43-2
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 43 Tracking Host Aging
Understanding How Host Aging is Tracked
Understanding How Host Aging is Tracked
Layer 2 authentication features, 802.1x, and MAC authentication bypass install entries into the CAM
table to ensure packet switching in the hardware. The CAM entries are static and it cannot be ensured
that they are current. The entries age with the hardware if they are not removed by the authentication
feature at the end of the session. If a host leaves before the authentication session expires or if the
authentication manager is not notified about removing the CAM entry, the stale entry remains in the
hardware switching table. Even the Layer 3 protocols, LAN port IP and Web-based proxy authentication
have no method to age out the CAM entry if the host leaves before the session expires.
The IP device-tracking feature, which is included in the authentication manager, tracks the existence of
the host and removes aged entries in the CAM table. The device-tracking feature ensures that the
hardware entries and authentication sessions get aged out. As a result of aging, the hosts are removed
from the EARL.
Configuring IP Device Tracking Globally
When enabled, the IP device tracking feature sends out a probe to check if the host is still present. The
probe can be sent out at regular intervals for a specified number of times. The default is enabled.
To enable or disable IP device tracking globally, perform this task in privileged mode:
This example shows how to enable IP device tracking globally:
Console> (enable)
set ip device-tracking enable
Successfully enabled device tracking.
Console> (enable)
This example shows how to display the current global configuration of IP device tracking:
Console> (enable)
show ip device-tracking
Device tracking mode : Enabled
Device tracking count : 3
Device tracking timeout : 30
Console> (enable)
The following sections describe how to set the probe interval and probe count values:
•
Specifying the IP Device Tracking Interval, page 43-2
•
Specifying the IP Device Tracking Count, page 43-3
Note
The
probe interval
and
probe count
values can only be set globally and are common for all types of
authentication methods.
Specifying the IP Device Tracking Interval
You can set IP device tracking to send a probe at regular intervals (in seconds). The range is from 5 to
65535 seconds. The default is 30 seconds.
Task
Command
Enable or disable IP device tracking globally.
set ip device-tracking
{
disable
|
enable
}
