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I have three internet providers at my office: Telepacific (3/3Mbps), SkyRiver (12/12Mbps), and Verizon FiOS (75/35Mbps). (The reasons for three connections are outside the scope of this issue.) I have a small LAN that sits behind a SonicWall TZ-215 and I use the spillover method to take advantage of the available bandwidth of FiOS (primary) and SkyRiver (secondary) with Telepacific being the failover for the both of them.

About two weeks ago I noticed I wasn't able to reach theverge.com. I didn't bother doing much troubleshooting because it's just a tech news site so I gave it a few days. The problem remained so after a little troubleshooting of DNS (which resolved and still resolves) I changed the priority of the two connections and it loaded right up.

Fast forward a few days and now this week I come to discover that veeam.com also does not work on FiOS. DNS resolves fine.

Neither site responds to pings and accessing them by IP address also gets me nowhere.

During some experiments on changing priorities and trying different websites I found that nginx.com will not load on SkyRiver. And since last Thursday we've been having intermittent problems with Microsoft Dynamics CRM pages loading. Keep in mind that the websites that fail to load (on their respective ISPs) fail 100% of the time whereas CRM loads most of the time. CRM being what it is (a hosted service from Microsoft) there's almost no way for me to find out if it's on their end or mine. Their tech support in India, while very friendly and eager to help, seem to have no ability to troubleshoot this kind of issue.

I have put in a request to Verizon but, because a tracert shows the connection getting outside Verizon's sphere of influence, they have been mostly unhelpful. However, it is very strange that two websites are basically non-existent while on their network and two other ISPs do not share the same problem.

My next step for troubleshooting will be to take the SonicWall completely out of the picture and hook up a laptop to each ISP independently and see what happens. I can't imagine that this will change anything but the router's configuration did not change let alone change in such a way that these two specific sites would be blocked.

edit:

Results of MTR run to theverge.com

|------------------------------------------------------------------------------------------|
|                                      WinMTR statistics                                   |
|                       Host              -   %  | Sent | Recv | Best | Avrg | Wrst | Last |
|------------------------------------------------|------|------|------|------|------|------|
|   l300.lsanca-vfttp-133.verizon-gni.net -    1 |  503 |  502 |    1 |    3 |   66 |    2 |
| g0-10-2-0.lsanca-lcr-22.verizon-gni.net -    1 |  492 |  488 |    0 |    5 |   19 |    4 |
|so-5-1-0-0.lax01-bb-rtr2.verizon-gni.net -    1 |  495 |  492 |    0 |    7 |   95 |    8 |
|         0.xe-11-1-0.br1.lax15.alter.net -    9 |  376 |  343 |    0 |   19 |   93 |   30 |
|te0-0-0-2.ccr21.lax05.atlas.cogentco.com -   69 |  136 |   43 |    0 |   47 |   55 |   51 |
|   be2025.mpd21.lax01.atlas.cogentco.com -   87 |  113 |   15 |    0 |   53 |   74 |   68 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                          38.104.116.126 -    7 |  408 |  383 |    0 |   16 |   27 |   20 |
|      border2.po1-bbnet1.phx008.pnap.net -   16 |  313 |  264 |    0 |   15 |   54 |   15 |
|                            70.42.228.75 -    7 |  408 |  383 |   14 |   15 |   26 |   15 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|                   No response from host -  100 |  101 |    0 |    0 |    0 |    0 |    0 |
|________________________________________________|______|______|______|______|______|______|
   WinMTR v0.92 GPL V2 by Appnor MSP - Fully Managed Hosting & Cloud Provider
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Are you using asymetrical NAT? The responses will likely come back by a different route, from a different source IP. –  Dru Aug 23 '13 at 4:36
    
@Dru I didn't know what that was until this morning but I believe so, yes. We use traditional NAT to provide a private LAN and I also have several servers that I've assigned public facing IPs. It gets a little more complicated than that too because I have multiple public IPs for the same device. I just did a test from my Exchange server and I think you are on to something. Each site is working but do not work from my workstation. –  idon'twearsuits Aug 23 '13 at 15:31
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1 Answer

Get mtr (from repo if *nix OS, or from here if Windows), and use it on the failing site when it's failing, let it run for a good 5 minutes, post the results.

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