Remote Network Monitoring
December 2005 © Foundry Networks, Inc. B - 11
Extended Router Information
Extended router information contains information for the next hop router. This information includes the next hop
router’s IP address and the outgoing VLAN ID. Extended router information also includes the source IP address
prefix length and the destination IP address prefix length.
Note that in IPv4, prefix length of source and destination IP addresses is collected only if BGP is configured on the
devices. In IPv6, the information is collected if BGP is configured and once the route lookup is complete.
To obtain extended router information in IPv6 sampled packets, use “struct extended_router” as presented in RFC
3176.
Extended Gateway Information
Extended gateway information is included in an sFlow sampled packet if BGP is enabled. The extended gateway
information includes the following BGP information about the packet’s destination route:
• This router’s autonomous system (AS) number
• The route’s source IP AS
• The route’s source peer AS
• The AS path 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.
Configuring and Enabling sFlow
To configure sFlow:
• Specify collector information. The collector is the external device to which you are exporting the sFlow data.
You can specify up to four collectors.
• Optional – Change the polling interval.
• Optional – Change the sampling rate.
• Enable sFlow globally.
• Enable sFlow forwarding on individual interfaces.
NOTE: If you change the router ID or other IP address value that sFlow uses for its agent_address, you need to
disable and then re-enable sFlow to cause the feature to use the new source address.
Specifying the Collector
sFlow exports traffic statistics to an external collector. You can specify up to four collectors. You can specify more
than one collector with the same IP address if the UDP port numbers are unique. You can have up to four unique
combinations of IP address and UDP port number.
To specify sFlow collectors, enter a command such as the following:
FESX424 Router(config)# sflow destination 10.10.10.1
This command specifies a collector with IP address 10.10.10.1, listening for sFlow data on UDP port 6343.
Syntax: [no] sflow destination <ip-addr> [<dest-udp-port>]
The <ip-addr> parameter specifies the collector’s IP address.
The <dest-udp-port> parameter specifies the UDP port on which the sFlow collector will be listening for exported
sFlow data. The default port number is 6343.
The sampled sFlow data sent to the collectors includes an agent_address field. This field identifies the device that
sent the data. See “Source Address” on page B-10.
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