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IPv6 packet sampling
IPv6 sampling is performed by the packet processor. The system uses the sampling rate setting to
selectively mark the monitoring bit in the header of an incoming packet. Marked packets tell the CPU
that the packets are subject to sFlow sampling.
sFlow configuration considerations
This section lists the sFlow configuration considerations on Brocade devices.
On ICX and FCX Series devices, you can use QoS queue 1 for priority traffic, even when sFlow is
enabled on the port. This differs from FastIron X Series devices, which support seven priorities instead
of eight when sFlow is enabled. In this case, QoS queue 1 is reserved for sFlow and is not used by
other packets. Any non-sFlow packets assigned to QoS queue 1 will be directed to QoS queue 0.
If ICX and FCX stacks are rebooted, sFlow is disabled on standby and member units until the
configuration is synchronized between the Active and Standby Controllers.
sFlow and hardware support
• Brocade devices support sFlow packet sampling of inbound traffic only. These devices do not sample
outbound packets. However, Brocade devices support byte and packet count statistics for both traffic
directions.
• sFlow is supported on all Ethernet ports (10/100, Gbps, and 10 Gbps)
sFlow and CPU utilization
Enabling sFlow may cause a slight and noticeable increase of up to 20% in CPU utilization. In typical
scenarios, this is normal behavior for sFlow, and does not affect the functionality of other features on
the switch.
sFlow and agent address
The sampled sFlow data sent to the collectors includes an agent_address field. This field identifies the
IP address of the device that sent the data:
• On a Layer 2 switch, agent_address is the Layer 2 switch management IP address. You must
configure the management IP address in order to export sFlow data from the device. If the switch has
both an IPv4 and IPv6 address, the agent_address is the IPv4 address. If the switch has an IPv6
address only, the agent_address is the global IPv6 address.
• On a Layer 3 switch with IPv6 interfaces only, sFlow looks for an IPv6 address in the following order,
and uses the first address found:
‐
The first IPv6 address on the lowest-numbered loopback interface
‐
The first IPv6 address on the lowest-numbered VE interface
‐
The first IPv6 address on any interface
• On a Layer 3 switch with both IPv4 and IPv6 interfaces, or with IPv4 interfaces only, sFlow looks for
an IP address in the following order, and uses the first address found:
‐
The IPv4 router ID configured by the ip router-id command
‐
The first IPv4 address on the lowest-numbered loopback interface
‐
The first IPv4 address on the lowest-numbered virtual interface
‐
The first IPv4 address on any interface
IPv6 packet sampling
FastIron Ethernet Switch Administration Guide 247
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