ip device tracking probe delay

[jithu p]

Hi,

 "'ip device tracking probe delay 10 "" , will it means that ,  normally   cisco device (switch or router or firewall) automatically generate the ARP and if this command given it delays for 10 sec ? or it will delay the the unknown flooding for 10 sec ?

[nkarthikeyan]

Hi Jithu,

It actually delay the proble from switch or router for 10 seconds during that time Windows server can sort out the duplicate ip issue detection.

Explanation from Cisco Site:

ip device tracking probe delay 10

The RFC specifies a ten−second window for duplicate address detection, so if you delay the

device−tracking probe, it resolves the issue in nearly all cases. In addition to probe−delay, the delay

also resets when the switch detects a probe from the PC. For example, if the probe timer has counted

down to five seconds and detects an ARP Probe from the PC, the timer resets back to ten seconds. In

rare circumstances, the PC sends an ARP Probe milliseconds before the switch sends its probe, which

still triggers a duplicate address message to the end user. This command was introduced in Version

15.0(1)SE on 2900, 3500, and 3700 Series switch platforms, Version 15.0(2)SG on the 4500 Series

switch platform, and Version 12.2(33)SXI7 on the 6500 Series switch platform.

HTH

Regards

Karthik

[jithu p]

Thanks Karthik ,

 From where the switch gets arp probes , will it automatically generate ? , i know switch will send gratuitous arp if HSRP is enabled , if hasrp is disabled why the switch sends arp until and unless an unknown unicast ocure , please help....

[nkarthikeyan]

Hi Jithu,

All i understand from my above post and RFC for arp probes and gratuitous arp..... if a hosts gets a duplication of address for example say 2 hosts announces that it has the ip address x.x.x.x.... since the arp reply happens unicast other host will not come to know the conflict..... for that there is a workaround to have the arp reply/ack also should happen broadcast..... in such cases delay of 10 sec to probe the hosts.... the hosts will get the conflict of IP address corrected.... So duplication issue and blockage is avoided.

http://www.itcertnotes.com/2011/08/windows-xp-and-windows-7-gratuitous.html

Refer RFC 5227 & 826 for better understanding.

HTH

Regards

Karthik