[Mikrotik] mssql client dragging over 4.16 l2tp

corey freeman corey at freephoenix.net
Wed Mar 23 16:21:20 CDT 2011

Main office is fiber via a local telco as well as the working remote.
The remaining two offices are on Cox cable.

Remotes are routing to main office network for rdp/email/client
apps/printing, etc.
"Normal" internet traffic works great everywhere.

I initially had an issue with traversing cox's network with pptp
connections.  They would build up fine and ping ok, but whenever you
ran any traffic it would slow down to 1-2k.  Switched them to l2tp and
now I'm running 12mb down/5mb up from each of the remaining two
locations.   I did just notice that the bandwidth test had problems
running a 'send'  tcp test.  Wouldn't connect for the first dozen
times I tried it.

In the process of troubleshooting the pptp links over Cox, the mtu and
mru was dropped to 1450.  Any higher and I started dropping pings and
bandwidth suffered greatly.

I think I've narrowed down the issue to two possibilities.  1. I have
an isp that's over agressively qos my traffic. (either the fiber
telco, or Cox)  2. I have a configuration issue on my equipment.
I'm going to have a hard time nailing down #1 if that's the issue.
#2.  I'm ready to have a second set of eyes on the config and setup
and let me know what's up.


On Wed, Mar 23, 2011 at 2:57 PM, Butch Evans <butche at butchevans.com> wrote:
> On 03/22/2011 10:20 PM, Corey Freeman wrote:
>> Hello guys,
>> BUTCH: I'm trying not to go into too much detail in case I'm breaking some
>> list rules..
> No worries.  This is an appropriate discussion.
>> If someone can help off-list, please let me know.  I'm not necessarily
>> looking for free help.
> I can assist if needed, but may be able to help here, too.
>> I have 3 remote offices connecting back to a main office.  All are rb750
>> or
>> 450g, 4.16.  All connections are 20mb/5mb or faster (60/15 at main
>> office).
>> I'm trying to troubleshoot a client application that is heavy SQL based,
>> and
>> I'm somewhat stuck.  One of the remote offices is on the same isp as the
>> main office, and clients there are having no issues.
>> When the app loads, it's repeatedly requesting (and receiving) information
>> from the server, but is not acknowledging it.
>> I'm expecting to find some sort of MTU issue or other PPP setting
>> affecting
>> the traffic.  So that's why I'm posting this here.
>> I can supply configs as well as a wireshark capture of the client.
> I am guessing that you have a main office that is connected with dsl?  To
> that main office, you have 3 remote offices connected via l2tp, 1 of which
> uses the same ISP as the main office (you stated that last part) and is
> connected via dsl as well.  How are the remote offices connected to the
> internet?  Does "normal" internet traffic run well on all locations?  Is the
> l2tp being used to bridge the offices together, or is it routed?
> --
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