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Manual Chapter: General Configuration Properties
Manual Chapter
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TMOS general configuration properties

Part of managing the BIG-IP system involves configuring and maintaining a set of global system properties. These properties allow you to configure:

  • General device features, such as NTP and DNS
  • General local traffic features, including some global persistence settings
  • General global traffic features, including load balancing and metric collection

When you configure general device properties, you are affecting the operation of the BIG-IP system as a whole, rather than just one aspect of it. Similarly, when you configure the general properties related to local traffic or global traffic, you are globally affecting the operation of the local traffic management and global traffic management systems.

About general device properties

The BIG-IP system general device properties that you can view or configure are:

  • The host name
  • The BIG-IP software version number
  • The number of CPUs available
  • The number of CPUs that are active

Other BIG-IP system general device properties that you can configure are:

  • Network boot
  • Quiet boot

You can also perform operations such as reboot or force the system into an OFFLINE state, and reload the default geolocation data files that the BIG-IP system uses to source the origin of a name resolution request.

Note: Regarding the Always-On Management (AOM) subsystem, AOM now saves the recent contents of serial output from the host across host reboots, even when no serial console is attached. The contents are written to log files on both the AOM and the host, either after a host reboot/power event or at a user's request. This feature is disabled by default. To enable the feature, you must open Secure Shell (ssh) and then manually change and restart the hostconsh script. For more information, see the F5 Networks knowledge base at http://support.f5.com.

Updates to the IP geolocation database

The BIG-IP system uses an IP geolocation database to determine the origin of a name resolution request. The default database provides geolocation data for IPv4 addresses at the continent, country, state, ISP, and organization levels. The state-level data is worldwide, and thus includes designations in other countries that correspond to the U.S. state-level in the geolocation hierarchy, for example, provinces in Canada. The default database also provides geolocation data for IPv6 addresses at the continent and country levels.

Note: You can access the ISP and organization-level geolocation data for IPv4 and IPv6 addresses using the iRules whereis command.
Tip: If you require geolocation data at the city-level, contact your F5 Networks sales representative to purchase additional database files.

You can download a monthly update to the IP geolocation database from F5 Networks.

About network time protocol (NTP)

Network Time Protocol (NTP) is a protocol that synchronizes the clocks on a network. Because, by default, DHCP is enabled for the BIG-IP system, on the first boot, the BIG-IP system contacts your DHCP server and obtains the IP address of your NTP server. If the DHCP server provides this IP address, the NTP Device Configuration screen displays the NTP server information. If you do not have a DHCP server on your network, or if the DHCP server does not return the IP address of your NTP server, you can manually add the IP address of the NTP server to the BIG-IP system using the BIG-IP Configuration utility.

About DNS configuration

Domain Name System (DNS) is an industry-standard distributed internet directory service that resolves domain names to IP addresses. When you enable DHCP, the system contacts your DHCP server to obtain the IP addresses of your local DNS servers and the domain names that the system searches to resolve local host names. If the DHCP server provides this information, the DNS Device Configuration screen displays the information in the DNS Lookup Server List and the DNS Search Domain List.

If you do not have a DHCP server on your network, or if the DHCP server does not supply the information, you can manually create the two lists. The DNS Lookup Server List allows BIG-IP system users to use IP addresses, host names, or fully-qualified domain names (FQDNs) to access virtual servers, nodes, or other network objects. The DNS Search Domain List allows BIG-IP system to search for local domain lookups to resolve local host names.

Additionally, you can manually configure the BIND Forwarder Server List that provides DNS resolution for servers and other equipment load balanced by the BIG-IP system, that is, for the servers that the BIG-IP system uses for DNS proxy services.

Note: To use DNS Proxy services, you must enable the named service.

About local-traffic properties

The BIG-IP system includes a set of properties that apply globally to the local traffic management system. These properties fall into two main categories: general local-traffic properties, and persistence properties. You can use the BIG-IP Configuration utility to configure and maintain these properties.

General local traffic properties

This table lists and describes global properties that you can configure to manage the behavior of the local traffic management system.

Property Default Value Description
Auto Last Hop Enabled (checked) Specifies, when checked (enabled), that the system automatically maps the last hop for pools.
Maintenance Mode Disabled (unchecked) Specifies, when checked (enabled), that the unit is in maintenance mode. In maintenance mode, the system stops accepting new connections and slowly completes the processing of existing connections.
VLAN-Keyed Connections Enabled (checked) Check this setting to enable VLAN-keyed connections. VLAN-keyed connections are used when traffic for the same connection must pass through the system several times, on multiple pairs of VLANs (or in different VLAN groups).
Path MTU Discovery Enabled (checked) Specifies, when checked (enabled), that the system discovers the maximum transmission unit (MTU) that it can send over a path without fragmenting TCP packets.
Reject Unmatched Packets Enabled (checked) Specifies that the BIG-IP system sends a TCP RST packet in response to a non-SYN packet that matches a virtual server address and port or self IP address and port, but does not match an established connection. The BIG-IP system also sends a TCP RST packet in response to a packet matching a virtual server address or self IP address but specifying an invalid port. The TCP RST packet is sent on the client-side of the connection, and the source IP address of the reset is the relevant BIG-IP LTM object address or self IP address for which the packet was destined. If you disable this setting, the system silently drops unmatched packets.
Reaper High-water Mark 95 Specifies, in percent, the memory usage at which the system silently purges stale connections, without sending reset packets (RST) to the client. If the memory usage remains above the low-water mark after the purge, then the system starts purging established connections closest to their service timeout. To disable the adaptive reaper, set the high-water mark to 100.
Reaper Low-water Mark 85 Specifies, in percent, the memory usage at which the system starts establishing new connections. Once the system meets the reaper high-water mark, the system does not establish new connections until the memory usage drops below the reaper low-water mark. To disable the adaptive reaper, set the low-water mark to 100. This setting helps to mitigate the effects of a denial-of-service attack.
SYN Check Activation Threshold 16384 Specifies the number of new or untrusted TCP connections that can be established before the system activates the SYN Cookies authentication method for subsequent TCP connections.
Layer 2 Cache Aging Time 300 Specifies, in seconds, the amount of time that records remain in the Layer 2 forwarding table, when the MAC address of the record is no longer detected on the network.
Share Single MAC Address Disabled (unchecked) When this setting is unchecked (disabled), the BIG-IP system assigns to each VLAN a unique MAC address that comes from a pool of available MAC addresses. If you create enough VLANs to exceed the number of MAC addresses available, the system then begins to assign the same MAC address to multiple VLANs. This is the default value and the most common configuration. When this setting is checked (enabled), the BIG-IP system causes all VLANs to share a single MAC address (global). This setting is equivalent to the BigDB variable vlan.macassignment and has two values, unique and global.
SNAT Packet Forwarding TCP and UDP Only Specifies the type of traffic for which the system attempts to forward (instead of reject) Any-IP packets, when the traffic originates from a member of a SNAT. There are two possible values: TCP and UDP Only specifies that the system forwards, for TCP and UDP traffic only, Any-IP packets originating from a SNAT member. All Traffic specifies that the system forwards, for all traffic types, Any-IP packets originating from a SNAT member.
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