Modem random drop-outs

[#1]

Connection: FTTC VDSL 2

Router: Asus RT-AX58U with OpenWRT - standard set up, nothing special.

Modem: Huawei HG612 with latest Kitz forum reflashed firmware

Discussion: System, which is recent install, works fine most of the time, I'm getting full throughput compared to my old FritzBox, which worked for years but showed signs of giving up, hence the new hardware. DSLStats reports no problems. This problem manifested itself from the beginning of the new hardware's installation.

Problem: Randomly, the link between modem and router seems to fail, for just ten seconds or so while the router re-authenticates. It looks like a problem with the line card as authentication takes a fairly short time, while retraining takes much longer - and it's not doing that.

Fixes tried - all made no difference:

• New router
• Replacing the Ethernet cable
• Re-orienting the modem to allow for better heat dissipation

Suggestions welcome, please!

[#2]

In the absence of helpful router stats, given that you have seen similar with different kit - consider REIN n SHINE.  See Kitz.

[#3]

@mdubash 

Randomly, the link between modem and router seems to fail, for just ten seconds or so while the router re-authenticates. It looks like a problem with the line card as authentication takes a fairly short time, while retraining takes much longer - and it's not doing that.

Are you absolutely sure the modem isnt retraining ?

If you are, then check the openwrt kernel log for the WAN ethernet port (eth<n>) status. You may see something like

[9086704.622979] mtk_soc_eth 1e100000.ethernet eth0: Link is Down
[9086717.102934] mtk_soc_eth 1e100000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off

I had a similar problem with a Mediatek chipset based router. It would occasionally 'glitch' and drop the eth port and then immediately recover. Problem was it would cause the pppoe to drop. I fixed it by setting 'force link' on the advanced settings for the WAN interface. In that way it won't drop PPPoE due to a short 'carrier' ( the eth<n interface ) drop but if connection is lost for any length of time then PPPoE will time out due to LCP echo not received.

For info, I have LCP echo threshold set to 6 and LCP echo interval set to 5, so a 30 sec timeout in total

[#4]

Thanks for the feedback. Here are the DSL stats (no errors):

Stats recorded 04 Dec 2024 17:25:50

DSLAM/MSAN type:            IFTN:0xb206 / v0xb206
Modem/router firmware:      AnnexA version - A2pv6C038m.d24j
DSL mode:                   VDSL2
Status:                     Showtime
Uptime:                     4 hours 49 min 59 sec
Resyncs:                    0 (since 04 Dec 2024 12:09:17)
            
                Downstream    Upstream
Line attenuation (dB):      13.1        0.0
Signal attenuation (dB):    Not monitored        
Connection speed (kbps):    71131        19996
SNR margin (dB):            6.3        6.0
Power (dBm):                2.1        2.0
Interleave depth:           1        1
INP:                                

RSCorr/RS (%):              0.0000        N/A
RSUnCorr/RS (%):            0.0000        N/A
ES/hour:                    0        0

[#5]

The modem's DSL light stays on and it takes just 10 seconds for the WAN connection to return. Also, there's no sign in the modem's logs of the DSL line going down - or in fact of any event at all. It is noticed only by the router, which returns this error message as the line goes down:

RT-AX58U-A5F2726-C kernel: eth0 (Int switch port: 0) (Logical Port: 0) (phyId: Link DOWN.

I've tried increasing the retries  (PPP Echo Max Failures) but it seems to make little difference. PPP Echo is set to 10.

How would I set 'force link'?

[#6]

How would I set 'force link'?

It's a check box on the Advanced settings tab for the Wan interface. The same page as the LCP echo settings

[#7]

@mdubash  using Luci goto Network->Interfaces, select Edit for the WAN interface, then select the Advanced settings tab. It should look something like this

[#8]

Thanks - I must be going blind because I can see no such option on the WAN settings page. There's no 'Advanced' tab, nor a 'force link' option.

Edit: PS: Just discovered Luci - will investigate. Years of using the simple FritzBox interface have left me out of this loop

[#9]

Just discovered Luci - will investigate

@mdubash did you find the setting ?

TBH I thought Luci was the default gui, I've always used it.

For info, if you need to set the option by editing the config files , its defined here https://openwrt.org/docs/guide-user/network/network_configuration about halfway down the document in the 'Common options' section

[#10]

---

@MisterW wrote:

Just discovered Luci - will investigate

@mdubash did you find the setting ?

TBH I thought Luci was the default gui, I've always used it.

For info, if you need to set the option by editing the config files , its defined here https://openwrt.org/docs/guide-user/network/network_configuration about halfway down the document in the 'Common options' section

---

Thanks - I haven't yet explored this. I think I may have misled everyone: my router firmware is the standard Asus default, not the OpenWRT - couldn't get it to install (whole 'nuther story).

For the moment, and in the interests of time and my need to be getting on with other stuff, I've lengthened the PPP Echo Interval to 30 seconds so I'm hoping for fewer timeouts. I'll return to this asap.

[#11]

---

@Townman wrote:

In the absence of helpful router stats, given that you have seen similar with different kit - consider REIN n SHINE.  See Kitz.

---

Thanks - I've considered it but discounted it: the kit is all in the exact same location as my old FritzBox 7590 which has been rock-solid for the best part of 10 years with no drops at all and top performance.

[I've replaced it because it started making odd whistling noises, a clear sign I reckon of a chip or two starting to EOL.]

[#12]

Thanks - I haven't yet explored this. I think I may have misled everyone: my router firmware is the standard Asus default, not the OpenWRT

Ah! that would explain why your gui is different. Looking at the Openwrt supported Asus hardware https://openwrt.org/toh/asus/start the AX58U isnt there but the AX59U is.

[#13 · Accepted solution]

I've just had a very useful conversation with Tom from Plusnet's tech support. They've validated the back end, there are no line problems reported but they can see the frequent Layer 3 disconnects. Due to my equipment being non-standard (ie not a PN Hub), support was naturally limited but we talked through the potential options, and he eventually suggested swapping the LAN 1 and LAN 2 Ethernet ports, on the grounds that there may be a fault with the (now pretty ancient) modem's LAN 1 port.

If you're unfamiliar with the Huawei HG612 modem, LAN 1 is by default the router connection, while LAN 2 allows access to config and monitoring. So this was definitely worth exploring as an option and is what I've done, essentially bound the WAN connection to LAN 2 and swapped the cables around.

So far, 3 hours later, it's working perfectly. Another 24 hours will tell if that's fixed the problem - or at least provided a suitable workaround...

[#14]

Whilst I've never used one , I am familiar with the HG612.

Swapping the LAN ports certainly is a useful test.

I know you're not using it, but do you actually have a Plusnet Hub 2 ? I ask because the Hub 2 can be set to 'bridge' mode and effectively becomes a modem and so could be used instead of the HG612.

So far, 3 hours later, it's working perfectly. Another 24 hours will tell if that's fixed the problem - or at least provided a suitable workaround...

I didn't realise the drops were quite that frequent, mine were a few days (sometimes up to 10) apart. Since using the force_link my PPPoE has been up for 70 days.

[#15]

my PPPoE has been up for 70 days.

---

@MisterW wrote:

Whilst I've never used one , I am familiar with the HG612.

Swapping the LAN ports certainly is a useful test.

I know you're not using it, but do you actually have a Plusnet Hub 2 ? I ask because the Hub 2 can be set to 'bridge' mode and effectively becomes a modem and so could be used instead of the HG612.

So far, 3 hours later, it's working perfectly. Another 24 hours will tell if that's fixed the problem - or at least provided a suitable workaround...

I didn't realise the drops were quite that frequent, mine were a few days (sometimes up to 10) apart. Since using the force_link my PPPoE has been up for 70 days.

---

My PPoE was the same - with the FritzBox - which sadly doesn't easily succumb to being using purely as a modem which would have been ideal, since the noisy warbling noise mostly abated on disabling the WiFi.

I may have a Hub 2 somewhere, though I've been with PN for over 10 years so it or its predecessor are probably buried in the pile of obsolete tech junk....