This page sets out the MTU settings and port restrictions that apply to Virtual Server instances.
MTU
With 20–100 bytes of tunnel overhead, 1400 avoids fragmentation along the path and keeps performance steady when AnyCast paths change.
| MTU | Setting | Fragmentation | Note |
|---|---|---|---|
| 1400 | Recommended | None | Best throughput and stability |
| 1476 | Allowed | Low | Usually fine |
| 1500 | Standard | Possible | May slow down on some paths |
Ports blocked by default, can be unblocked
Send port requests through a Portal ticket or support@packet.stream.
| Port | Protocol | Service | Condition |
|---|---|---|---|
| 25 | TCP | SMTP | Unblocked after you explain the sending purpose |
| 137–139 | TCP/UDP | NetBIOS | Business file sharing |
| 445 | TCP/UDP | SMB | Business file sharing |
| 1688 | TCP/UDP | Windows KMS | License management |
Ports always blocked
| Port | Protocol | Service | Reason |
|---|---|---|---|
| 17 | TCP/UDP | QOTD | DDoS amplification |
| 19 | TCP/UDP | Chargen | DDoS amplification |
| 1900 | TCP/UDP | SSDP | UPnP abuse |
| 11211 | UDP | Memcached | DDoS amplification |
| 53413 | UDP | Netis backdoor | Known vulnerability |