User`s manual

394
DWS-1008 User’s Manual
D-Link Systems, Inc.
Appendix A - Troubleshooting
• If the snoop lter is running on a Distributed AP, and the AP used a DHCP server in
its local subnet to congure its IP information, and the AP did not receive a default
gateway address as a result, the observer must also be in the same subnet. Without
a default gateway, the AP cannot nd the observer.
• The AP that is running a snoop lter forwards snooped packets directly to the
observer. This is a one-way communication, from the AP to the observer. If the
observer is not present, the AP still sends the snoop packets, which use bandwidth. If
the observer is present but is not listening to TZSP trafc, the observer continuously
sends ICMP error indications back to the AP. These ICMP messages can affect
network and AP performance.
To inform you of this condition, MSS generates a log message such as the following the rst
time an ICMP error message is received following the start of a snoop lter:
AP Mar 25 13:15:21.681369 ERROR DAP 3 ap_network: Observer 10.10.101.2 is not
accepting TZSP packets
To prevent ICMP error messages from the observer, D-Link recommends using the Netcat
application on the observer to listen to UDP packets on the TZSP port.
Conguring a Snoop Filter
To congure a snoop lter, use the following command:
set snoop filter-name [condition-list] [observer ip-addr] [snap-length num]
The filter-name can be up to 32 alphanumeric characters.
The condition-list species the match criteria for packets. Conditions in the list are ANDed.
Therefore, to be copied and sent to an observer, a packet must match all criteria in the
condition-list. You can specify up to eight of the following conditions in a lter, in any order
or combination:
frame-type {eq | neq} {beacon | control | data | management | probe}
channel {eq | neq} channel
bssid {eq | neq} bssid
src-mac {eq | neq} mac-addr
dest-mac {eq | neq} mac-addr
host-mac {eq | neq} mac-addr
mac-pair mac-addr1 mac-addr2
To match on packets to or from a specic MAC address, use the dest-mac or src-mac option.
To match on both send and receive trafc for a host address, use the host-mac option. To
match on a trafc ow (source and destination MAC addresses), use the mac-pair option.
This option matches for either direction of a ow, and either MAC address can be the source
or destination address.