Weird Half-Bridging / DHCP Issue with Linksys AM300 RESOLVED

Forums › New Zealand Broadband › Weird Half-Bridging / DHCP Issue with Linksys AM300 RESOLVED

SamF

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#17236 18-Nov-2007 19:27

[Moderator edit (TH): Resolved. See this thread for details]

I have the following setup:

Linksys AM300 ADSL Modem in Half-Bridge Mode
Linksys WRT54GL with DD-WRT v23 SP2 installed obtaining the external IP from the ADSL modem
X-Net ADSL Connection with dynamic IP

Previous to this week, this setup ran flawlessly until a couple of days ago it stopped working properly.

What is happening is that the modem is connecting fine & picking up the assigned Internet IP, Subnet and Gateway addresses as normal and connectivity from the modem works fine. Also, the DHCP on the modem works (to a point) and the router picks up an IP address, subnet and gateway from the modem. However, while the modem is getting a subnet mask of 255.0.0.0, the router picks up a subnet of 128.0.0.0!!??

The only thing that has changed is that previous to last week, X-Net were giving out 58.x.x.x ip addresses, and a 58.x.x.x gateway address. However, as of this week, I am getting a 118.x.x.x ip address and a 58.x.x.x gateway, which is a little odd.

I'm wondering if somehow this is screwing up the DHCP on the modem and causing it to serve up an incorrect subnet mask to the router?

I think there might be a bigger problem however as even if I manually specify the correct IP details on my modem (& don't use DHCP), it still doesn't work (unless half-bridging requires DHCP in some way that I don't understand).

I tried obtaining IP details from the modem with my PC and I get the same result, so I don't think the fault lies with the router. I have tried resetting the modem to factory defaults and configuring it again from scratch to no avail. I am also running the latest firmware that I can find (1.19.02).

I've setup double-nat at the moment, which works ok, but is not what I want in the long term.

I've tried creating a post on the Linksys community forum, but for some reason it won't let me create a new post!

So, does anyone have any ideas?

Cheers,

Sam.

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#95897 19-Nov-2007 11:34

Here's a screenshot someone else took:
http://img405.imageshack.us/my.php?image=halfbridgeek6.jpg
Note the differing subnet masks between the AM300 (255.0.0.0) and the WRT54GL (128.0.0.0 in this case running Tomato) - as you have mentioned. This difference is not evident on my Dynalink RTA230 (in half-bridge) + WRT54GL setup, and nor is it present on other Dynalink devices some friends have - indicating the fault is most likely a firmware issue on the AM300 :(.

barf

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#95906 19-Nov-2007 12:09

thats interesting, my half-bridge setup at home dropped off. I'm with Xnet too - this happened on Friday but i'm in wellington atm so can't check it out until I get home. also somewhat interesting, I got a static IP but, they changed the IP without telling me. make sure you try another router too.

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SamF

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#95908 19-Nov-2007 12:26

Ahah! So I'm NOT loosing it

Hmm, curiouser and curiouser!

So this DOES seem to be an issue with X-Net's recent IP changes & AM300 half-bridging then. I think that it is quite unusual to have a gateway ip that is in a different subnet to your assigned IP, & maybe the AM300 just can't handle it!?

So Frio, which post did you get that image from?

I've e-mailed Linksys support about this btw & I'll let them know that this issue is widespread. I'll also post any replies I get in this thread.

Lorenceo

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#96148 20-Nov-2007 22:22

I've been having problems with this too. Emailed Linksys support, no reply as of yet.

SamF

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#96149 20-Nov-2007 22:24

Neither, slackers. Might try via my retailer and see if they have any back channels they can use...

SamF

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#96451 22-Nov-2007 19:42

Called the reseller I got my AM300 from today and asked if they had any channel support for Linksys products. They didn't, and gave me the linksys 0800 support number (0800 800 015 FYI).

I rang and went through the normal 'yes, updated my firmware. Yes, reset modem to defaults' etc, but they wanted to replace my modem until I told them that there were a number of people having the same issue with this modem. After a bit of convincing I eventually managed to get the call escalated to the software engineers as a firmware issue!

I'm not sure how long this process will take, but I intend on chasing it up once a week.

They were also interested in looking at this thread, so if everyone having the issue can post their details (ie; modem firmware & setup) & that they are having the same issue as me, then it will probably help push our case up the priority queue.

SamF

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#96456 22-Nov-2007 19:58

Oh, I keep forgetting to mention. I posted this issue on the DD-WRT forums as well and I got a rather odd reply.

One guy said that I should turn bridging on, and DHCP off!!?? I can't see how this would work myself! Can anyone enlighten me on this? Maybe he was referring to FULL bridging?

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SamF

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#96471 22-Nov-2007 21:32

Thanks to Frio & also Google, I found 2 more threads on different forums about this issue:

http://forums.overclockers.co.nz/showthread.php?t=27651

http://www.gpforums.co.nz/showthread.php?s=&postid=4631533

I've posted a message on each of them asking everyone to post their details in this GeekZone thread so that we can get details from as many people with the same issue for Linksys to see.

Ragnor

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#96493 23-Nov-2007 01:56

frio: Here's a screenshot someone else took:
http://img405.imageshack.us/my.php?image=halfbridgeek6.jpg
Note the differing subnet masks between the AM300 (255.0.0.0) and the WRT54GL (128.0.0.0 in this case running Tomato) - as you have mentioned. This difference is not evident on my Dynalink RTA230 (in half-bridge) + WRT54GL setup, and nor is it present on other Dynalink devices some friends have - indicating the fault is most likely a firmware issue on the AM300 :(.

Yeah that's my screenshot, I also emailed the au/nz support email about a week ago, recieved an automated response and that's about it. Didn't get around to ringing the 0800 number.

My setup is:
AM300 1.19.02
WRT54Gl
PPoA Half Bridge

As evident by the screenshot the external IP address assiged by my ISP is on a different subnet to their default gateway, the AM300 passes the wrong subnet mask via dhcp to the router.

Lorenceo

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#96739 24-Nov-2007 18:31

Just got a reply from Linksys tech support.
Put a link to this thread in the email.

When I have my AM300 in half bridge it reports the IP address and Gateway IP correctly, but the subnet mask is wrong.
No traffic passes through when it does this, I can't even access the modem's status page.
An example of what the modem reports to the router in half bridge:

IP Address	118.90.11.198
Subnet Mask	128.0.0.0
Gateway	58.28.15.31

Let's hope that a solution is on its way.

SamF

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#96741 24-Nov-2007 18:35

So that was a 'real' reply as opposed to an automated 'we got your e-mail' message?

Lorenceo

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#96749 24-Nov-2007 19:49

Yeah, there was an auto reply thing too.

SamF

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#96763 25-Nov-2007 00:18

STILL haven't got a reply to my e-mail enquiry eh...

BTW, a good workaround (in case anyone hasn't done this already), is to disable the bridging on the modem, set the router to a static IP (on the modem's subnet) & then forward ports 1-65535 to the ip address of the router.

This is a double NAT setup which effectively bypasses the firewall on the modem. Works ok as a stand-in solution for now.

If anyone needs more detailed instructions, just let me know.

SamF

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#96816 25-Nov-2007 12:23

Just got a reply from Linksys from my original e-mail support query!!

Dear Sam,

I personally apologize as this reply has already gone beyond the promised 24-hour response. Due to unforeseen circumstances we are having difficulty meeting the promised time. We are doing our best though, to ensure that you receive the service you deserve.

I understand you are having problems with the AM300 set to half-bridge mode. I would be glad to assist you regarding it.

Based on your description of the problem, your ISP probably altered settings at their end causing the changes in your IP address and subnet mask. The AM300 only receives whatever IP address, subnet mask, and gateway values they assigned and passes them on to the router.

I have a solution for you that will help avoid double-NAT in your network. It will also make the router receive the IP address, subnet mask, and gateway values accurately. I suggest you set the AM300 to full bridge mode (by selecting Bridge Mode Only as its Encapsulation) and the WRT54GL to PPPoE. This way, the AM300 becomes a pass-through device and the WRT54GL receives the IP address, subnet mask, and gateway directly from your ISP via PPPoE.

Please let me know if this solution fixes the problem.

Sincerely,

Leo
Badge ID 25561
Email Technical Support
Linksys® – A Division of Cisco Systems, Inc.
Website: www.linksys.com/support

I've e-mailed him a response explaining that I can't use PPPoE.

Lorenceo

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#96829 25-Nov-2007 13:56

Yeah, I just got a similar reply from the same person.
I asked him to pass this issue on to the technicians, so that they can look at it and update the firmware accordingly.

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