Limitations and usage guidelines

The following are the limitations and some usage guidelines related to NetScaler BLX appliances.

• When you set the hostname of the NetScaler BLX appliance using the set ns hostname command, the hostname of the Linux host is also changed.
• The following are the limitations related to LA/LACP channels:
  • LA/LACP channels aren’t supported for shared mode NIC interfaces.
  • LA/LACP channels are supported only between dedicated NIC interfaces or only between DPDK NIC interfaces.
  • LA/LACP channels aren’t supported for blx1 and ns1 virtual interfaces.

• High availability is supported for BLX appliances only in dedicated mode.

• High availability for BLX appliances isn’t supported if the nsinternal user login is disabled.

• In a high availability setup of NetScaler BLX enabled with host mode, host access is lost when you add or remove an HA node until the new configurations are applied. To restore the connection, you must retry connecting to the host.

• Web application firewall (WAF) is supported only for BLX in dedicated mode.

• In a BLX appliance deployed in dedicated mode, management HTTP or HTTPS port (mgmt-http-port or mgmt-https-port) settings specified in the BLX configuration file do not apply. By default, 9080 and 9443 port numbers are dedicated for HTTP and HTTPS management access.

  To change these ports for BLX appliances in dedicated mode, you must use the Citrix ADC command:

  set ns param (-mgmthttpport <value> | -mgmthttpsport <value>).

  Example:

  set ns param -mgmthttpport 2080"

• If the firewall is enabled on the Linux host, then you might have to add exceptions for the BLX management ports in addition to the SYSLOG ports.

• A stable start for a BLX appliance might take around 45 seconds.

• BLX configurations are stored in the /nsconfig/ns.conf file. For configurations to be available across sessions, you must save the configuration after every configuration change.

  To view the running configuration by using the BLX CLI

  At the BLX CLI prompt, type:

  show ns runningConfig

  To save configurations by using the BLX CLI

  At the command prompt, type:

  save ns config

• The BLX configurations in /nsconfig/ns.conf take precedence over /etc/blx/blx.conf file.

• A BLX appliance does not start if the memory allocated is less than 1 GB per BLX worker-processes.

• The following system settings are changed on installing a BLX appliance in a Linux environment: ip_forward is set to 1.

• After a BLX appliance is uninstalled, BLX configuration file blx.conf is retained and backed up as blx.conf.rpmsave.

  To apply this backup configuration file to a newly installed BLX appliance on the same Linux host, you must manually rename the file back to blx.conf

• Citrix does not recommend running a BLX appliance on the following Ubuntu version because the BLX appliance might run into some packet drop related issues.

  Ubuntu version 16.04.5 with kernel version 4.4.0-131-generic

• A BLX appliance deployed on CentOS Linux version 8.0 host or Oracle Linux version 8.0 host might not start or function properly if the following condition is met:

  • SELinux policy is enabled on the Linux host. SELinux prevents the systemd process from running some BLX system files.

  Workaround: Disable SELinux on the Linux host.

• A BLX appliance supports a maximum of nine NIC ports (DPDK NIC ports, or non-DPDK NIC ports, or both).

Limitations specific to a BLX appliance with DPDK support

• A BLX appliance with DPDK support might fail to start on Linux hosts running on some older CPU models.

  Examples:

  • Intel(R) Xeon(R) CPU E5-2690 v4 @ 2.60 GHz

  • Intel(R) Xeon(R) CPU E5504 @ 2.00 GHz

• The Linux host might crash if you unbind NICs bound to the DPDK module when the BLX appliance is running.

• A BLX appliance with DPDK support takes a little more time to restart as compared to a BLX appliance without DPDK support.

• DPDK configurations (DPDK IGB UIO insertion, DPDK bound ports, and huge pages) on the Linux host are lost whenever the host is restarted. Because of this reason, the BLX appliance will fail to start after the Linux host is restarted. You must reconfigure DPDK for the BLX appliance on the Linux host every time the host is restarted.

  For more information on configuring DPDK on the Linux host, see Configure DPDK on the Linux host.

• All DPDK bound Linux NIC ports are automatically dedicated for the BLX appliance and can’t be used for other DPDK Linux applications.

Limitations of Mellanox NICs in a BLX appliance with DPDK support

• A BLX appliance supports only one type of DPDK NICs at a time. For example, either all Mellanox NICs or all Intel NICs.

• A BLX appliance supports only the MLX5 DPDK driver for Mellanox NICs.

• For more information about the MLX5 DPDK driver and its limitations, see the official MLX5 DPDK documentation.

• For more information about Mellanox NICs and its limitations, see the official Mellanox documentation.