Browsers Failing to Display Certain Web Pages

Posted: July 18, 2012 in SBS 2011
Tags: , , ,

Imagine my surprise to do a new install of SBS at a client and find that I was unable to get certain web pages to resolve using either IE or Firefox.  A great many other web pages worked just fine, but not http://www.yahoo.com nor http://www.microsoft.com.  I imagine there were others, but at least those two.

By not display properly, i mean that the status line on the browser displayed “waiting for response…” without ever doing anything.  Maybe for 10 minutes or more, but sometimes less with a cannot display the web page message.

Hers’s what did work:

  • Pinging the url got a response or at least resolved the IP address correctly
  • Tracert could follow out to the site or close enough

Those tests indicated that network connectivity was fine and that DNS was working.  But still no….

Not only did this affect the SBS server, running as a hyper-v virtual machine but also the host server.  And client computers on the LAN. Maybe a DHCP problem?  Nope, changing to static IPs on the clients didn’t solve the problem.

Then someone happened to mention that the ISP was Qwest/Century Link and were there some problems with the connectivity limits?  Obviously no filtering or blocking, Why? Because we could plug a laptop directly onto the modem and resolve the web sites just fine.

But it created a question.  What about MTU size?

Turns out that was it.  By reducing the MTU from 1500 to 1480 on the interfaces, problem solved.

Here’s what to do:

  1. Open command prompt (you may need it as administrator).
  2. Enter netsh interface ipv4 show subinterfaces
  3. This will give you a display like
    MTU  MediaSenseState   Bytes In  Bytes Out  Interface
    ——  —————  ———  ———  ————-
    4294967295                1          0   14305131  Loopback Pseudo-Interface 1
      1500                1  10662560242  2587625280  Local Area Connection
  4. You will use this information in the next step
  5. Enter C:\Windows\system32>netsh interface ipv4 set subinterface “Local Area Connection”  mtu=1500 store=persistent
  6. If your connection is named something else, substitute it.
  7. The system responds with “Ok.”
  8. Run the show command again to verify settings.

Not only did this fix the problem, it significantly speeded up the load time for web pages in general.

I hope this saves you the several days of searching and scratching your head that I went through.

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Comments
  1. chatroulete says:

    I simply could not leave your web site before suggesting that I really enjoyed the standard info a person provide
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    Like

  2. You are most generous in your comments and (I assume!! LOL) praise.

    Here is my guiding principle: I get so frustrated when searching for possible technical solutions that appear in forums and blogs, for the most part, that the writers seeking or providing help just fail to be specific and complete so that anyone, not just the participants, could follow along and replicate the solutions. So I vow to present both problems and solutions in as complete light as I can, and folks like you make me understand that I am not wasting my time.

    Please do come back often. You will always be welcomed.

    Like

  3. Jeffrey, Upstate NY says:

    There is a typo in the set command in step 5:

    “mtu=1500” should be “mtu=1485”

    Also, if copying and pasting this command to the command prompt, delete and retype the quotation marks. For some reason copying quotation marks from web pages does not seem to work, even though it appears identical in the command window (it is converted into a different ASCII character, which is not compatible with the command syntax).

    Like

  4. Thanks for the catch.

    Like

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