Symptom
When ARP request/Reply packets enter an access or trunk interface and its L2 switched to an another access or trunk interface in same VLAN the ARP request/Reply packets gets duplicated. This means that when one ARP packet enter the switch two identical ARP packets exit the switch. We have seen IP Packets getting duplicated. This only seems to affect ARP packets.
Conditions
L2 switching with lanbase license
Workaround
The issue is only observed with "lanbase" license. Issue is not seen with "ipbase" license.
Enable IPDT
3850-STACK#sh ip device tracking all
Global IP Device Tracking for clients = Disabled >>>>> IPDT is disabled by default on lanbase
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IP Address MAC Address Vlan Interface Probe-Timeout State Source
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3850-STACK(config)#int range gig1/0/19 , gig2/0/39
3850-STACK(config-if)#ip device tracking maximum ?
Maximum devices (0 means disabled)
3850-STACK(config-if-range)#ip device tracking maximum 20
3850-STACK(config-if-range)#end
3850-STACK#sh ip device tracking all
Global IP Device Tracking for clients = Enabled >>>>> Make sure IPDT is enabled
Global IP Device Tracking Probe Count = 3
Global IP Device Tracking Probe Interval = 30
Global IP Device Tracking Probe Delay Interval = 0
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IP Address MAC Address Vlan Interface Probe-Timeout State Source
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Total number interfaces enabled: 2
Enabled interfaces:
Gi1/0/19, Gi2/0/39
Further Problem Description
none
