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Chapter 6. Ports required for communication between IdM and AD

To enable communication between your Active Directory (AD) and Identity Management (IdM) environments, open the following ports on the firewalls of your AD Domain Controllers and IdM servers.

Table 6.1. Ports required for an AD trust

ServicePortProtocol

Endpoint resolution portmapper

135

TCP

NetBIOS-DGM

138

TCP and UDP

NetBIOS-SSN

139

TCP and UDP

Microsoft-DS

445

TCP and UDP

Dynamic RPC

49152-65535

TCP

AD Global Catalog

3268

TCP

LDAP

389

TCP and UDP

Note

The TCP port 389 is not required to be open on IdM servers for trust, but it is necessary for clients communicating with the IdM server.

To open ports, you can use the following methods:

  • Firewalld service — you can enable the particular ports or enable the following services which includes the ports:

    • FreeIPA trust setup
    • FreeIPA with LDAP
    • Kerberos
    • DNS

    For details, see Controlling ports using CLI.

Note

If you are using RHEL 8.2 and earlier, the freeipa-trust Firewalld service includes an RPC port range of 1024-1300, which is incorrect. On RHEL 8.2 and earlier, you must manually open the TCP port range 49152-65535 in addition to enabling the freeipa-trust Firewalld service.

This issue has been fixed for RHEL 8.3 and later in Bug 1850418 - update freeipa-trust.xml definition to include correct dynamic RPC range.

Table 6.2. Ports required by IdM servers in a trust

ServicePortProtocol

Kerberos

88, 464

TCP and UDP

LDAP

389

TCP

DNS

53

TCP and UDP

Table 6.3. Ports required by IdM clients in an AD trust

ServicePortProtocol

Kerberos

88

UDP and TCP

Note

The libkrb5 library uses UDP and falls back to the TCP protocol if the data sent from the Key Distribution Centre (KDC) is too large. Active Directory attaches a Privilege Attribute Certificate (PAC) to the Kerberos ticket, which increases the size and requires to use the TCP protocol. To avoid the fall-back and resending the request, by default, SSSD in Red Hat Enterprise Linux 7.4 and later uses TCP for user authentication. If you want to configure the size before libkrb5 uses TCP, set the udp_preference_limit in the /etc/krb.5.conf file. For details, see the krb5.conf(5) man page.

The following diagram shows the ports and protocols that IdM clients, IdM servers, and AD Domain Controllers use when communicating with each other.

diagram showing the ports and protocols that IdM clients use when communicating with IdM servers and AD Domain Controllers

Additional resources