Chapter 57. Networking

Verification of signatures using the MD5 hash algorithm is disabled in Red Hat Enterprise Linux 7

It is impossible to connect to any Wi-Fi Protected Access (WPA) Enterprise Access Point (AP) that requires MD5 signed certificates. To work around this problem, copy the wpa_supplicant.service file from the /usr/lib/systemd/system/ directory to the /etc/systemd/system/ directory and add the following line to the Service section of the file:
Environment=OPENSSL_ENABLE_MD5_VERIFY=1
Then run the systemctl daemon-reload command as root to reload the service file.
Important: Note that MD5 certificates are highly insecure and Red Hat does not recommend using them. (BZ#1062656)

Mellanox PMD in DPDK causes a performance drop when IOMMU is enabled inside the guest

When running Mellanox Poll Mode Driver (PMD) in Data Plane Development Kit (DPDK) in the guest, a performance drop is expected if the iommu=pt option is not set.
To make Mellanox PMD work properly, I/O memory management unit (IOMMU) needs to be explicitly enabled in the kernel, and use the passthrough mode. For doing that, pass the intel_iommu=on option (for Intel systems) to the kernel command line. In addition, use iommu=pt to have a proper I/O performance. (BZ#1578688)

freeradius might fail when upgrading from RHEL 7.3

A new configuration property, correct_escapes, in the /etc/raddb/radiusd.conf file was introduced in the freeradius version distributed since RHEL 7.4. When an administrator sets correct_escapes to true, the new regular expression syntax for backslash escaping is expected. If correct_escapes is set to false, the old syntax is expected where backslashes are also escaped. For backward compatibility reasons, false is the default value.
When upgrading, configuration files in the /etc/raddb/ directory are overwritten unless modified by the administrator, so the value of correct_escapes might not always correspond to which type of syntax is used in all the configuration files. As a consequence, authentication with freeradius might fail.
To prevent the problem from occurring, after upgrading from freeradius version 3.0.4 (distributed with RHEL 7.3) and earlier, make sure all configuration files in the /etc/raddb/ directory use the new escaping syntax (no double backslash characters can be found) and that the value of correct_escapes in /etc/raddb/radiusd.conf is set to true.
For more information and examples, see the solution at https://access.redhat.com/solutions/3241961. (BZ#1489758)