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WAP321 - Clients losing connection to DHCP server

vasco.cardoso
Level 1
Level 1

I have 4 WAP321 with Single Point Setup configured at a site.

Serving DHCP is a Cisco 891f Router.

Randomly throughout the day, random clients (being laptops, phones, what have you) will lose connection to the network. They are still connected to the AP, but can't ping anything. Issuing a "ipconfig /renew" command on windows will return a "Lost access to DHCP server" (or something of the sort).

APs are updated to the latest firmware (which solves this issue: "CSCus75139 — WAP321 Intermittently wireless client doesn't get IP from DHCP server" ).

There are no logs on either the APs or the router.

Any idea of what could be causing this? Some setting or configuration?

7 Replies 7

slstratt
Level 1
Level 1

Hi vasco.cardoso,

Thank you for using the Small Business Support Community!

Whenever this issue occurs, what steps do you take to restore connectivity? What devices do you need to reset, if any?

Since you say that Windows loses access to the DHCP server, which is located on your router, my initial guess would be that something in your router's configuration is causing your problem.

If you have any other questions, don't hesitate to post them here.

Best,

Taylor

Hi slstratt,

To restore connectivity we take one of two options:

1. Wait it out. The PC usually recovers access to the network after a few seconds/minutes (but it can take up to 30m)

2. Restart the wireless interface of the computer (Either by turning the wifi card off and on, or by reconnecting to the SSID)

I've also noticed a specific behavior when the issue happens, which is that the computer loses the ARP entry for the default gateway. It will then broadcast ARP request packets, to which the router replies, but they don't arrive at the computer (I know this from the ARP logs from the router).

From this information i'm not exactly sure that the issue is with the router, it could be that the APs are blocking (somehow) the arp reply packets.

Hi vasco.cardoso,

After looking into your issue, I found a possible workaround. If this problem is affecting all of the SSIDs on your AP (it sounds like it does), try configuring your DHCP server to use unicast messages. If this doesn't work, then the only other workaround I have is to reboot the device.

I realize that this isn't an ideal solution, but I'd like to let you know that this sounds like it's a known issue for the WAP321. Hopefully this will solve the problem.

Let me know how it works out!

Taylor

Hi slstratt,

Do you happen to know what the IOS commands for such settings are?

I can't seem to find it in the documentation (we're using a Cisco 891f router as DHCP server)

Hi vasco.cardoso,

Unfortunately I couldn't find any documentation specific to the Cisco 891f in regards to IOS commands. I've asked my supervisors, and will post back here as soon as they get back to me.

Taylor

Hi vasco.cardoso,

To get the IOS commands for the Cisco 891f router, try repeating your request over on the Small Business Routers forum. Someone over there should be knowledgeable enough to help you.

In addition, I found a rather thorough website that lists all IOS commands, which you can peruse here.

Best,

Taylor

tgomillion1
Level 1
Level 1

Hi Vasco,

I was having this problem as well. I upgraded to the new firmware but the exact same problem still occurred. I would suggest doing a full factory reset AFTER installing the new firmware. Once I did a factory reset the problem appears to have gone away. My initial thinking was that the firmware update might have also performed some sort of pseudo or partial factory reset, but apparently it did not. If this does fix your issue then please update this thread. Maybe Cisco can add a note about performing a factory reset after the firmware upgrade.

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