IP Tunable Parameters

_icmp_err_interval and _icmp_err_burst

Description

Controls the rate of IP in generating ICMP error messages. IP generates only up to _icmp_err_burst IP error messages in any _icmp_err_interval.

The _icmp_err_interval parameter protects IP from denial of service attacks. Setting this parameter to 0 disables rate limiting. It does not disable the generation of error messages.

Default

100 milliseconds for _icmp_err_interval

10 error messages for _icmp_err_burst

Range

0 – 99,999 milliseconds for _icmp_err_interval

1 – 99,999 error messages for _icmp_err_burst

Dynamic?

Yes

When to Change

If you need a higher error message generation rate for diagnostic purposes.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

_respond_to_echo_broadcast and _respond_to_echo_multicast (ipv4 or ipv6)

Description

Controls whether IP responds to a broadcast ICMPv4 echo request or a IPv6 multicast ICMPv6 echo request.

Default

1 (enabled)

Range

0 (disabled) or 1 (enabled)

Dynamic?

Yes

When to Change

If you do not want this behavior for security reasons, disable it.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

_send_redirects (ipv4 or ipv6)

Description

Controls whether IPv4 or IPv6 sends out ICMPv4 or ICMPv6 redirect messages.

Default

1 (enabled)

Range

0 (disabled) or 1 (enabled)

Dynamic?

Yes

When to Change

If you do not want this behavior for security reasons, disable it.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

forwarding (ipv4 or ipv6)

Description

Controls whether IPv4 or IPv6 forwards packets with source IPv4 routing options or IPv6 routing headers.

Default

0 (disabled or off)

Range

0 (disabled or off) or 1 (enabled or on)

Dynamic?

Yes

When to Change

Keep this parameter disabled to prevent denial of service attacks.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

ttl

Description

Controls the time to live (TTL) value in the IPv4 header for the outbound IPv4 packets on an IP association.

Default

255

Range

1 to 255

Dynamic?

Yes

When to Change

Generally, you do not need to change this value.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

hoplimit (ipv6)

Description

Sets the value of the hop limit in the IPv6 header for the outbound IPv6 packets on an IP association.

Default

255

Range

0 to 255

Dynamic?

Yes

When to Change

Generally, you do not need to change this value.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

_addrs_per_if

Description

Defines the maximum number of logical IP interfaces associated with a real interface.

Default

256

Range

1 to 8,192

Dynamic?

Yes

When to Change

Do not change the value. If more logical interfaces are required, you might consider increasing the value. However, recognize that this change might have a negative impact on IP's performance.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

hostmodel (ipv4 or ipv6)

Description

Controls send and receive behavior for IPv4 or IPv6 packets on a multi-homed system. This property can have the following values: weak, strong, and src-priority. The default value is weak.

Default

weak

Range

weak, strong, or src-priority

• weak

  • Outgoing packets - The source address of the packet going out need not match the address configured on the outgoing interface.

  • Incoming packets - The destination address of the incoming packet need not match the address configured on the incoming interface.

  • strong

    • Outgoing packets - The source address of the packet going out must match the address configured on the outgoing interface.

    • Incoming packets - The destination address of the incoming packet must match the address configured on the incoming interface.

  • src-priority

    • Outgoing packets - If multiple routes for the IP destination in the packet are available, the system prefers routes where the IP source address in the packet is configured on the outgoing interface.

      If no such route is available, the system falls back to selecting the best route, as with the weak ES case.

    • Incoming packets - The destination address of the incoming packet must be configured on any one of the host's interface.

Dynamic?

Yes

When to Change

If a machine has interfaces that cross strict networking domains (for example, a firewall or a VPN node), set this parameter to strong.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

ip_squeue_fanout

Description

Determines the mode of associating TCP/IP connections with squeues.

A value of 0 associates a new TCP/IP connection with the CPU that creates the connection. A value of 1 associates the connection with multiple squeues that belong to different CPUs.

Default

1

Range

0 or 1

Dynamic?

Yes

When to Change

Consider setting this parameter to 1 to spread the load across all CPUs in certain situations. For example, when the number of CPUs exceed the number of NICs, and one CPU is not capable of handling the network load of a single NIC, change this parameter to 1.

This property can only be set in the /etc/system file.

Zone Configuration

This parameter can only be set in the global zone.

Commitment Level

Unstable

IP Tunable Parameters With Additional Cautions

Changing the following parameters is not recommended.

_pathmtu_interval

Description

Specifies the interval in milliseconds when IP flushes the path maximum transfer unit (PMTU) discovery information, and tries to rediscover PMTU.

Refer to RFC 1191 on PMTU discovery.

Default

1200 milliseconds (20 minutes)

Range

2-999999999

Dynamic?

Yes

When to Change

Do not change this value.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).

_icmp_return_data_bytes (ipv4 or ipv6)

Description

When IPv4 or IPv6 sends an ICMPv4 or ICMPv6 error message, it includes the IP header of the packet that caused the error message. This parameter controls how many extra bytes of the packet beyond the IPv4 or IPv6 header are included in the ICMPv4 or ICMPv6 error message.

Default

64 for IPv4

1280 for IPv6

Range

8-6,636 for IPv4

8-1,280 for IPv6

Dynamic?

Yes

When to Change

Do not change the value. Including more information in an ICMP error message might help in diagnosing network problems. If this feature is needed, increase the value.

Commitment Level

Unstable

Change History

For information, see IP Parameter Name Changes (Oracle Solaris 11).