Wireshark-users: Re: [Wireshark-users] Using Wireshark for a DSL "link no surf" problem
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From: Martin Visser <martinvisser99@xxxxxxxxx>
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).




On 19 June 2014 16:14, Kok-Yong Tan <ktan@xxxxxxxxxxxxxxxxxxx> 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.

-- 
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P.O. Box 565, Gracie Station        #   Apple Certified Consultant
New York, NY 10028-0019            #   Apple Consultants Network member
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On Jun 18, 2014, at 21:02 , Frank Bulk <frnkblk@xxxxxxxxx> 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@xxxxxxxxxxxxx [mailto:wireshark-users-bounces@xxxxxxxxxxxxx] 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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx



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On Jun 18, 2014, at 1:34 PM, "Kok-Yong Tan" <ktan@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxx> 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@xxxxxxxxx> wrote:
Some Comtrend modems can do a port mirror of the WAN (DSL) side.

Frank


-----Original Message-----
From: wireshark-users-bounces@xxxxxxxxxxxxx
[mailto:wireshark-users-bounces@xxxxxxxxxxxxx] 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@xxxxxxxxx> 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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