinarily kills LAN ip traffic, meaning your LAN dies (literally no communication / internet can get through).

Router IGMP Setting

I guess the sonar/radar devices were not truly designed to work across standard point to point IP, as this method of broadcast TCP/IP communication is not very efficient. Most likely it is caused by a network architecture constraint/decision, since the radar doesn’t have to know the IP address of the MFD for point to point comms, instead it just broadcasts its data as multicast packets for any and every device to hear.

Most routers can be configured to stop IGMP packets from flooding the wifi (like the Wifi1 does) so it shouldn’t present a problem. The only downside with disabling IGMP packets is that some other network discovery services (such as Bonjour, automatic discovery of LAN devices etc) won’t work whilst disabled.

This is the payoff. Enable IGMP routing and everything on your network works fine, but when you turn on the radar your LAN and Wifi grinds to a halt, or block IGMP routing and the LAN all works fine, the radar shows on your iPad, internet works etc, but Apple and other multicast device discovery systems don’t work.

Just to be clear, this only occurs when connecting the NSS into your own LAN network so you can access it via your normal boat wifi. Simrad recommend you use their proprietary Wifi1 router as a private network with private Wifi. This is fine, but means users have to change wifi networks to use the NSS/iPad/NMEA connectivity. (which I didn’t want to do)

For me its not really a show stopper. I just leave my router normally in the disable IGMP mode, and when my wife complains she can’t wirelessly transfer images from her iphone to computer with the PhotoSync app (which advertises it’s presence via multicast) I enable it temporarily. Its not 100% ideal, but a small price to pay for the excellent ipad to NSS connectivity.

I’m currently experimenting with VLANS and segmenting my network just in case I can configure a way around the problem.

Slicing the NSS to Radar cable was no problem. It is standard cat5, and you can crimp plugs on and simply connect it into and out of a lan switch or wifi router.

If you’ve done CAT5 cables before, then its easy. You can splice the cable and use it via your own wifi router at the moment and use a pass through connector to re-join both ends later if you finally get a wifi1.

This was my approach and it works fine.

{ 8 comments… read them below or add one }

Xavier Itzmann April 18, 2015 at 23:58

We have a WIFI-1 onboard but it is a disgrace to have to switch wifi networks to use the Simrad devices or to use internet services.

What I’d like to know is how to connect the WIFI-1 to the Cisco so it all works automagically.



Adrian April 19, 2015 at 04:00

The wifi1 only has two network ports, and is designed to go in between the chart plotter and the radar, so it has no capability for connecting to another internet router as well.

I think the best and safest mode of operation is to have a Nav wifi network and a boat wifi network and keep them separate. It’s a bit of a pain but if you have the wifi1 is the best way to go. Alternatively you don’t have to use the wifi1 at all and just connect the chart plotter and the radar network leads to your main router. There is a big however, as the radar tends to flood the network, and causes other network connectivity to fail.


Adrian April 19, 2015 at 04:36


I noticed your comment on panbo. It seems the wifi1 is quite limited and was never really intended as a bridging device. I fear the b&g Zeus touch v1 kit I have is now too old to take advantage of the latest connectivity enhancements. I’d guess navico will bring out a wifi2 later this year. Meanwhile, have you tried connecting everything through your Cisco router and not using the wifi1 as per my old post.



Xavier Itzmann August 19, 2015 at 00:36

Thank you Adrian.

You are correct that WIFI-1 has two ports, but you are not correct that WiFI-1 needs sit between plotter and radar: on our two year-old installation, only one of the two ports has been in use, and yet there has been frequent use of the GoFree iPad and iPhone apps.

But I do thank you for having followed up! And if I find anything out, I’ll be sure and let you know.



cowelld April 12, 2013 at 17:56

I’ve tested the NSS and BR24 using a hub and found the ICMP and IGMP packets made up only .04% of the 802 data stream. Perhaps the router is causing the NSS to generate excessive IGMP’s. My WIFI routers are too old to have the diabling feature for IGMP so I can’t test that. The D-link unit shows the packets being dropped as “Ping of Death” types. The Linksys unit doesn’t say why it dropped them. Perhaps your router is mis-categorizing the UDP packets. I’ve seen Wireshark brand them as mal-formed.
I’m using the OpenCPN BR24 plugin as a front end for the data stream and strangely it shows a brief radar display and then stops. The same program will also receive and display the GOFREE Tier1 NMEA/TCP/IP datastream with no problem.
What kind of Router are you using. Is it 12v?


Adrian Evans April 15, 2013 at 11:17

It is a Vigor 2920n. It is 12v with a proper on/off switch (not push to toggle type) so can be fixed out of the way. It allows multiple WAN sources and supports USB phone dongles, so if my wifi antenna (a Rogue Wave long range device) isn’t present it’ll automatically establish and share an internet connection via the cellular modem id plugged into the USB port.

It also is SIP and VOIP capable, has VPN capability and can share usb HDs.


Dan Hacking February 15, 2013 at 06:58

Google normally provides a good translation service, it turns out it doesn’t understand the language of “uber geek” ;-)


Parsley72 February 15, 2013 at 05:14

That’s not quite correct. Bonjour and other service discovery protocols should work fine if they’re using multicast because IGMP Snooping only blocks multicast data when no device on the Wifi side wants to receive it. If you have an iPad connected to Wifi it will join the Bonjour multicast. IGMP Snooping should spot this and allow the multicast for Bonjour to be transmitted on the Wifi, so your service discovery should work as normal. If you’re finding it doesn’t work then it maybe IGMP Snooping isn’t implemented properly on your router.


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