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Re: Using Wireshark for a DSL "link no surf" problem

From: Martin Visser <martinvisser99 () gmail com>
Date: Thu, 19 Jun 2014 17:36:32 +1000
There seems to be a lot of contradicting answers on this thread. PPPoE is
used for authentication AND  link negotiation (ie providing IP addresses)
AND encapsulation. If you have a PPPoE modem in passthrough (which is what
it sounds you are doing), the modem is just pretty much doing physical
level translation between your DSL and Ethernet, and then your router
(normally) is establish the PPPoE session. If you aren't able to capture
traffic at the router and/or want to test locally you can use a PPPoE
client on a laptop, for instance, and which also can run wireshark. Not
sure what you have a available, but if you plug your Windows laptop into
your modem directly, and then run through the Internet connection wizard
(as per the example here - http://www.tp-link.com.au/article/?faqid=339 )
while running Wireshark you may have a better clue as to what is going on
(or not).


Regards, Martin

MartinVisser99 () gmail com


On 19 June 2014 16:14, Kok-Yong Tan <ktan () realityartisans com> wrote:


The service provider doesn't use DHCP to hand out my static IPs.  I was
assigned them via an email.  The DHCP server is on the DSL modem (not the
DSLAM) and it hands out a single IP address in the 192.168.1.0/24 private
range, namely 192.168.1.10.  This is known as out-of-band management and
only used for accessing the DSL modem itself and nothing else.  The actual
static addresses I'm assigned are in the public range while my DSL modem is
supposedly set to bridging mode, i.e., it's not in the 10.0.0.0/8,
172.16.0.0/12 or 192.168.0.0/16 ranges.

--
Reality Artisans, Inc.              #   Network Wrangling and Delousing
P.O. Box 565, Gracie Station        #   Apple Certified Consultant
New York, NY 10028-0019            #   Apple Consultants Network member
<http://www.realityartisans.com> #   Apple Developer Connection member
Cell: (646) 327-2918 #   Ofc: (212) 369-4876

On Jun 18, 2014, at 21:02 , Frank Bulk <frnkblk () iname com> wrote:

If your service provider uses DHCP to hand out those “static” IPs, or
their access gear allows that IP address to be entered (which is the case
with our vendor’s gear), the access gear prevents someone else taking your
static IP.

Frank

*From:* wireshark-users-bounces () wireshark org [mailto:wireshark-
users-bounces () wireshark org] *On Behalf Of *Kok-Yong Tan
*Sent:* Wednesday, June 18, 2014 1:58 PM
*To:* Community support list for Wireshark
*Subject:* Re: [Wireshark-users] Using Wireshark for a DSL "link no surf"
problem

Yes, I understand why they gave me a /24 but with a /24, all it takes is
for somebody else on the same subnet to accidentally (not intentionally or
maliciously for obvious reasons) take my static IP and thus blow me out of
the water without affecting them too much.  I had this happen once.  With a
subnet between /24 and /30, they'd notice when their accidentally typo-ed
IP address didn't work because it didn't match their gateway info.
--
Reality Artisans, Inc.                          #   Network Wrangling and
Delousing
P.O. Box 565, Gracie Station              #   Apple Certified Consultant
New York, NY 10028-0019                 #   Apple Consultants Network
member
<http://www.realityartisans.com>       #   Apple Developer Connection
member
Cell: (646) 327-2918                           #   Ofc: (212) 369-4876

On Jun 18, 2014, at 10:59 , "Jamie O. Montgomery" <
Jamie.Montgomery () comporium com> wrote:


PPPoE is used for authentication. If you have a static IP, they know who
has it and you don't need authentication. PPPoE would be the termination
point for the address, but since it will reside on your firewall, the modem
needs to bridge the dsl network to the Ethernet network on the public side
if the firewall


They give you a /24 because they'd be burning up more IPv4 addresses
giving you a smaller subnet. Other static IP customers use addresses in
that subnet along with you.

*Jamie Montgomery | Comporium*

Network Facilities Engineering | Engineering Associate II

www.comporium.com

jamie.montgomery () comporium com



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On Jun 18, 2014, at 1:34 PM, "Kok-Yong Tan" <ktan () realityartisans com>
wrote:

No, the DSL modem is bridging, not routing.  I've been assigned two static
IPs (although they've given me a /24 net mask!!!) and my firewall is
assigned one of them.  The firewall is connected directly to the DSL modem
by Cat6 patch cable.  The other IP is unused (I use it for testing VPN
configurations).

I'm not sure but since the Broadxent Briteport is a PPPoE modem, I assume
PPPoE.  But the tech says that's not correct (WTF?).  And he can't explain
what they use.  Sigh.
--
Reality Artisans, Inc.
#   Network Wrangling and Delousing
P.O. Box 565, Gracie Station
#   Apple Certified Consultant
New York, NY 10028-0019
#   Apple Consultants Network member
<http://www.realityartisans.com>
#   Apple Developer Connection member
Cell: (646) 327-2918
#   Ofc: (212) 369-4876

On Jun 17, 2014, at 22:13 , Pedro Tumusok <pedro.tumusok () gmail com> wrote:


Well if the tech can see stuff, its not what I thought might be the
problem, which was PVC settings.

But does your modem get an IP address, ie is it setup as a router or does
your computer get the ip address?
Are you using PPPoA/PPPoE etc?


On Wed, Jun 18, 2014 at 5:52 AM, Frank Bulk <frnkblk () iname com> wrote:

Some Comtrend modems can do a port mirror of the WAN (DSL) side.

Frank


-----Original Message-----
From: wireshark-users-bounces () wireshark org
[mailto:wireshark-users-bounces () wireshark org] On Behalf Of Kok-Yong Tan
Sent: Tuesday, June 17, 2014 4:53 PM
To: Community support list for Wireshark
Subject: Re: [Wireshark-users] Using Wireshark for a DSL "link no surf"
problem



On Jun 17, 2014, at 14:28, Jaap Keuter <jaap.keuter () xs4all nl> wrote:


On 06/17/2014 08:42 PM, Kok-Yong Tan wrote:
Is it possible to use Wireshark to troubleshoot a DSL "link no surf"

problem?  The ISP insists it's a CPE issue but the problem only started
after their Tier 1 tech monkeyed with the DSLAM and/or the CPE (remotely)
in
some manner.  I find it suspicious that the problem was intermittent packet
loss until they tinkered, whereupon the problem became a "link no surf"
issue (i.e., there's Layer 2 connectivity but zero Layer 3 traffic
passing).


Depends on what you can trace in the CPE, as in, how close to the DSL

interface.

Otherwise you'll need capture hardware on the DSL....

Good luck,
Jaap



I can get up to the DSL modem itself.  In hindsight, I'm thinking this
isn't
going to be of much use and the only way to debug this is with capture
hardware on the DSL side as you suggested.  Drat.
--
Sent from my iPad2 with greater chance of typographical, grammatical and
other disasters.  Your indulgence is even more humbly requested.
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--
Best regards / Mvh
Jan Pedro Tumusok
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