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Cisco Bug: CSCvi67049 - IOS AP DHCP During AP PnP Leading to DHCP IP Pool Exhaustion - Windows BAD_ADDRESS

Last Modified

Apr 11, 2018

Products (1)

  • Cisco Aironet 3700 Series

Known Affected Releases


Description (partial)

IP address pool getting exhausted in DHCP scopes on Windows servers.  IP addresses show as "BAD_ADDRESS" with "This address is already in use".

IOS APs running on recovery images doing Plug-and-Play (PNP) and APs are not able to register successfully with the PnP server. APs are continually getting new IP addresses which are exhausting DHCP IP Pool.

1. This happens when the AP loses connectivity. The AP sends 3 DHCP release packets to the server before purging the IP.
2. The Microsoft DHCP server receives the 1st DHCP release packet and assigns the IP to some other host, which the AP detects as conflict and reports.
3. Sending 3 DHCP releases is because DHCP IETF standard defines release as a UDP packet, which does not have any ACK. So to play it safe, ALL IOS devices send 3 DHCP releases, but only Microsoft's server causes this issue.
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