[NTLUG:Discuss] Network 'passthru' viewer

[David Simmons]

Just a 'report back'....since my issues were intermittent with FIOS, I'll
have to use/try it for a few days - but I will say, saying the MTU to 1400
has really made the network / internet noticeably peppier!

Thanks - great insight and suggestion,

-dave

On Wed, Jan 26, 2011 at 1:20 PM, David Simmons <dave at dgnal.net> wrote:

> Preston - wow...that's some great intel to try...thanks!   - dave
>
>
> On Wed, Jan 26, 2011 at 11:49 AM, Preston Hagar <prestonh at gmail.com>wrote:
>
>> On Mon, Jan 17, 2011 at 9:44 PM, David Simmons <dave at dgnal.net> wrote:
>> > Guys/Gals,
>> >
>> > Help me to understand what software/hardware is necessary to compete the
>> > following task.
>> >
>> > I have Verizon FIOS...recently the quality of service has been bad
>> (meaning
>> > I try to go to a website and it times out)..but at times of the it works
>> > great.  Even when I believe it's not working well (as indicated by
>> trying to
>> > log into the local Verizon router and it taking ALONG time to respond) I
>> see
>> > the lights flickering.  SO, I think to myself, "Who's fault is this?"
>>  Do I
>> > have a hacked machine that's spitting out spam/junk?  Is it my side or
>> their
>> > side?
>> >
>> > So I figure if I had a system/laptop/whatever with two network cards - I
>> > could setup network pass-through or bridging so that I could
>> > see/categorize all of the packets that are flowing through (seeing their
>> > source & destination IP address.....and having some sense of the content
>> of
>> > the packet - beit email, web, etc, etc).
>> >
>> > I was originally thinking an IPCop setup...but realized that I don't
>> want
>> > ANY firewalling going on...just want the data to flow through and
>> > watch/sniff/see what it is?
>> >
>> > Any help / ideas / webpages would be appreciated,
>> >
>> > -dave
>> >
>>
>> At the company I work for, we have Verizon "Business" Fios on a 35
>> down / 35 up plan.  A few months back, seemingly random (we figured
>> out later they weren't random) webpages seemed to load, time out or
>> have other weird issues.  We were, at the time, using a custom built
>> FreeBSD router that had a Cat 5 run from the ONT to the router.  We
>> figured maybe something was wrong with the router, or DNS or our LAN
>> and spent forever trying to find the answer.  Finally, we came across
>> it, MTU.
>>
>> Apparently on the peers that our Verizon FIOS hops through, there is a
>> MTU black hole.  The peer with the black hole was part of the route
>> for a lot of major sites, but the most reliable (to break that is)
>> that I found were provantage.com, newegg.com, and microsoft.com.  We
>> found empirically (we ran traceroutes and pings, gradually increasing
>> the packet size until it it would be dropped) that by setting the MTU
>> of our router and machines to 1400 (instead of the default 1500) the
>> issues went away.  To confirm it wasn't faulty hardware anywhere under
>> our control, we tried using our Logix T1 connection and would have no
>> issues accessing any site (including the 3 mentioned) with the same
>> router and same hardware.  We also tried using Verizon's Actiontec
>> router and it experienced the same issues as our FreeBSD router.  We
>> tried talking to tech support and generally just got "we'll look into
>> it, or everything looks fine on our end".  In the end, we just set the
>> MTU to 1400 for everything and gave up trying to get Verizon to fix
>> it.  We haven't noticed any major decrease in performance using a
>> smaller max packet size and now all sites load quickly and normally.
>>
>> Anyway, if you experience issues with time outs again, you might try
>> lowering the MTU of your machine and router to 1400 (or somewhere
>> along those lines) and see if that helps.
>>
>> For Linux machines, the command to change the MTU is
>>
>> ifconfig <network device> mtu 1400
>>
>> where <network device> is eth0 or whatever your network card is named.
>>  Where to configure it permanatly depends on your distro.
>>
>> If it doesn't help or make any difference, you can always set it back
>> to 1500 and no harm done.
>>
>> Preston
>>
>> _______________________________________________
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>>
>
>
>
> --
> Those with sight believe what's believable. Those with vision know what's
> unbelievable.
>



-- 
Those with sight believe what's believable. Those with vision know what's
unbelievable.