samsung usb tether notes

README.md

AT&T US Prepaid + Samsung A71 USB Tethering Fix

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I. Samsung A71: APN Configuration

1. Path: Settings > Connections > Mobile Networks > Access Point Names.

2. Edit: Select active APN (NXTGENPHONE / ENHANCEDPHONE).

3. Update APN Type: Append ,dun,hipri to existing string.

   • Target: default,mms,supl,fota,dun,hipri

4. Protocol: Ensure APN Protocol and APN Roaming Protocol are set to IPv4/IPv6.

5. Commit: Three Dots > Save > Toggle Airplane Mode ON/OFF.

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II. Ubuntu 25.10: Terminal Commands

1. Change TTL (Mask PC traffic as Phone traffic)

Bash

/* Temporary Test */
sudo sysctl -w net.ipv4.ip_default_ttl=65

/* Permanent Apply */
echo "net.ipv4.ip_default_ttl=65" | sudo tee -a /etc/sysctl.conf && sudo sysctl -p

2. Network & DNS Reset

Bash

/* Flush DNS cache */
sudo resolvectl flush-caches

/* Restart Network Manager */
sudo systemctl restart NetworkManager

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III. Ubuntu 25.10: DNS & UI Fix

1. Static DNS (Bypass AT&T Redirects)

• Settings > Network > Wired (USB) or Wi-Fi > Gear Icon.

• IPv4 Tab: Set DNS to Manual.

• Value: 1.1.1.1, 8.8.8.8

• Apply > Toggle Connection OFF/ON.

2. Remove '?' (Disable Connectivity Check)

Bash

sudo sed -i 's/enabled=true/enabled=false/' /etc/NetworkManager/conf.d/20-connectivity.conf
sudo systemctl restart NetworkManager

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**IV. Testing Connection **

Bash

/* Test Raw IP Routing */
ping -c 3 8.8.8.8

/* Test DNS Resolution */
ping -c 3 google.com