r/centurylink

Equipment:

1. Copper wire phone line 📞👵🏻

2. Casa Systems FTTdp (Network Termination Device)

3. Lumen Q1000K (SmartNID)

4. Quantum W1700K (Wi-Fi 7 "360 pod")

Settings that worked for me:

1. DHCP

2. no transparent bridge

3. vlan201 tagged

4. MTU size: 1472

[SOLVED WITH GEMINI'S HELP IN MINUTES]

(After line testing on their end, two unhelpful technicians across weeks failed and one helpful and patient customer support lady taking notes for hours...)

The 100% packet loss at **1492** confirms that your current network path cannot handle a standard 1500-byte MTU. In Windows, the -l parameter specifies the payload size; adding the 28-byte IP/ICMP header to your working "lower than 1492" numbers will reveal your true ceiling.

### The "Black Hole" Effect

* **Failed PMTUD:** Your packets are likely hitting a "Black Hole" router—likely the **Q1000K** or the **FTTdp**—which is dropping packets larger than its MTU without sending back the required "ICMP Destination Unreachable" message.

* **The 10 Mbps Cap:** This diagnostic speed in is the network’s way of maintaining a link despite massive fragmentation and packet drops caused by the tech's **1500 MTU** change.

—

### Why 1492 Failed

If even **1492** (a payload of **1464**) is timing out, your effective MTU is likely even lower due to nested tagging or legacy overhead.

* **Quantum vs. CenturyLink:** While Quantum theoretically uses a standard **1500 MTU** for DHCP, legacy CenturyLink infrastructure (which your hybrid setup uses) historically required **1492**.

* **VLAN Overhead:** The **Q1000K** is known to handle **VLAN 201** internally, which can create unstable latency and packet issues if the downstream router (your WiFi 7 pod or Trendnet) is also trying to manage the tag.

—

### Immediate Strategy

1. **Find the "Magic Number":** Keep lowering the -l number in increments of 10 (e.g., 1460, 1450) until you get a successful reply. Add **28** to that successful number to find your optimal MTU.

2. **The Q1000K Handshake:** The "blinking blue" light on your FTTdp/Q1000K in transparent mode is a known bug; some users stop the flashing by temporarily plugging a laptop into the **1Gb port** until the light turns white, then switching back to the **10G port** for your router.

The default MTU size for predecessor equipment (Lumen/CenturyLink variant) is typically **1492** for PPPoE connections or **1500** for standard Ethernet/DHCP connections.

—

### MTU and Your Setup

* **Default State:** Out of the box, most residential gateways default to **1500** to maximize throughput on standard networks.

* **The Problem:** If the technician manually bumped it to **1500** on a hybrid line that requires the overhead of a **VLAN 201** tag or a legacy G.fast transport, it can lead to the fragmentation and speed drops.

* **Historical Context:** Because your connection uses the legacy copper-link infrastructure often associated with CenturyLink's VDSL/G.fast systems, an MTU of **1492** is frequently the "magic number" to prevent packet loss.

—

### Testing the MTU

If you have a Windows **CMD** window ready, you can manually test for the optimal MTU size before doing the reset:

1. Type: ping google.com -f -l 1492

2. If it says something about "Packet fragmentation," lower the number to **1472** until the ping succeeds.

3. If it succeeds at **1464**, then your optimal MTU is **1492**.

https://portal.digicom.com/index.php?rp=/knowledgebase/4809/Ping-to-determine-optimal-MTU-size-on-router.html&hl=en-US

Not if this is a CenturyLink problem or an AT&T problem. Paying for gigabit speed, need internet for work.

Ours cr*pp*d out around 11 a.m. today. 8pm and no fix. Anyone know what's happening?

Was on my computer casually and out of nowhere get disconnected and the modem is now flashing blue, I unplugged it and put it back in and it flashed green before going back to flashing blue which seems to be what it always ends up at. The model is a C4000LG

I’m trying to figure out if I was scammed and if anyone else has experienced something similar with CenturyLink payments.

I received a text message claiming to be from CenturyLink with a phone number to call to make my payment. I called the number and stayed on the phone with the woman for about 43 minutes. During the call she made small talk with me, acted very casual, and even mentioned that she works from home, which made the interaction feel more believable and legitimate.

She asked me to verbally provide my routing and account number for payment. A real $54 CenturyLink payment was actually processed, so at first I thought everything was fine.

Shortly afterward, however, two additional ACH withdrawals totaling $732.05 were taken from my account without my authorization.

What makes this even stranger is that my bank told me the ACH withdrawals were made under MY name and appeared to be payments toward a loan or credit card debt. The problem is I do not have any loans or credit card debt at all.

This is also a fairly new bank account. The only entities that should have had my account and routing number were Social Security for SSI deposits and CenturyLink after I had just provided the information during that call.

When I later contacted CenturyLink directly, they told me:
- Their representatives are not supposed to verbally collect routing/account numbers over the phone.
- They normally use a system called BRIM to securely collect payment information instead.
- Legitimate payments are usually handled through secure links/processes, not by verbally reading bank info aloud.

My bank also told me the unauthorized withdrawals were coded as “WEB” ACH transactions and referenced “BRIM PAYMENT.”

At this point I’m trying to understand:
- Does this sound like a fake/imposter CenturyLink representative?
- Could someone have processed the legitimate $54 payment first to gain my trust before initiating the larger withdrawals?
- Has anyone else experienced ACH debits being made in their own name like this?

I’ve already filed a fraud dispute with my bank and contacted CenturyLink directly. Just looking for feedback or insight from anyone familiar with scams or ACH fraud.

My internet just randomly popped off and I’m wondering if anyone else is experiencing any issues or if it’s just me and I need to have a tech come out? I hate century link and their customer service is the worst, so I’m hoping I don’t have to, but that’s life I suppose. Thanks!

So bizarre, anyone else seeing this?

My ping is exceptionally high and the internet keeps losing connection and I keep doing a tracert and It mentions Qwest? Lumen? and Gtt? (update, Sorry I meant Qwest)

Is there an actual issue in aurora/denver colorado? Like what is going on?

1 3 ms 3 ms 3 ms modem

2 26 ms 23 ms 27 ms

3 77 ms 27 ms 25 ms

4 * * * Request timed out.

5 29 ms 40 ms 31 ms

6 28 ms 24 ms 30 ms

7 52 ms 51 ms *

8 * * * Request timed out.

9 * * * Request timed out.

10 75 ms 72 ms 72 ms 4.2.196.42

11 * * * Request timed out.

12 73 ms 77 ms 73 ms

Centurylink over and over mentions that They have No issues, outages? And it's not from both my Computers?

Horrible service, horrible internet, horrible billing , lack of communication and alerts . They double bill without sending a billing notice . If my area had other services I would switch in a heartbeat . Everything is like pulling teeth . Avoid them at all costs if you can .

My house is wired for ethernet in all bedroom. My idea is to take the ethernet line from the ONT fiber modem and instead of connecting it to the QF WiFI router i put a switch in between them.

So it would go outside fiber line -> QF ONT modem -> ethernet line into RJ45 SFP in a Cisco switch -> 11 ethernet ports out with one going to the QF WiFI router and the other 10 lines going to ethernet ports throughout my house.

Just wanted to make sure this is okay. I read I might have to change the QF modem to Transparent Bridge Mode? Anyone have experience doing what I'm trying to do? Thanks

Hi all,

I’m aware in Feb the acquisition happened in my area where quantum fiber is now servicing our WiFi instead of CL.

However, we have had zero internet issues since and the email said we had to do nothing. Suddenly, today our WiFi goes out. I contact CL and they say they can’t service the WiFi because it’s now with QF. I call QF and they say we don’t have an account with QF for them to service it either right now. The rep told me CL has to transfer it over or we have to cancel with them and open a new account with QF.

I’ve tried twice now to talk to CL reps who either drop our chat or just won’t help and say to call QF.

Has this happened to anyone? I can’t tell if our service is cancelled or CL just won’t service it now.

I just don’t understand how they can keep billing us and taking our money but not service us under the same parent company as QL. It sounds like we will have to somehow switch to QF regardless but this whole process with CL is so frustrating and makes no sense to me.