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Cisco Bug: CSCus13594 - AP1700/2700/3700 5GHz: Slow in getting the DHCP address, ARP negotiation failed

Last Modified

Feb 27, 2018

Products (1)

  • Cisco Aironet 3700 Series

Known Affected Releases

8.0(100.0)

Description (partial)

Symptom:
1. the customer use the LAP2700 with the WiSM2 with 8.0.100.0 version.
2. they observed very slow in getting the DHCP IP address in the AP2700 when compare to the old LAP2600.
3. in the sniffer, we found the AP send out the first DHCP OFFER with the wrong sequence number after the ACTION frame. that's why the client seems ignore this packet and will have to retry after around 8 seconds.
4. for the other client, the problem should be same, but different client might try re-send the DHCP discovery  faster and it might be less noticiable.
5. the problem happened on both AP2700 and AP3700.

This defect will cause ARP issue on client. The client may send ARP Request at first then wait for ARP Response from AP. However AP will send invalid ARP Response due to this bug, which result in invalid ARP negotiation. The client cannot get MAC address of default gateway (router) hence it cannot resolve DNS queries, like apple.com, nintendo.net, etc.. This will trigger the client to send Disassociation to AP and you may lose Wi-Fi association. One of the affected clients is Nintendo Switch.

Conditions:
AP1700, 2700, and 3700, 5GHz Wi-Fi network. 2.4GHz should work though.
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