Configuration Guide User guide

FastIron Configuration Guide 537
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sFlow
Extended gateway information
If BGP is enabled, extended gateway information is included in IPv6 sFlow sampled packets,
including the following BGP information about a packet destination route:
• The autonomous system (AS) number for the router
• The source IP AS of the route
• The source peer AS for the route
• The AS patch to the destination
NOTE
AS communities and local preferences are not included in the sampled packets.
To obtain extended gateway information, use “struct extended_gateway” as described in RFC 3176.
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 FWS 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 an FCX stack is 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 source 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: