Modem to replace the SR204

[metcat7]

Hi,

I have an SR204 modem-router, and a Ubiquiti Dream Router.

I want to use the Ubiquiti router without double-NAT. From what I understand, this is not possible with my current devices, because:

• The Sky router doesn't support bridge mode, so I can't use it as a modem.
• The Ubiquiti router doesn't support the authentication scheme it would require to replace the Sky router.

I want to keep the Ubiquiti router, and replace the SR204 with a modem that is compatible. What are my options for this?

What I've found on forums so far is that the SR204 uses a G.Fast connection, and authenticates with DHCP Option 61 MER. If I buy a G.Fast modem to replace the SR204, does that already take care of authentication, or would the router still need to authenticate?

[Chrisee]

@metcat7 if you have the SR204 as opposed to the SR203 it implies you are on a G.Fast service ( Ultrafast over copper as oposed to fibre to your home) so a standard VDSL modem wont work. G.Fast being more rare means there are not many around. Draytek had a model and I assume there maybe others but they will be pricy. 

[Skull+Treaty]

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@metcat7 wrote:

If I buy a G.Fast modem to replace the SR204, does that already take care of authentication, or would the router still need to authenticate? The authentication is needed at router level, not the modem. 

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@metcat7 

[metcat7]

Thank you, that's useful!

I found some forum posts that since version 1.7.0, my router should support DHCP Option 61. If that is the case, then this should work:

1. Update the firmware on my Ubiquiti router.
2. Replace the SR204 with another G.Fast modem, probably the Draytek V166-K (costs 130 GBP). This is acts as a bridge between the G.Fast network and my local Ethernet network.
3. Configure the Ubiquiti router to authenticate via DHCP Option 61, with the credentials I'll find on the wire when I sniff it while my SR204 router is rebooting.

I'll report back if I don't forget.

It sure is a lot of work and money to get rid of this router!

[metcat7]

It worked. I'll describe the step-by-step below for anyone who would want to use a Ubiquiti Dream Router and replace an SR204 (must also work with other Ubiquiti routers, but it's the one I used). I replaced the modem with the Draytek V166-K.

1. Get your DHCP Option 61 username/password from the wire. Some posts on this forum claim that this is not necessary anymore, but I did it anyway. You can find youtube videos on how to do this, I recommend the Wireshark filter: dhcp.option.type == 61
2. If your Ubiquiti router is running an old firmware, update it now so it has the option to authenticate with DHCP Option 61. Plug it in to your SR204, go to its config UI, update the Network application.
3. Remove the SR204, and instead connect the Draytek modem. Connect your computer to it with Ethernet. For me the modem was not running a DHCP server so it didn't give me an IP, follow the manual to set the right IP manually and connect the modem. Make sure there is a physical connection to the ISP, change the admin password.
4. Connect your Ubiquiti router to the Draytek modem, and connect the computer to the Ubiquiti router. Change the computer config back to receive the IP from the router dynamically, connect the Ubiquiti router.
5. On the Ubiquiti router UI open the Network app, go to Settings, Internet, open the WAN connection and switch to Manual config. Go to DHCP Client Options. Select Option 61, and add the value you copied from the wire. For me the username and password were separated by a pipe (|) on the wire, so here I used the same format.

[simon194]

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@metcat7 wrote:

Thank you, that's useful!

I found some forum posts that since version 1.7.0, my router should support DHCP Option 61. If that is the case, then this should work:

1. Update the firmware on my Ubiquiti router.
2. Replace the SR204 with another G.Fast modem, probably the Draytek V166-K (costs 130 GBP). This is acts as a bridge between the G.Fast network and my local Ethernet network.
3. Configure the Ubiquiti router to authenticate via DHCP Option 61, with the credentials I'll find on the wire when I sniff it while my SR204 router is rebooting.

I'll report back if I don't forget.

It sure is a lot of work and money to get rid of this router!

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You could have saved some money by getting hold of a Huawei MT992, the modem Openreach used to supply for G.Fast installs. They usually sell for between £40 - 60 on the bay of e's and is preconfigured so just needs to be connected up.

[DerbyDave]

Hi @metcat7 ,

Can you confirm this is a UDR, not UDM? I've been wanting to swap from an older Vigor unit to a UDR and reached out to Ubiquiti support re. Option 61. While waiting for an answer, I saw your post so ordered the UDR, support have now got back to me to say only Option 40 & 60 are supported. I'm hoping they misunderstood and are talking about the LAN side!

[metcat7]

Confirmed, it's an UDR. Dream Router, not Dream Machine.