Bridged modem PPPoE VPI/VCI options

Installing and Using OpenWrt Network and Wireless Configuration
1

My internet connection is provided via ADSL, and my ISP specifies PPPoE for the DSL connection. They also provide values for VCI/VPI, and this configuration works fine with my Netgear DM200 modem in stand-alone mode, using stock firmware.

When switching the modem to bridged mode and supplying the PPPoE config from my OpenWRT router, there is no option to supply values for VCI/VPI when the router's WAN interface is configured for PPPoE.

I understand that these options are more commonly associated with PPPoA encapsulation, so does it even make sense to use them with a PPPoE connection? I've tried configuring the WAN interface using PPPoE and PPPoA, but both fail to establish a connection.

Cheers,
Jon

2

VPI/VCI should be configured on the modem, that has no relation to OpenWrt.

2 Likes
3

Take a look at the system log as there should be output of the futile connection attempts, potentially yielding a hint of what is not working. For more verbose ppp output add in /etc/config/network

config interface 'wan'
	option pppd_options 'debug'

and apply changes with ubus -v call network reload

4

Are you using the DM200 with stock firmware or OpenWRT firmware?

The stock firmware is quite lacking and bridge mode is actually only half bridge, you still need to input the VCI/VPI settings on the DM200.

With OpenWRT on the DM200, this issue goes away

1 Like
5

Here's the debug output from pppd. It seems to make three connection attempts before giving up after they time out. Is there anything to be learned from these log messages?

Thu Jul 16 20:27:47 2020 daemon.info pppd[14559]: Plugin rp-pppoe.so loaded.
Thu Jul 16 20:27:47 2020 daemon.info pppd[14559]: RP-PPPoE plugin version 3.8p compiled against pppd 2.4.7
Thu Jul 16 20:27:47 2020 daemon.notice pppd[14559]: pppd 2.4.7 started by root, uid 0
Thu Jul 16 20:27:47 2020 daemon.debug pppd[14559]: Send PPPOE Discovery V1T1 PADI session 0x0 length 12
Thu Jul 16 20:27:47 2020 daemon.debug pppd[14559]:  dst ff:ff:ff:ff:ff:ff  src xx:xx:xx:xx:xx:xx
Thu Jul 16 20:27:47 2020 daemon.debug pppd[14559]:  [service-name] [host-uniq  00 00 38 df]
...
Thu Jul 16 20:28:02 2020 daemon.warn pppd[14559]: Timeout waiting for PADO packets
Thu Jul 16 20:28:02 2020 daemon.err pppd[14559]: Unable to complete PPPoE Discovery
Thu Jul 16 20:28:02 2020 daemon.info pppd[14559]: Exit.

If the only solution is to flash OpenWRT onto the modem, then that's what I'll have to do. However, I'd rather avoid that, given that it should really be a set-and-forget device. I shouldn't need all the extra features that OpenWRT gives me, just for a stand-alone modem.

Once in bridged mode, the DM200's menus to configure the PPPoE settings are disabled. If it retains the config previously entered in router mode then it should work, as I haven't changed the VPI/VCI settings.

6

You don't need to configure PPPoE on the modem, that still has nothing to do with OpenWrt.

7

What I meant was, when the modem is in bridge mode, it doesn't offer the ability to configure the connection at all, including VPI/VCI.

8

that has nothing to do with OpenWrt

9

Can you explain why this is the case, other than the fact that OpenWRT doesn't provide an option to pass these values to a bridged modem?

10

VPI and VCI are attributes of ATM connection that goes from ISP's DSLAM to xDSL CPE, not further.
Modem in [full] bridge mode commonly uses RFC1483 bridged LLC encapsulation to transfer Ethernet frames across ATM connection (defined as a combination of VPI and VCI).
Your router is talking only Ethernet or Something-over-Ethernet to the external world, ATM layer (as well as all ATM attributes like VPI/VCI) is completely hidden to the router.

11

Thanks for the explanation. So, if the modem doesn't retain the encapsulation settings when switching to bridged mode (I'm not actually sure this is the case), then what I'm trying to achieve won't be possible with the stock firmware.

If I install OpenWRT on the DM200, will it then be able to operate as a fully bridged modem, while allowing the configuration of VPI/VCI in the LLC encapsulation settings?

12

Yes, this is what I read here: https://openwrt.org/toh/netgear/dm200#bridged_mode_with_openwrt
According to the example provided there, you will need to create a bridge between VPI/VCI and a VLAN, then on your main router you will need to configure PPP-over-Ethernet-"over VLAN".

13

Those are DSL options not PPPoE

You need to read the manual for the DM200 and workout out how to set them up in bridge mode.

Read page 69 of OEM manual

IMPORTANT:
After you disable the modem’s routing features and the modem functions as
a DSL modem only, you can access the modem only through a fixed IP address,
which is 192.168.5.1.Therefore, make sure that IP address 192.168.5.1 is not
assigned to another device on your network.
To disable the modem’s routing features and configure the modem as a DSL modem only:

  1. Launch a web browser from a computer that is connected to the network.
  2. Enter http://www.routerlogin.net.
    A login window opens.
  3. Enter the modem user name and password.
    The user name is admin. The default password is password. The user name and password are
    case-sensitive.
    The BASIC Home page displays.
  4. Select ADVANCED > Advanced Setup > Device Mode.
    The Device Mode page displays.
  5. From the Device Mode menu, select Modem (Modem only).
    By default, the selection is Router (Modem + Router).
  6. Click the Apply button.
    Your settings are saved. The modem restarts.
    You can now access the modem only through a fixed IP address, which is 192.168.5.1.

So make sure you connect your computer directly to the modem and give your computer a static IP such as 192.168.5.2

1 Like
14

Unfortunately, that is not possible:

15

Sorry it seems to be a bug.

https://community.netgear.com/t5/DSL-Modems-Routers/DM200-in-ADSL-modem-only-mode/m-p/1602752

1 Like
16

As mentioned previously, VPI/ VCI are a modem-side configuration, which needs to be possible for proper ADSL operations (according to your ISP's requirements). All the xDSL modems I've dealt with so far have offered this setting.

Running OpenWrt on the DM200 is possible and would offer these options.

1 Like
17

Thanks everyone for your replies. I now have a much better understanding of the delineation between settings that can be passed from the router, and those which must be configured on the modem. With confirmation of the config issue in the DM200, everything makes sense now.

1 Like