Some wifi clients have no network access after connecting

[icetim000]

Hello,

I'm experiencing a strange issue where some wifi clients are able to connect to a wireless network and get a valid IP address from the internal DHCP server, but they are unable to access the Inernet or any network devices. I am unable to ping the wifi client from the switch which has the AP attached to it.

This is affecting clients on different access points, but not all wifi clients are affected.

Some wifi clients on the same access point work but some others can't access any resources or the Internet, but do connect successfully and get a valid IP address from the DHCP server.

The wireless network is bridged to the LAN through the firewall.

I've attached a screenshot of the switch as an example showing one of the access points connected to switch port A15 and 2 wifi clients connected to this AP.  Note- not all AP's are connected to this switch.

Why would one of the clients have their mac address registered on port Trk1 and not the port that the AP is connected to (A15)? I checked the AP's and the client is definately connected to that AP.

I cleared the ARP cache on the switch and immediately tried pinging the wifi client from the switch and was successful but then tried another ping again straight away and it was unreachable!

Could it be a roaming issue? Maybe another AP connected to a different switch thinks it has this wifi client connected?

Any ideas?

Thanks

[Georg Pauwen]

Hello,

Trk1 is as far as I recall the abbreviation for a tagged trunk port on an HP switch. Are there any of those in the roaming range of your wifi clients ?

[icetim000]

Sorry I should have mentioned..it's an HP Procurve switch the AP is attached to, not Cisco. I thought I would post here because it seems more of a general networking issue and I know there are a lot of smart folks here!

I'm thinking even though the wifi client is connected to the AP, there is another AP it previously connected (which is connected to a different switch) and for whatever reason the other switch or AP thinks it's still connected to it.

When I'm back in the office i will get all the AP's rebooted and clear the mac address tables on all the switches.

Very strange issue!

[Georg Pauwen]

Hello,

good idea to reboot the devices and clear the MAC table, let us know the results.

[icetim000]

No joy after restarting all the AP's and clearing the ARP cache and MAC address tables on the switches.

It's strange because the wifi clients that have the issue, can actually obtain an IP address (or renew their lease) from the DHCP server when connected, yet I can't even ping their IP address from the switch and they can't access any network resources.

[Georg Pauwen]

Hello,

which VLAN do the clients belong to ? Check if the tagging on the trunk ports between the AP and the HP match (e.g. if the native Vlan is tagged or untagged on both)...

[icetim000]

Hi,

The AP's are untagged and the switchports for the APs are just on VLAN1.

Strangely some clients connected to an AP are able to connect to the network, but not everyone connected to the same AP can.

It's a bit baffling! I'll do some more investigation.

[paul driver]

Hello

I am assuming the TK1 is interconnecting to another switch which has additional APs connected to it?

Access-points especially Meraki's utilise something called meshing, which allows a client be connect to one ap but be registered to another if  the aps own physical connection temporally becomes unavailable from the switch.

This client would then be seen coming from another location.

These wifi clients that are able to recieve a dhcp allocation but not able to reach anything - Do they acutally receive a valid allocation and not a rouge address?

Is it possible you could have rogue dhcp server active?

Have you checked the dhcp server address in the lease to make sure it is actually orignating from the correct server?

res
Paul

[icetim000]

Thanks for everyone's help. This eneded up being caused one of the 2 fibre ports being faulty on one of the switches, causing intermittent issues with the AP's that were connected to the switch. I wasn't initally able to log into that switch, so couldn't see what was going on with it.

[adiazsal]

Hi based on the information you provided us this can be also a Sticky Client Issue because its seems that the second AP you mentioned before, is the one that recognize the devices and these remains connected to this AP. Cisco have  optimize roaming that helps devices to take a better roaming decision.But there is no standard that mandates client roaming behavior

-You can change the mandatory Rates on the Radios and Disable the Lowers Rates and 

Leave mandatory 11 Mbps and starting 12 Mbps and up  have it Enable