End-of-Life (EoL)

Session Settings

The following table describes session settings.
Session Settings
Rematch Sessions
and select
Rematch Sessions
to cause the firewall to apply newly configured security policies to sessions that are already in progress. This capability is enabled by default. If this setting is disabled, any policy change applies only to sessions initiated after the policy change was committed.
For example, if a Telnet session started while an associated policy was configured that allowed Telnet, and you subsequently committed a policy change to deny Telnet, the firewall applies the revised policy to the current session and blocks it.
Rematch Sessions
to apply your latest Security policy to currently active sessions.
ICMPv6 Token Bucket Size
Enter the bucket size for rate limiting of ICMPv6 error messages. The token bucket size is a parameter of the token bucket algorithm that controls how bursty the ICMPv6 error packets can be (range is 10–65,535 packets; default 100).
ICMPv6 Error Packet Rate
Enter the average number of ICMPv6 error packets per second allowed globally through the firewall (range is 10–65,535 packets/second; default is 100 packets/second). This value applies to all interfaces. If the firewall reaches the ICMPv6 error packet rate, the ICMPv6 token bucket is used to enable throttling of ICMPv6 error messages.
Enable IPv6 Firewalling
To enable firewall capabilities for IPv6, click
and select
IPv6 Firewalling
All IPv6-based configurations are ignored if IPv6 is not enabled. Even if IPv6 is enabled for an interface, the
IPv6 Firewalling
option must also be enabled for IPv6 to function.
Enable Jumbo Frame
Global MTU
Select to enable jumbo frame support on Ethernet interfaces. Jumbo frames have a maximum transmission unit (MTU) of 9192 bytes and are available on certain models.
  • If you do not check
    Enable Jumbo Frame
    , the
    Global MTU
    defaults to 1500 bytes (range is 576–1,500).
  • If you check
    Enable Jumbo Frame
    , the
    Global MTU
    defaults to 9,192 bytes (range is 9,192–9,216 bytes).
    Jumbo Frames can take up to five times more memory compared to normal packets and can reduce the number of available packet-buffers by 20%. This reduces the queue sizes dedicated for out of order, application identification, and other such packet processing tasks. As of PAN-OS 8.1, if you enable the jumbo frame global MTU configuration and reboot your firewall, packet buffers are then redistributed to process jumbo frames more efficiently.
If you enable jumbo frames and you have interfaces where the MTU is not specifically configured, those interfaces will automatically inherit the jumbo frame size. Therefore, before you enable jumbo frames, if you have any interface that you do not want to have jumbo frames, you must set the MTU for that interface to 1500 bytes or another value. To configure the MTU for the interface (
), see PA-7000 Series Layer 3 Interface.
NAT64 IPv6 Minimum Network MTU
Enter the global MTU for IPv6 translated traffic. The default of 1,280 bytes is based on the standard minimum MTU for IPv6 traffic. Range is 1,280-9,216.
NAT Oversubscription Rate
Select the DIPP NAT oversubscription rate, which is the number of times that the same translated IP address and port pair can be used concurrently. Reducing the oversubscription rate will decrease the number of source device translations, but will provide higher NAT rule capacities.
  • Platform Default
    —Explicit configuration of the oversubscription rate is turned off; the default oversubscription rate for the model applies. See default rates of firewall models at https://www.paloaltonetworks.com/products/product-selection.html.
  • 1x
    —1 time. This means no oversubscription; each translated IP address and port pair can be used only once at a time.
  • 2x
    —2 times
  • 4x
    —4 times
  • 8x
    —8 times
ICMP Unreachable Packet Rate (per sec)
Define the maximum number of ICMP Unreachable responses that the firewall can send per second. This limit is shared by IPv4 and IPv6 packets.
Default value is 200 messages per second (range is 1–65,535).
Accelerated Aging
Enables accelerated aging-out of idle sessions.
Select this option to enable accelerated aging and specify the threshold (%) and scaling factor.
When the session table reaches the
Accelerated Aging Threshold
(% full), PAN-OS applies the
Accelerated Aging Scaling Factor
to the aging calculations for all sessions. The default scaling factor is 2, meaning that accelerated aging occurs at a rate twice as fast as the configured idle time. The configured idle time divided by 2 results in a faster timeout of one-half the time. To calculate the session’s accelerated aging, PAN-OS divides the configured idle time (for that type of session) by the scaling factor to determine a shorter timeout.
For example, if the scaling factor is 10, a session that would normally time out after 3600 seconds would time out 10 times faster (in 1/10 of the time), which is 360 seconds.
Enable an accelerated aging threshold and set an acceptable scaling factor to free up session table space faster when the session table begins to fill up.
Packet Buffer Protection
As a best practice, enable packet buffer protection globally and on each zone to protect the firewall buffers from DoS attacks and aggressive sessions and sources. This option protects the receive buffers on the firewall from attacks or abusive traffic that causes system resources to back up and legitimate traffic to be dropped. Packet buffer protection identifies offending sessions, uses Random Early Detection (RED) as a first line of defense, and discards the session or blocks the offending IP address if abuse continues. If the firewall detects many small sessions or rapid session creation (or both) from a particular IP address, it blocks that IP address.
Take baseline measurements of firewall packet buffer utilization to understand the firewall capacity and ensure that the firewall is properly sized so that only an attack causes a large spike in buffer usage.
  • Alert (%)
    —When packet buffer utilization exceeds this threshold for more than 10 seconds, the firewall creates a log event every minute. The firewall generates log events when packet buffer protection is enabled globally (range is 0% to 99%; default is 50%). If the value is 0%, the firewall does not create a log event. Start with the default threshold value and adjust as necessary.
  • Activate (%)
    —When this threshold is reached, the firewall begins to mitigate the most abusive sessions (range is 0% to 99%; default is 50%). If the value is 0%, the firewall does not apply RED. Start with the default threshold value and adjust as necessary.
  • Block Hold Time (sec)
    —The amount of time, in seconds, the session is allowed to continue before the session is discarded or the source IP address is blocked (range is 0 to 65,535; default is 60). This timer monitors RED-mitigated sessions to see if they are still pushing buffer utilization above the configured threshold. If the abusive behavior continues past the block hold time, the session is discarded. If the value is 0, the firewall does not discard sessions based on packet buffer protection. Start with the default value, monitor packet buffer utilization, and adjust the time value as necessary.
  • Block Duration (sec)
    —The amount of time, in seconds, that a discarded session remains discarded or a blocked IP address remains blocked (range is 1 to 15,999,999; default is 3,600). Use the default value unless blocking an IP address for one hour is too severe a penalty for your business conditions, in which case you can reduce the duration. Monitor packet buffer utilization and adjust the duration as necessary.
Network Address Translation can increase packet buffer utilization. If this affects the buffer utilization, reduce the Block Hold Time to block individual sessions faster and reduce the Block Duration so other sessions from the underlying IP address aren’t unduly penalized.
Multicast Route Setup Buffering
Select this option (disabled by default) to enable multicast route setup buffering, which allows the firewall to preserve the first packet in a multicast session when the multicast route or forwarding information base (FIB) entry does not yet exist for the corresponding multicast group. By default, the firewall does not buffer the first multicast packet in a new session; instead, it uses the first packet to set up the multicast route. This is expected behavior for multicast traffic. You only need to enable multicast route setup buffering if your content servers are directly connected to the firewall and your custom application cannot withstand the first packet in the session being dropped.
Multicast Route Setup Buffer Size
If you enable Multicast Route Setup Buffering, you can tune the buffer size, which specifies the buffer size per flow (range is 1 to 2,000; default is 1,000.) The firewall can buffer a maximum of 5,000 packets.

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