Key Considerations; Discovering Over Slow/Expensive Links - 3Com 3C15500 - Network Director User Manual

Key Considerations

Discovering over
slow/expensive links
Routing: It uses MIB II tables to establish if the device has
IP-forwarding enabled and has interfaces on multiple subnets. If so
it is flagged as a router and will appear on the map at the top level
with a diamond border. See
page 151.
Switching: It attempts to read the dot1dBaseType from the bridge
MIB. If this is present it is flagged as a switch and will appear with
an octagonal border on the map. See
page 151.
For third party switches 3Com Network Director reads bridge FDB tables
during the topology process. However, it does not attempt to retrieve
spanning tree information for these devices.
No attempt is made to determine the topology of third party hubs. They
will simply be treated as end stations by the topology process.
3Com Network Director attempts to determine the manufacturer of third
party devices, only if they support SNMP. However, it does attempt to
determine the type of certain end stations, such as Unix workstations.
If you are discovering a remote subnet over a slow link you may find that
3Com Network Director encounters many timeouts when communicating
with the remote devices. Also, you may find that the traffic generated by
3Com Network Director is consuming a significant amount of the
bandwidth, thus impacting other users of the connection.
If you are concerned about consuming bandwidth, it is generally better to
increase the timeout values 3Com Network Director uses, rather than
increasing the number of retries. By increasing the timeouts, 3Com
Network Director will wait longer for the responses from the devices, and
also by waiting longer it means there are periods during which other
traffic can use the link. Increasing the number of retries would simply
generate more traffic since 3Com Network Director would be resending
its requests while the initial responses are coming back.
If you are less concerned about consuming bandwidth, but more
concerned about the actual time a link is open (i.e. due to its cost) then
you may consider that increasing the number of retries is also an option.
Key Considerations
"Working with the Map"
"Working with the Map"
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