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UDP Traffic flooding with Airport Express behind switch


UDP Traffic flooding with Airport Express behind switch

Hi there - I'm hoping someone can help me solve an issue with my AT&T Uverse internet setup.  


First a little background; Our AT&T service comes into our guest house/office to the AT&T router/gateway, and is then fed via a hard line from the RG into our house to an AT&T supplied Netgear GS108 switch which then feeds a number of STBs.  We then have an Apple Airport Express connected to this switch which feeds the house computers wirelessly.


When I first set this up, I set up the AEX incorrectly in a double NAT configuration - I would much prefer to have it in bridge mode to allow smoother access between all parts of my network, but when I put the AEX into bridge mode (the 'correct' setting), the computers on the AEX wireless become completely flooded by UDP traffic if any of the STBs are on and especially if they're recording.


Apparently the RG can't implement IGMP through the Netgear switch?  How can I get the AEX into bridge mode but get the RG to implement IGMP through the Netgear switch?


Any thoughts on this?


Many thanks in advance.



Message 1 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Thanks for the reply.


No, I did not configure any VLANs on the GS116e.  The only switch I wanted to eliminate the multicast issue on was the GS108e and did not really mind if there was an issue with devices on the GS116e.  I thought I could utilize a VLAN on the last segment of my network to eliminate the multicasting there but, now that I think about it some more I guess I understand.


I need to configure a VLAN and tag ports on the GS116e so that traffic can properly get back the the RG from the GS108e? 


It's a shame because I was considering the T switch, but opted for the E because of the v3 support.  It turns out that does not work with U-Verse.  I would love HTTP access to the switch because I have to RDP to a Windows machine to manage the E switches.


I'll give it a go, but I did see that thread over at DSL Reports earlier today, so I will cross my fingers.  I appreciate the help.

Message 16 of 35

Re: UDP Traffic flooding with Airport Express behind switch

I have a similar setup and issue. After much trial and error, I came upon this post and wanted to be sure my concept of how I can "fix" the issue is correct.


I too have the Uverse router and an AirPort, except I have an unmanaged gigabit switch directly attached to the Uverse router, then my network devices feed off of that.  With previous ISPs, this wasn't an issue.  With Uverse's use of IGMPv3, it's problematic.  I have three STBs; one is connected to the Uverse router, the other two through the unmanaged gigabit switch, as they also have data on those network runs.  If I add a wireless access point, like an Airport or any other brand, even if the line it's on doesn't have a STB, the device becomes inoperable within a short period of time.  Again, this is plugged in through the gigabit switch behind the Uverse router.  Wired network interfaces all work as anticipated.  Wireshark shows a broadcast traffic packet storm on the wireless access points.  I want the access points on a gigabit network;  the Uverse's 10/100 ports would degrade overall network performance compared to 802.11n or gigabit capable wired clients.


The question is, if I replace the central unmanaged gigabit switch with one that can handle IGMPv3 traffic properly, should that suffice in allowing me to add wireless access points elsewhere without seeing the multicast packet storm?  I would think then it shouldn't start hitting the access point in my office, which is the only device plugged into that network drop if that centralized switch handles the data properly.  I have other desktop gigabit switches around at endpoints, but they all would go through the IGMPv3 capable central switch. 



Message 17 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Simply replacing the central switch with one that is IGMPv3-snooping capable will not solve the problem. Since there is a mixture of STB units and computers on the downstream switches, IPTV multicast traffic will still flow to the downstream switches whenever an STB is powered on.

Furthermore, I know of no consumer-affordable switches that implement U-Verse-compatible IGMPv3-snooping.

Your best bet is to use VLANs as described above.
Message 18 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Thanks for the response.  I have access to beefier switches, some of which do have IGMPv3 snooping capabilities.  


Just to be sure, even if I have a IGMPv3 capable switch, if I have a STB and a WIFI access point on attached to it, I'll still see the same symptoms?  For example, this somewhat how my network looks now:


AT&T router  < - Port 1 - > STB 1

< - Port 2 -> Central Gig Swtich <- Port 1 -> AirPort (WIFI & LAN) <- LAN Ports -> Computer 1, Computer 2, etc

              < - Port 2 -> Gigabit Switch < -> STB, PS3, Computer2

  < - Port 3 -> Gigabit Switch < - > STB, PS3, Xbox, Receiver, Apple TV


So, If I replace Central Gig Switch, which is unmanaged and consumer grade, with one that's IGMPv3 capable, the AirPort on port 1 will still get slammed with multicast traffic from the TVs on ports 2 and 3 of that switch?  The remote switches probably are getting hit with the broadcast storm too, except they're not showing degraded performance.  It's only when I add in WIFI access points into the scheme where I see any issue and that's when it's on a shared line (ie - on a switch with a STB at the end point) or if they're on their own dedicated line, but still have a common backplane of the consumer switch.  I figured since the Uverse box handles the IGMPv3 and should (in theory) allow me to hook any host/client (WIFI access point, computer, etc) to it without seeing a broadcast storm, putting a switch that supports IGMPv3 should allow me the same, but I could be missing a key point here.  


Thanks again for your response. 

Message 19 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Ouch. Seems that I can't format my diagram right.  I tried a few different ways and it always is skewed.  In a more simplistic way, if I have:


2Wire Router



      + Port 1 ---------- STB #1

       |                      IGMPv3 Snooping Capable Gigabit Switch 

      + Port 2----------- + Port 1


                                    + Port 2 ---------------- WIFI Device

                                     |                            Unmanaged GigE Switch

                                    + Port 3 ----------------- + Port 1


                                                                           + Port 2 ---------------- STB #2


                                                                           + Port 2 ---------------- Computer 1



In this scenario, the WIFI device in Port 2 of the IGMPv3 capable switch will be adversely impacted by the STB #2 plugged into Port 2 of the Unmanaged GigE Switch, which links back to Port 3 of the IGMPv3 capable switch?  Or if a STB was just simply plugged into the IGMPv3 switch?

Message 20 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Another solution is to only connect the STB(s) to the RG and connect one of the other ports on the RG to a switch or router to be used with non STB devices.  This way no IPTV traffic will be sent to the port serving the computer network.


I had an issue with IPTV traffic flooding my network because my RG was connected to a switch downstairs and the switch was then connected to a STB, a PS3 and a computer.  I resolved this issue by using the HPNA (coax) connection downstairs for the STB instead of an ethernet connection.  My only STB using an ethernet connection is upstairs next to the RG.

Message 21 of 35

Re: UDP Traffic flooding with Airport Express behind switch

OK, if your only goal is to keep multicast IPTV traffic away from the AirPort, then yes, an IGMPv3-snooping switch in place of your current unmanaged central switch would indeed do that.

But you will still get mixed computer and IPTV multicast traffic on the downstream switches. You say this has not resulted in degraded performance, and if that's true then it's no big deal.

If you do this and you get it to work, please post back what brand and model switch you're using in place of the central switch and any configuration settings, if applicable. To my knowledge, no one has successfully implemented ANY 3rd-party IGMPv3-snooping switch into a U-Verse system and had it work properly.
Message 22 of 35

Re: UDP Traffic flooding with Airport Express behind switch


Eric -
Yeah, agreed.  Unfortunately, I don't have that option with the layout right now.  I have single drops in the areas and some of those areas have multiple devices.  I had thought about just taking them wireless, but there are still a few devices that would need a wired network connection. 
Message 23 of 35

Re: UDP Traffic flooding with Airport Express behind switch

SomeJoe - 


It mostly is just to keep stability.  Outside of the issue with the wireless access points, I haven't had any of the other networking gear cease up.  I've considered the VLAN approach too.  Preferably, I'd like this to be something that anyone could upkeep, not just someone who has an understanding of network topologies and setup! Smiley Wink


I'll give both a bit more thought.  I appreciate the insight!  I'll post in what I eventually try. 

Message 24 of 35

Re: UDP Traffic flooding with Airport Express behind switch

I'm also reconsidering just running the two STBs directly to the Uverse router, despite each being on their own gigabit switches at the end points.  In reality, the more I think about it, the only device on those switches that truly benefits from gigabit speeds is the Mac mini.  The game consoles aren't used for streaming content within the network.  I could just run that Mac over 802.11n.  With two access points, I should have a very strong signal throughout.  It won't be gigabit speeds, but it'll be faster than being wired to the Uverse router and should still be plenty fast enough for most everything it's used for.


On that note, playing around with networking always has its charms! Smiley Wink

Message 25 of 35

Re: UDP Traffic flooding with Airport Express behind switch

I got to ask because there is a big difference in range you said Airport Express (about the size of a pack of cigs) which has a limited range (i use one in my media room) and Airport Extreme (about 8 x 8 x 1.25 ) which has a very good range or at least the new dual bands do it reaches both front and backyard at my home.

Message 26 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Sure.  I have an Airport Extreme.  I must have mistyped.  I also have some Cisco wireless gear.  I would think I should be able to blanket multiple levels between them pretty well.  


I have the dual band, as well.  I've been happy with it!   Smiley Happy

Message 27 of 35

Re: UDP Traffic flooding with Airport Express behind switch

I hate to necro an old thread, but holy crap, thank you for this!


I was able to mimic this setup using 2 DIR-825 routers running openwrt, on which I spent less than $100.  Even managed to incorporate having the RG-connected router run in DMZ+ mode off of the RG by connecting the WAN port on the router to the RG instead of one of the switch port.


As it turns out, setting that PVID parameter for each port turned out to be the key I was missing.  I even managed to bundle in WiFi and a separate guest WiFi network, all over a single trunk line with the TV signal, all appropriately isolated from each other.


So yes, this is possible, even with cheap routers, when you can use 3rd party firmware like OpenWrt.


Thank you again!

Message 28 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Great, glad this helped out!
Message 29 of 35

Re: UDP Traffic flooding with Airport Express behind switch

Joe, sorry for replying to an old post, but I'm diving into the world of VLANs myself. I actually have two separate networks in my house, one for U-verse TV, and one for Time Warner Cable Internet. I am going to combine these over physical cables using VLANs, and also use VLANs to isolate my home lab servers from my casual home Internet access users.


I wanted to point you all to a blog post I made, which tries to explain how VLANs really work, and get your take on it. It's a work in progress so comments are welcome. As I build out my network I will add actual examples.


Here's the blog post:



Message 30 of 35
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