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Speakeasy Speed Test


Advanced ADSL Troubleshooting

This document helps to explain a little bit about the Telstra Wholesale DSL network, and how the service is provided to another ISP, such as Pacific Internet, IPrimus, Netspace, Internode & IInet. 
It also aims to help users quickly identify faults on the DSL network, and how the network integrates into their own. 
To start with, I have divided this document up into the 4 ways that your phone line can be provisioned for DSL by Telstra.

A Type A Connection is a conventional PPP-based connection over Ethernet or ATM

About Telstra

The Telstra-based PPP over Ethernet/ATM looks like this.

Type A Diagram

A similar config is used for Pacific Internet / Netspace / IPrimus DSL connections that go through the Telstra Wholesale Network. 
The most common point of failure within this setup is the link between the IPSN and the CMUX. 
The CMUX is located at your local exchange, whilst the IPSN is also reffered to as an "Access Concentrator". 
There are currently 6 Access Concentrators use by Pacific Internet on the Telstra network


Each server has an internal IP address, starting with 172.31, that linux users will occasionally see, although this means nothing in the real world as far as gateways and routing goes. 
The authentication process relies on many points functioning within the Telstra Network. 
This is where the highest point of failure is. When you authenticate using PPPoE/A, these are the devices that 'talk' to each other.

        Your PC/Network 


Phone Line 


Access Concentrator/IPSN/Shasta

Telstra Radius Proxy

ISP Radius Server 

Rest of the Internet 

Telstra have provided a definition of some of the terms used to describe their network. 
Telstra authenticates users using a device called a "Shasta". This is made by a company called Nortel, who have a website about their product The current software being used is.

V3199:T4:L35:Shasta 5000: iSOS (tm),\000

Some people make the mistake of thinking that just because an ISP resells the Telstra DSL service, they are also using Telstra's overseas and domestic links. This not the case. In Pacific Internets situation, all data flows from the telstra network in each state through to a Pacific Internet router. For example:

 1  ADSL.mel.pacific.net.au (.201)  32.845 ms  37.389 ms  45.695 ms
 2  a6-0-1.mel001.pacific.net.au (.85)  27.158 ms  26.011 ms  27.609 ms
 3  FastEthernet0-0.mel003.pacific.net.au (.162)  32.145 ms  26.874 ms  32.456 ms
 4  comindico.gw.pacific.net.au (.165)  32.596 ms  27.187 ms  32.416 ms
 5  pos2-1.cor01-kent-syd.comindico.com.au (.217)  40.774 ms  36.718 ms  39.497 ms
 6  ge2-0.cw01-syd.comindico.com.au (.249)  38.375 ms  35.295 ms  39.097 ms
 7  ip-6..comindico.com.au (.6)  41.149 ms  38.711 ms  37.347 ms
 8  karl.planetmirror.com (.20)  42.275 ms  39.275 ms  38.410 ms

This means that if you are having problems browsing to certain sites, or sending or recieveing email, the problem is likley to be with the ISP itself, and have nothing to do with the DSL service Telstra provides. If you are having a problem logging on the the network at all, then this is when Telstra may be the cause of the problem. You can find out more about the Telstra Network from this Interoperabilty Testing Document. (mirror). This is 46 pages long, and some fairly heavy reading. There is also a similar 'DSL Service Interface Specification Document' (mirror). The documents are designed for CPE suplliers, but give a good idea of how the network works. There is also an unnoficial document written by a Telstra tech which explains some of their own troubleshooting methods (mirror)


A few words about L2TP

As of December 2001, Telstra began to allow ISP's to connect to its wholesale network using L2TP (Layer 2 Tunnelling Protocol). This change has no visible effect on the way the end user can connect or authenticate using PPPoE/A, It only effects the way the ISP connects with telstra on a layer 2 level.

Some ISP's have claimed that this makes the service more reliable. I cannot see any reason why this is the case. Data still passes through the telstra network (on a Telstra phone line, through to an Alcatel CMUX, on to a Nortel Shasta) where 99% of the current DSL problems lie. The ISP is the only real party to benefit from these changes. It allows the ISP to offer "true" dynamic IP's, "boot off" PPP users, and bill timed usage accurately etc, thus it gives the ISP more control, it does not give the end user any more reliablity. An excellent summary of the current situation can be found here

I have gathered some relevant infomation relating to how LT2P works. Known L2TP users are Ozemail and Internode. There are no known conflicts or issues for end-users who use an ISP that connects using L2TP.

About PPPoE

The majority of DSL connections are PPPoE. If you have an Alcatel ST Home modem, or a DLink DSL300, you need some PPPoE software, which can be found here:
  • RASPPPoE - For Win98/2K/Me
    • This is a free program that has been written for W2K. It intergrates itself within the 'Dial-Up Networking' component of windows. Installation and troubleshooting are easy. Although it does not run as a service, it can be configured to reconnect if disconnected. the RASPPPoE FAQ tells you all you need to know about installing and troubleshooting the software.
  • Enternet300 - For WinNT
    • This program runs within its own 'shell' and can be used on older MacOS's and well as Windows NT. It is not freeware, but trial software is available. Also available is a very informative troubleshooting FAQ
  • Roaring Penguin - For Linux (general)
    • This is GPL'd (free) command-line software, that works on (and comes with) most Linux distributions. It is highly configerable, intergrates well with pppd, and is easy to configure and run (2 steps). A basic bash script has been written which intergrates RP with Pacific Internet's back-up dialup service that will automatically cut over if the DSL goes offline.
  • Kernel based configuration - For real geeks
    • For Linux 2.4 - A complete guide to get this working within the linux 2.4.x kernel series. Written by Chris Collins.
    • For FreeBSD - Paul Hoadley has written an excellent guide to set it up for the Telstra network. .
  • MacOSX and WinXP (as well as the latest RedHat & Mandrake Linux) have native PPPoE support.
    • This means that the PPPoE software is built into the operating system, and configuration can be found as an option listed next to Dial Up options.
When you initiate a PPPoE connection, the session goes like this.

1 - [PADI] - PPPoE Active Discovery Initiation (client looking for Access Concentraitors)
2 - [PADO] - PPPoE Active Discovery Offer (the nearest AC responds with a service offer)
3 - [PADR] - PPPoE Active Discovery Request (the client decides on a PADO to respond to, and does so)
4 - [PADS] - PPPoE Active Discovery Session-confirmation (gives the ok session initiation)
5 - Session is Started by client (User & Pass)

This means that you should never have to try and configure or change any settings on the Alcatel Home, or DLink 200/300 yourself. The entire setup is done on the client software located on your server or PC.

Thanks to the Stallion EPipe debugger, we can see the PPPoE authentication process in action. This log refers to a failed authentication attmpts, but it shows us enough to see how PPPoE works. Also of intrest here is the CHAP reference to "" which is the default name/setting for ppp terminations at the Nortel Shasta

A correct PPPoE implementation can be seen in RFC2516

About PPPoA

PPPoA stands for PPP over ATM. I'm not going to start to get into ATM or various other protocols, as there is no visible difference to the end user. Most small basic routers (such as the Alcatel ST Pro, or the DLink 500) implement PPPoA. An internal (ISA or PCI) or external (USB) adapter provides the user (transparently) with an ATM interface (as opposed to an ethernet one for NIC/PPPoE). Due to the low cost of these devices, they are distributed or sold with many of the cheaper residential DSL packages ( Pacific Internet or Internode). Thus, many end-users will end up using PPPoA for the DSL connection.

Modems that need to use PPPoA:

  • D-Link DSL 200 USB Modem - Being used by Pacific Internet HomeDSL customers, and we have some information on how to set this up for a generic Windows-based installation. The USB drivers come on a CD with the modem.
  • Alcatel SpeedTouch USB. Currently being distributed by Netspace, for residential DSL. It has a very unique design, and is currently the only product on the market with Linux USB drivers.
In all instances, a PPP connection is made in the normal method of the operating system such as Windows' Dial Up Networking (DUN). No configuration should be done on the device itself. All that is required is to install the specific software drivers on the operation system of the PC. This sort of connection is not recommended for low-spec machines, due to the fact that they will draw power and resources from an already-drained host machine, and possibly interfere with the DSL connection.

Hardware Issues with D-Link 200 USB modems.
The D-Link 200 has some unconfirmed power management issues when used with some VIA motherboards. (inparticular, variants of the VIA VT8366/VT8233 chipset). The modem intermittently 'drops dead' with no lights, and no activity, a reinstall fails to find the modem, or the modem won't install, or be detected at all, or will be detected incorrectly). We believe the problem is some of the latest VIA USB controllers, they don't seem to be able to manage the resources required for a D-Link 200 USB modem. Its well known that the USB modems can use up to 80% of the bandwidth of a USB controller, but no other motherboard seems to have the problem.

Workarounds for this problem are

ADSLGuide, UK - Finding USB Bus Bandwidth
D-Link 200 FAQ. - Why DSL-200 stops responding after leaving it on for a while?
Microsoft KB - Windows XP Does Not Detect Your New USB Device
And some other issues are mentioned in this rough document (Thanks Polly M)

PCI-DSL Modem cards

Generic PCI DSL modem-cards are made by d-link and alcatel, and are the cheapest DSL modem overall. The fact that you have to open up your PC to install them seems to have limited their popularity a little. The only people I know that use PCI modems use them on Debian/GNU Linux boxes. The modem comes with a generic driver that provides a ethernet-style bridge (referenced as BRI1), and PPPoE is then used to terminate the connection.

Router information:

The following devices are known to use PPPoA to terminate a DSL connection.

  • Alcatel Speed Touch Pro - All setup information can be found here.
  • Cisco 827 - Intructions and a sample config - Done with Pacific Internet values, so you may need to substitute these. (Thanks Lalor).
  • Dlink DSL 500 - A correct PPPoA setup looks like this. The DSL500 is very configurable, and there are lots of nice things you can do with it. For more info see D-Link's support pages. The DSL-504 is a device with the same firmware, but with 4 extra ethernet ports, so it can act as a hub. (nice).
  • Netgear rt314 - A virtual web setup has been created, use the "Wizard setup" to configure the DSL account.
  • Netopia r6100 DSL Router - Support document by Paul Alexander
  • Nokia m1122 - Thanks to the people at iPrimus, who supplied this pppoa config for the Nokia dsl modem/router.
Some problems have been noted with Alcatels PPPoA implentation that appears to prohibit running a VPN through the PPPoA interface. I believe its something to do with the way the fort fowarding is set up. Despite many attempts, I have never seen this actually work, and would love somone to prove me wrong. There is also a Bigpond Direct document which has some interesting sample configs for various routers that may be of interest (mirror)

PPPoA is referenced in RFC2364. More PPPoA information is at Everything2.net (used as a reference).

Troubleshooting : No Linesync

On an Alcatel ST Home modem, there is a light called the "linesync", which is located second from the right-hand side. If this light is flashing, it means that the modem cannot locate the CMUX at the Telstra End of your DSL Line. A linesync issue is universal problem, regardless of how the DSL is configured on your phone line

Possible Issues

  • Phone Line - The first thing to check is to see if there is a dialtone on the phone line. Check cables, plugs, sockets, filters, other devices. This type of fault is usually hardware related. If you cannot hear a dialtone then you can speak with the Telstra faults center directly on 13 2999

  • Telstra Fault (a) Widespread - If a CMUX on the Telstra network is faulty, it will usually also affect other customers in the surrounding area. These faults are indiscriminate, widespread, but are usually rectified by Telstra within 6 hours.

  • Telstra Fault (b) Isolated Fault / Incorrect Provisioning - Other faults can be a little more obscure, and I have seen many caused by human error relating to Telstra Technicians. Telstra will also de-provision the DSL service from your phone line if you need to move it, change services, change billing details, or ownership of the line.

  • Encapsulation Type - If your modem is intermittently losing sync, or not syncing up at all (whilst other equipment will) check the line encapsulation type on the modem. The correct setting should be "Multimode" or "ANSI" (this is more or less an auto-detected setting) - or you may wish to set your modem to use "G.DMT", which is what Telstra uses.
In Short : A linesync issue is almost definitely a Telstra Issue, as your ISP usually does not have access to this part of the network. It is also something that can effect any DSL line, regardless of if it is provisioned as a type A, B, C or D

Troubleshooting : No Data on Authentication (no comms)

If your linesync is ok, but your PPPoE client reports a 'session-timout' or 'Time out while waiting for PADO' whilst logging on. We are encountering a different type of fault. It usually means the CMUX is ok, but the connection between the CMUX and the IPSN is not.

There are 3 types of faults here:

  • Check all the network cards involved, as well as any hubs, cables, other devices etc. Most NIC's have a green LCD light on them, that should be statically on to indicate the ethernet connection is working on a hardware level.
  • Widespread Telstra Outage - Failure of Access Concentrator. If this is beeing rebooted, or under maintenece, then usually the majority connections across your entire city/state will also fail. Because this will affect a vast ammount of clients, Telstra and associated ISP's usally post notage of this, and you may be able see this information on their tech websites (Telstra & Pacific) Such faults usually last for under 30minutes, and the worst example of this was one that lasted for 6 hours.
  • Single Telstra Fault - Data Lockup. This mostly affects PPP-based customers. Sometimes, for no good reason, the 'data tunnel' between the CMUX and the IPSN will corrupt itself. The 'tunnel' is how they refer to the PVC that forwards all your traffic from your CMUX at your local exchange out to the IPSN. Telstra's solution to this ongoing problem is just to break and re-establish this link, generating a new PVC from the IPSN to the CMUX. Your ISP will have access to your PVC identifier, and this will change when the 'tunnel reset' happens. If your connection 'locks up' when there are no known outages on the network, your ISP should request a rebuild straight away. These may take around 24 hours for Telstra to perform. (acronym overload?)

    So why do these happen? The best answer I have seen to this was provided by a current telstra helpdesk staffer in a series of emails, and fit in with the what most ADSL support people are observing when dealing with Telstra

    PPPoE is a dodgy protocol, broadcast protocols running through it it, like udp and such, can cause the ppp session to lockup and reset. This disconnection of the pppoe session should not however cause a problem with the tunnel. Blame nortel, or alcatel, or telstra, or all three, maybe even the easter bunny as well. Probably nortel though, the atm pvcs lack of traffic flow is most likely caused from the IPSN end of thing, as it provides you the ppp session.

    - Borderline attenuation problems (usually with downstream), this also accounts for customers going in and out of sync alot and that causing ppp sessions to die, this repeatedly disconnected thing sees a higher frequency of the tunnel dying.

    - cmux problems, don't know the cause, [Telstra] will sometimes initiate the software being reloaded onto the cmux, sometimes the cmux port is swapped for customers that get alot of tunnel problems. But pretty much telstra have stopped blaming alcatel for the tunnel problems, it is still under 'investigation' by Nortel and Telstra technicians.

    - as i was saying with udp based things, saturating upstream with these type of things, when your machine is trying to send out to many packets, that really increases the likely hood the ppp session will die and the tunnel too. for example, 512/128 customer, running a quake3 server ( I don't know why, but they do) - 4 other people connect in with rates of 5000+ - bam.

    - PPPoE clients, seems to happen with all pppoe clients, however, in regards to things like broadcast protocols saturating your bandwidth, we tend to see OSs with better tcp stacks handle things better. Linux/rp-pppoe tends to get alot less of these types of issues, where as win98/ME are culprits. Probably the send-q handling, I dunno really.

    This also raises the possibilty that these data lockups could somehow be 'engineered' as a form of Denial of Service attack against a particular user, although I have never seen any evidence of this. Another application that is known to cause problems with PPPoE is the Microsoft "Netmeeting" program.
In Short: It would seem that this part of the Telstra network/infrastructure is inherantly faulty at this level. There has been some some interesting discussion and observations made already with regards to the Nortel Shasta and its capabilties in handling a large DSL Network. Officially, Telstra have never even acknowledged that this issue exists, and this would seem to be the first step involved in solving the issue, to avoid a general migration away from their wholesale network by their largest customers.

Troubleshooting : Other Issues

  • Slow Speeds - These are not usually DSL related, (I have never had any capacity issues on my line) however, and easy way to test is to do an FTP transfer from your local ISP's mirror server (Pacific) On an stand-alone connection you should be able to get these speeds
    • 256/64 = above 20KBytes p/s
    • 512/128 = above 40KBytes p/s
    • 1500/256 = above 120KBytes p/s
    Your ISP can investigate if Telstra have provisioned the line at the correct speed (or some modems will tell you) or the line is running at a high capacity. Telstra can see if the DSL service is taking up more than 50% of total line usage. This is usally tested before the line is provisioned to avoid this situation


  • MTU (Maximum Transmission Unit) related issues (should) only occur when using PPPoE. Common symptoms of this is very slow performance, problems FTP'ing and some webpages just not coming up for no particular reason. The reason these issues occur is to do with an inherent flaw in the way PPPoE works as a protocol Fenn has written about how these problems happen, and how to work around them. This document from DSL reports provides some tests you can do to see if MTU is the cause of these problems
  • Alcatel Modems have some terrible security flaws (mirror)
  • Be sure to check sites like Whirlpool, CableGuy & Ausforum for current discussion about new troubleshooting, problems, tricks & tweaks.

  • Issues like speed and constant dropouts can be caused by the DSL, but they are just as likley to have nothing to do with it. Be sure to check everything - phone lines, extention cords, protocols, modems, sockets, plugs, dust, switches, software, hardware, your operating system, etc. Your ISP will only speak to telstra about the issue when they are sure that its not anything else thats causing the problem.


A Type B Connection is a pure Bridged Ethernet connection between you and Telstra

This is the type of connection I enjoy using at home. In my opinion its the most simple, reliable and trouble-free DSL connection available (Its also slghtly fast as there is no PPPoE involved). Pacific Internet do these type of connections for some corporate customers. Most ISP's will not do this for a residential account because of the 2 IP address's that are wasted making the connection.

A typical TypeB connection looks like this:

Type B Diagram

The configuration for this is done on your NIC. The settings are:

W2K : Start => Control Panel => Network & DUconnections => rightclick = Properties => TCP

IP Address : One from your allocated network
Default Gateway : Telstra End GW
NetMask : Your allocated Netmask (eg .252 for 2 usable address's)
DNS : Your ISP's settings

These settings should be given to you by your ISP.

My own connection was done on a RedHat Linux box, and I have documented the results. The good thing about these connections is that they do not suffer from 'data lockups' like PPP connections do, as there is no authentication process. I have experienced 99.99% uptime with this configuration.

Troubleshooting : No Linesync

  • A linesync issue is the same with any type of DSL-enabled phone line, regardless of how this line is provisioned. The tips of have already outlined will apply here also.
Troubleshooting : No Data Transfer (no comms)
  • Check all the network cards involved, make sure each NIC is responding. From the machine directly connected to the DSL modem, you should be able to ping your Telstra gateway address (and anything else). if this request "times out" it could be an indication that Telstra's Access Concentrator is offline completley. Your ISP is the only other party that has the abilty to ping that gateway, and this is the first thing a helpdesk rep will check.

  • If you can ping the telstra gateway, but recieve networking-based errors on other external IP address, then we need to double check your routing table and your ethernet interface configuration. The command is 'route print' (you should see a default gateway here, with the IP address of and ipconfig (ifconfig on a linux box) which will show the gateway for each interface. My 'ifconfig' looks like this

    eth0      Link encap:Ethernet  HWaddr 00:10:4B:79:C4:30  
              inet addr:.202  Bcast:.255  Mask:.252
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:79966 errors:0 dropped:0 overruns:0 frame:0
              TX packets:77873 errors:0 dropped:0 overruns:0 carrier:0
              collisions:1 txqueuelen:100 
              RX bytes:45481255 (43.3 Mb)  TX bytes:13608460 (12.9 Mb)
              Interrupt:10 Base address:0xde00           

    And my route table looks like this. (ADSL.mel is the Telstra gateway, default is the same as

    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    .200  *               .252 U     0      0        0 eth0       *            U     0      0        0 lo
    default         ADSL.mel.pacifi         UG    0      0        0 eth0

    In Short : we need to ensure that
    a) You PC can identify your network interface. (hardware detection)
    b) Your network interface can idenitify itself, and the network that it is apart of. (interface config)
    c) You network needs to have a place where it can send data to other networks. (routing table)

This type of conection forms the base of a Type D configuration. A Type D will attempt to build on your current setup, using your current bridged ethernet to route another network down the DSL line.


A Type C Connection is a way of routing networks down a DSL line using a router device

These connections must be made using a DSL modem/router. The have been tried and tested on an Alcatel SpeedTouch Pro only, although they should work on most Cisco routers and the D-Link DSL 500.

A routed connection looks like this.
Type C Diagram

On your router, you need to:

(a) Configure your WAN interface with your User-End IP address, and set a gateway as your Telstra-GW. Set an appropriate subnet mask (Pacific Internet allocate a /30 for these connections, so a subnet mask would be .252). From this point you should be able to ping the Telstra Gateway without any hassle

(b) Configure the route for your network, as your network will travel "through" the frame we have just created.

(c) Configure the router with another IP address, taken from your network. (Most people choose the lowest ip)

(d) Allocate another IP address to a client machine on your network, and set the gateway as the network IP you have just given your router.

(e) Make sure the router can see both subnets. From your router you will be able to your Telstra GW, and your client machines should be able to see the rest of the internet

This style of configuration differs between routers, as do the troubleshooting methods. At the moment 3 modem/router devices are supported. Aside from what I have mentioned here, I have been told by third partied that the Netopia r1600 will work with this configuration, as will the iprimus-supplied nokia's.

  • Alcatel Speed Touch Pro - I have written explicit documentation on how to set this up.
  • Cisco827 - Command setup and running config
  • D-Link DSL500 - The out-of-the-box 500 series does not come with full cip/ipoa support. The firmware inside the modem needs to be upgraded. The firmware was only released in January 2002, and it can be found here. The firmware is labelled"DSL-500R201b5AU.exe". There is also firmware available for the 504, but from what I am told, the only real difference is in the labelling.
Troubleshooting : General
  • See here for 'no linesync' troubleshooting

  • To establish that there is a 'no data' issue, attmpeting to ping your Telstra gateway from your router. If it does not return a ping then it could mean that Telstra's end is completley offline. At this point it may be a good time to ring your ISP to get confirmation.

  • This following advice comes from Lee DeSouza of Pacific Internet's DSL provisioning department

    For a new (or modified) connection, easiest way to tell if it's misconfigured (or rather, a dead giveaway) in terms of mode (IP over ATM vs Ethernet) is to ping the customer and get them to watch the line rx / adsl act light... if it appears to blink once a second (ie: in time with a constant ping once per second) but you get no reply - it's probably provisioned wrong (or of course, the other issue would be the cust not correctly setting routes).

    Naturally, for a customer requiring a config D that actually (incorrectly) has a C, the access concentrator sends ATM-encapsulated cells to the end-user, to which the Ethernet device on the customer end has no clue what to do with. And vice versa.

The only other real point of failure is the router itself. I have seen that the SpeedTouch Pro needs to be rebooted on occasion, for no apparent reason. The first thing to check in any instance is the route table - make sure its the same as when you left it.

The reason that there is not much documentation for this type of connection is because the user has full control over what is done with his or her network. All telstra do is provide a gateway for you to send data to, the rest of the configuration is done on your router. For further troubleshooting with the ST Pro, I suggest you read my config document


A Type D Connection uses bridged ethernet to route additional networks on a DSL line

The first thing to understand is that a Type D configuration is an extention of a Type B. With a Type B, a fairly straightfoward Bridged Ethernet connection is established. A Type D uses this connection to route more networks down the DSL line, in a similar fasion ot a Type C.

You can utilise this connection with any PC that has more than 1 network interface. It looks like this.
Type D Diagram

You should have been allocated your End-User address and gateway address by your ISP. You will need to configure the network card appropratley, and then ping the GW end. Assuming that you get a response from the gateway, you can proceed to configuring the second network card with an IP address from your allocated range.

A customer set this up on his debian box, and emailed me to tell me how he did it

Troubleshooting : Networks

  • If the linesync light is flashing, see here.

  • Before reading anything else, get an idea of how to do some troubleshooting for the Bridged Ethernet
    This has been taken from the Type B Config, as we need to make sure the same bridged ethernet configuration is working before we move on to testing the routed config. Some ISP's allocate internel IP ranges to make up this first part, and you shouldnt need to treat these any differently to public IP space.

  • As with all network connections, check all the network cards involved, as well as any hubs, cables, other devices etc. Most NIC's have a green LCD light on them, that should be statically on to indicate the ethernet connection is working on a hardware level.

  • Now see if you can ping the telstra-end gateway given to you by your isp. If this is down, then their is a high possibility that the Telstra IPSN is completley offline. If this is a new connection make sure you clarify the gateway details with your ISP - its also possible that Telstra have configured this incorrectly

  • Your ISP can run a test to make sure the line is provisioned with a "Type D" and not a "Type C" or other configuration.

  • Provided you can ping the GW successfully, but are having problems pinging elsewere, the routing table is most likley going to tell you whats wrong with the connection. I have drawn up a standard one here, as seen from the server machine. It assumes that .0/24 is your network, .200/30 is the bridged ethernet. (.201 is the Telstra GW) The command is 'route print', (from the CLI) and this table format may vary slightly between windows/linux/bsd.

    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    .200  *               .252 U     0      0        0 eth0
    .0 *               .0 U     0      0        0 eth1       *            U     0      0        0 lo         .201         UG    0      0        0 eth0

    Interface eth0 should have the IP address of .202 (network card connected to DSL modem)
    Interface eth1 should have the IP address of .1 (network card connected to your LAN)

    The routing table on a client machine is a little more simple. It also assumes that you choosen given the lowest IP on your network to be second NIC on your server, and this is the gateway for the client machines.

    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    .0 *               .0 U     0      0        0 eth0       *            U     0      0        0 lo         .1         UG    0      0        0 eth0

    As with a Type B, we need to ensure that
    a) You PC can identify your network interfaces. (hardware detection)
    b) Your network interface(s) can idenitify themseves, and the network that they are apart of. (interface config)
    c) You network needs to have a place where it can send data to other networks. (routing table config)

Once these connections are set up correctly, I have never seen them change dramatically, to the point where they need serious troubleshooting. This is simple ment to give you an idea of how the setup should work.



Other Links and resources of use.
  • The Cable Guy - Excellent resource site for tweaks / troubleshooting, tips and problemsolving for all types of broadband connections.
  • Whirlpool - Broadband News Site - also check out the forums for discussion and ISP reviews. Also home to the Australian Broadband FAQ
  • BroadBand Choice - Lists australian ISP's, shows benfits, of each ISP compared
  • AusForum - Broadband Users discussion site, topics range from DSL, Linux, Cable, Gaming and everything else. Very busy site.
  • - Newsgroup based around ISP discussion and access problems.
  • Becsta's Linux-ADSL guide - Informative Linux/DSL/Bigpond FAQ
  • DSL Reports - US-based site with the latest DSL tricks and tweaks
  • ChasmS - Contains virtuals machines for remote DSL troubleshooting
  • Greystorms DSL Page - For using ICS software to share your DSL connection
  • adsl.cutw.net - My own DSL-info dumping ground
  • Pacific Internet Software Mirror - Where I get all my software from locally

Definition of Terms & End Notes.

I gathered some of these terms from this document. A complete definition of terms can be found here

ADSL = Asymmetric Digital Subscriber Line
ATM = Asynchronous Transfer Mode
CMUX = Customer Multiplexer
CPE = Customer Premesis Equipment
DAC = Digital to Analog Converter
DSLAM = DSL Access Multiplexer
IPSN = Internet Protocol Services Node (also known as TAS / Access Concentrator)
LT2P = Layer 2 Tunneling Protocol
MTU = Maximum Transmission Unit
NIC = Network Interface Card
PPPoA = Point-to-Point Protocol over ATM
PPPoE = Point-to-Point Protocol over Ethernet
PSTN = Public Switched Telephone Service
PVC = Permenent Virtual Circuit

This Document is to help you troubleshoot your own DSL connection, but it does not come with any warranty or liablity. It is yours to play with. Any opinions conveyed in this document are mine, and not that of any other persons, including my employer. This document may be freely distibuted so long as it is not used for profit, or modified in any way.

This document was written by myself, using the knowedge gained from working at Pacific Internet (Australia). This document has ended up being more detailed and complex than what I first set out, so most lilkey I will be writing an abridged, less-technical version at some stage. This document would not be here without the help of people like Byron Brink and Fenn Bailey, and the technical staff at Pacific Internet. I am also greatfull for the help and information contributed by some unnamed techincal staff at Internode, Telstra, and iPrimus.

Revision 1.3 12/06/02 | Changelog | Access Logs
Please send errors / questions to james [at] pacific.net.au
(c) James Mollison


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