Cable break mitigation for stable internet in Vietnam

Another submarine cable incident in Vietnam and your office loses access to Google Drive, GitHub, or the overseas SaaS dashboard you depend on. International routes crawl or drop entirely, yet domestic traffic keeps flowing. This is a recurring pattern with Vietnam internet cable breaks, and it is worth planning around instead of reacting to. The practical play is not to pray for faster repairs, it is to architect so that submarine cable incident Vietnam mitigation barely changes how your team works. This guide lays out the strategies that actually keep stable internet Vietnam for business: local hosting for domestic users, DNS failover, backup WAN links, and caching layers.

Prerequisites

• One Linux VPS running Ubuntu 24.04 LTS or Debian 12, with root or sudo access.
• A domain where you control the DNS records (A, CNAME, MX).
• A second connection or VPS in a different region for failover testing.
• Basic familiarity with SSH and editing config files under /etc.

越南海缆中断时，本地机房和自动切换是保持稳定的关键。

Local hosting and automatic failover are the key to staying stable when Vietnam submarine cables break.

Why submarine cable incidents hit some businesses harder

Vietnam's international traffic rides on a handful of submarine cable systems: AAG, APG, IA, SJC2, and the newer ADC and VCLG. When one breaks, the others absorb the load and latency climbs. A full incident, like the multiple breaks seen in 2023 and 2025, cuts total international capacity by a third or more. Your domestic calls and local website still work because they never leave the country, but any request that crosses the border slows down or times out.

The businesses that suffer least share one trait: they moved the traffic that must stay reliable onto local infrastructure. A Vietnam VPS with a dedicated IPv4 keeps your website, your API, and your customer-facing services inside the domestic network. Vietnamese users reach you over domestic routes that submarine cable incidents do not touch. This is why local hosting is the first mitigation, not the last resort.

What breaks and what keeps working during a submarine cable incident

When an incident happens, the impact is not uniform. Traffic to domestic destinations keeps moving at full speed because it routes through Viettel, VNPT, FPT, and CMC's internal backbones. International traffic splits into two buckets:

• Traffic to Hong Kong, Singapore, and Japan rides the remaining cable systems. It works but latency rises.
• Traffic to the US and Europe degrades most, because fewer redundant paths exist.

The services that vanish first are the ones you do not control: overseas SaaS, public cloud consoles, and CDN origins outside Vietnam. The services that stay up are the ones you host locally. That split defines the entire mitigation strategy: host what you can locally, fail over what you cannot, and cache aggressively in between.

Step 1: Move customer-facing services to a Vietnam VPS

The highest-impact move is hosting your website and application on a Linux VPS inside Vietnam. A user in Hanoi or Ho Chi Minh City then reaches your server through the domestic backbone, which does not depend on submarine cables. The round trip stays under 20 ms instead of jumping to Hong Kong and back.

For a typical web stack, a 2GB RAM VPS is enough. Install Nginx, PHP, and MariaDB, then deploy your application. The key detail is that the datacenter must be on the domestic network with a WordPress-capable VPS or the equivalent, so all local ISPs reach it over their own infrastructure.

# On Ubuntu 24.04, deploy a basic stack
sudo apt update
sudo apt install -y nginx mariadb-server php8.3-fpm php8.3-mysql
sudo systemctl enable --now nginx mariadb php8.3-fpm
sudo systemctl status nginx

Verify nginx is running before you continue. The service must report active, and a request to the server IP must return the default page.

systemctl status nginx
curl -I http://localhost

Step 2: Set up DNS failover so users land on the working path

DNS failover is the second layer. When your primary origin sits overseas and the cable breaks, users cannot reach it. A failover record points them to a local replica or a proxy instead. You can implement this with a short TTL and a monitoring script, or with a managed DNS provider that runs health checks.

The principle is simple: your primary A record points to the overseas server, the backup points to the Vietnam VPS. A script checks reachability every 60 seconds and flips the record when the primary stops responding. Set the TTL to 300 seconds so the flip propagates quickly.

# Health check script skeleton, run every minute via cron
#/usr/local/bin/dns-failover.sh
if ! curl -sf --max-time 10 https://primary.example.com/health; then
    curl -s -X PATCH "https://api.dnsprovider.com/v1/zones/example.com/records" \
        -H "Authorization: Bearer $TOKEN" \
        -d '{"name":"app","type":"A","value":"203.113.x.x","ttl":300}'
    logger "DNS failed over to local VPS"
fi

The same logic applies to any SaaS you depend on. Point a subdomain at the vendor, and if it goes dark during a submarine cable incident, the failover sends you to a cached copy or a maintenance page on local infrastructure. You stay reachable even when the vendor does not.

Step 3: Add a backup WAN link for the office

Office connectivity needs a physical backup. If your primary line is a single ISP, a cable break at the international gateway takes down every overseas session. A second line from a different provider, even a 4G/5G router, gives you a path out when the first fails. The key is that the two providers must not share the same international gateway.

Run the routing this way: domestic traffic uses the primary line, overseas traffic can fail over to the backup. On a Linux router or firewall, policy routing handles this cleanly.

# On a Linux gateway with two uplinks, eth0 primary and eth1 backup
# Default route via primary
ip route add default via 192.168.1.1 dev eth0
# Health check on the primary gateway
while true; do
    if ! ping -c 3 -W 2 8.8.8.8 > /dev/null; then
        ip route replace default via 192.168.2.1 dev eth1
        logger "WAN failed over to backup link"
    fi
    sleep 10
done

This basic script flips the default route when the primary cannot reach the internet. In production use a real failover daemon or a router with Dual-WAN support, but the logic is identical.

Step 4: Cache aggressively with a local proxy or CDN node

Caching shrinks what the cable break can hurt. If your team reads the same documentation, pulls the same Docker images, or syncs the same repositories, a local cache absorbs those requests during an incident. Run a small caching proxy on the Vietnam VPS and point your browsers and package managers at it.

nginx can cache HTTP responses, and a tool like Nexus or Artifactory caches software packages. Even a simple Squid proxy helps for general web traffic. The cache does not eliminate the need for a working international path, but it cuts the volume of traffic that needs one.

# Minimal nginx reverse cache for a remote origin
# /etc/nginx/sites-available/cache
server {
    listen 80;
    location / {
        proxy_pass https://origin.example.com;
        proxy_cache my_cache;
        proxy_cache_valid 200 10m;
    }
}

For software mirrors, point apt or yum at a local mirror that syncs during off-peak hours. When the cable breaks, package installs keep working from the local copy.

Quick reference: what to do when the next incident hits

When you see the news of a Vietnam submarine cable incident, run this checklist instead of panicking:

1. Check whether domestic services are up. They should be, if they run on local infrastructure.
2. Confirm DNS failover fired. Query your domain from an overseas resolver to see which IP answers.
3. Verify the office backup WAN is active. A single ping to a US IP tells you the path state.
4. Watch local caches. If they are absorbing the load, you have time to wait out the repair.

# Verify current path and DNS answer during an incident
dig +short app.example.com
mtr -c 20 -r 1.1.1.1
ss -tlnp | grep :80

FAQ

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• How to choose a reliable Vietnam VPS provider
• Vietnam VPS vs Singapore VPS for serving Vietnamese users