Blocked ports and internet resources

Last update: October 05 2026Open in Markdown

A number of TCP/UDP ports are blocked in the Selectel infrastructure; details and a list of such ports are in the Blocked ports subsection.

Also, access to public subnets of the e-government is blocked from the Selectel infrastructure. For example, the Gosuslugi portal and related services are located in such a subnet.

You can view the full list of internet resources that belong to the e-government in the What is e-government instructions in the Gosuslugi portal documentation.

You can submit an unblock request. We consider each request individually, but cannot guarantee unblocking.

Blocked ports

To secure the Selectel infrastructure from malicious network activity, we limit access to certain TCP/UDP ports. Incoming and outgoing traffic is blocked as it passes through the border routers at the edge of the Selectel network.

For TCP ports 25, 465, and 587, only outgoing traffic to public IPv4 and IPv6 addresses is blocked. Instead of these ports, we recommend using the Selectel email service.

The full list of blocked ports is specified in the List of blocked ports table. If a port is unavailable, but is not listed in the table, check its availability from the operating system side using the nmap utility.

List of blocked ports

Port and application protocol	Port purpose	Transport protocol	Reason for blocking	Requesting unblocking is possible
17 QOTD	Transmission of a short text message when a client connects to a server	TCP/UDP	low security level; risk of amplification attacks	✗
25 SMTP	Sending emails between servers in plaintext	TCP	spam prevention; risk of interception of unencrypted traffic	✓
111 ONC RPC (SunRPC)	Mapping RPC services (nfs, mountd, etc.) to port numbers on the server	TCP/UDP	risk of discovering all RPC services; risk of unauthorized file access	✗
135 Microsoft EPMAP	Mapping RPC calls to specific services and ports on a remote system	TCP/UDP	risk of unauthorized system access; risk of interception and manipulation of RPC calls (MITM); risk of service or method enumeration	✓
137 NetBIOS Name Service	Resolving computer names in a local network using the NetBIOS protocol	TCP/UDP	risk of network reconnaissance; risk of unauthorized access to resources; device name spoofing in the network; risk of DoS attacks through broadcast traffic overload	✓
138 NetBIOS Datagram Service	Transferring small messages between devices in a network without establishing a connection	TCP/UDP	risk of attacks via unencrypted data transmission; risk of DoS attacks through broadcast traffic overload; risk of gathering information about hosts, users, and shared resources	✓
139 NetBIOS Session Service	Shared access to files, printers, and ports in Windows networks via NetBIOS	TCP/UDP	risk of attacks on SMB and NetBIOS vulnerabilities; risk of network scanning and information gathering	✓
389 LDAP	Connecting to an LDAP directory for authentication and data search	TCP/UDP	risk of password brute-forcing; risk of unauthorized access to directory data	✗
427 SLP	Discovering network services and devices in a local network	TCP/UDP	risk of amplification attacks; risk of internal network structure exposure	✗
445 SMB	File sharing in Windows networks via TCP/IP without NetBIOS	TCP/UDP	risk of attacks on SMB vulnerabilities; risk of password brute-forcing; risk of malware propagation	✓
465 SMTPS	Secure email sending (SMTPS) using SSL/TLS encryption	TCP	risk of downgrade attacks; risk of hiding malicious traffic from analysis	✓
520 RIP	Exchanging routing information in small networks using the RIP protocol	UDP	risk of traffic redirection for data interception (route spoofing); risk of traffic redirection to a malicious node (MITM); risk of DoS attacks via malicious updates	✗
587 SMTP	Secure email sending via SMTP using STARTTLS	TCP	risk of spam and phishing due to weak security; risk of password brute-forcing; risk of data leakage with disabled or weak encryption	✓
1900 SSDP	Device and service discovery in a local network (printers, TVs, routers)	UDP	risk of DoS attacks through request overload; risk of automatic port opening on a router	✗
3702 WS-Discovery	Dynamic web service discovery in a local network	UDP	risk of amplification attacks; risk of unauthorized access to devices	✗
11211 Memcached	Access to Memcached cache server for accelerating web applications	TCP/UDP	risk of amplification attacks; risk of data leakage in the absence of authentication	✗

Submit a request for unblocking

You can submit a request for unblocking:

• access to e-government subnets;

• mail ports 25, 465, 587;

• ports 135, 137, 138, 139, 445.

Each request is reviewed individually, but we cannot guarantee that access will be unblocked and reserve the right to refuse without explanation.

After unblocking, the port or access to the subnet may be blocked again, for example, if spam is sent or your IP address is blacklisted. For more information, see the Network blocks instructions.

Access to e-government subnets

You cannot unblock access to e-government subnets for VDS servers.

Each unblocking request is reviewed individually, but we cannot guarantee that the port will be unblocked and reserve the right to decline requests without providing a reason.

Dedicated Servers

1. Create a ticket. In the ticket, specify:

   • the purpose of access;

   • IP addresses or subnets from which traffic will originate.

2. Wait for a response from a Selectel employee in the ticket regarding the decision.

Cloud servers

You can submit a port unblock request only for a cloud server public subnet.

1. Make sure the server IP address belongs to a public subnet. In the control panel, in the top menu, click Products → Cloud Servers → the Network section → the Public Subnets tab → view the list of networks. If the IP address does not belong to a public subnet, the port cannot be unblocked for it.

2. Create a ticket. In the ticket, specify:

   • the purpose of access;

   • IP addresses or subnets from which traffic will originate.

3. Wait for a response from a Selectel employee in the ticket regarding the decision.

Ports 25, 465, 587

We consider each unblock request individually, but cannot guarantee unblocking, and also reserve the right to refuse without explanation. Instead of ports 25, 465, and 587, we recommend using the Selectel email service.

If we approve your request, ports 25, 465, and 587 will be unblocked for all public addresses in the account, except for:

• IP addresses of dedicated servers in the pools TAS-1, TAS-2, ALM-1, NBO-1;
• IP addresses of the Cloud Platform in the pools uz-1, uz-2, kz-1, ke-1, as well as direct public IP addresses in all pools ;
• IP addresses of VDS servers.

To request unblocking of email ports:

1. Create a ticket. In the ticket, specify:

   • types of emails — for example, transactional, business correspondence, newsletters, etc.;
   • examples of emails;
   • planned subjects (email topics);
   • the domain from which the emails will be sent;
   • expected sending volume — number of emails per week.

2. Wait for a response from a Selectel employee in the ticket regarding the decision.

Ports 135, 137, 138, 139, 445

You cannot unblock ports 135, 137, 138, 139, and 445 for VDS servers.

Ports 135, 137, 138, 139, and 445 can only be unblocked for servers in Russia. This cannot be done for servers in other countries.

We review every unblocking request on a case-by-case basis, but we cannot guarantee that ports will be unblocked and reserve the right to refuse without providing reasons.

Dedicated Servers

You can submit a port unblock request only for a dedicated server public dedicated subnet.

1. Make sure the server IP address belongs to a public dedicated subnet. In the control panel, in the top menu, click Products → Dedicated Servers → Network → the Public Subnets tab → select the subnet type Dedicated → view the list of networks. If the IP address does not belong to a public dedicated subnet, the port cannot be unblocked for it.

2. Create a ticket. In the ticket, specify:

   • the port to be unblocked;
   • the purpose of using the port;
   • the public dedicated subnet of the dedicated server for which you need to unblock the port. You can view the list of public dedicated subnets in the control panel: in the top menu, click Products → Dedicated Servers → Network → the Public Subnets tab → select the subnet type Dedicated.

3. Wait for a response from a Selectel employee in the ticket regarding the decision.

Cloud servers

You can submit a port unblock request only for a cloud server public subnet.

1. Make sure the server IP address belongs to a public subnet. In the control panel, in the top menu, click Products → Cloud Servers → the Network section → the Public Subnets tab → view the list of networks. If the IP address does not belong to a public subnet, the port cannot be unblocked for it.

2. Create a ticket. In the ticket, specify:

   • the port to be unblocked;
   • the purpose of using the port;
   • the cloud server public subnet for which you need to unblock the port. You can view the list of public subnets in the control panel: in the top menu, click Products → Cloud Servers → the Network section → the Public Subnets tab.

3. Wait for a response from a Selectel employee in the ticket regarding the decision.