Troubleshooting Wireless

Over the time i have been involved in countless issues regarding Wireless Networks, I will try to summarize some of my learnings and the sequenze of troubleshooting. Overall it’s a matter of simplifying as much as possible and start with the easiest things to exclude. Also remember this could be very time consuming (expensive for the customer), so allways start from the buttom.

  • Is it a single/few Clients that have issue
  • Is it time/location related
  • Is it Throughput/accessibility related
  • Is the SSID visible (we don’t use hidden SSID 🙂 )
  • Do Clients associate/authenticate
  • Do Clients get an IP address
  • Is it a roaming issue
  • When does issues start happening
  • Seen on 2,4GHz or/and 5GHz
  • Has anything changed in the Network

When the above questions have been answered, this will give you somekind of an idea where to start. The below points are not in sequence. It depence on the above. But always start with the simpliest:

  • Check Radius server
    • Here you often find Authentication related issue. If using attributes to push ex. vlan, acl’s etc. this is the place to look (remember aaa override then puzzling with attributes).
  • Try simplifying SSID
    • Often when it indicate that issue could be radius or controller settings related, i create a “test” SSID, starting with the basic settings to see if things works and bit by bit allign it to original SSID. This could be aaa override, dot1.x, ip-helper, Fast Transition, PMF etc. Also RF settings could be in play.
  • Are there Controller version related bugs that could cause issue
    • From time to time it is Wireless Controller related 😉
  • Client NIC driver update
    • The never ending story about updating Client NIC driver. I’m not seeing much old drivers out there, these days. Mostly on IoT , Scanners end this type of equipment. Well, when going to have 6GHz in play, i fear this will be more widespread (Remembering back to the early 5GHz days…)
  • What about Wired Client
    • If FlexConnect i often try to put a Wired client in at access vlan (to what it should be Flex’ed into)
  • AP mix
    • A mixing of different AP models ex. Cisco 2800 with 9100 is a no go. Remember: Don’t confuse Client with different technologies when roaming (Like going from AC to AX vice versa)
  • Signal Coverage
    • All Clients like a strong signal. Some more than others. Even then the Controller shows you a desent signal to the client, it’s not the same that the Client is satisfied.
  • Datarate/MCS and different standards
    • In office envirenment this is usual not an issue but in Warehouses etc. with all kinds of legacy equipment, this could have an impact. (here in 2024 i still have customers with Warehouse equipment running 802.11b, wpa1/tkip (again monye talks)
  • Onsite with Wireless tools
    • Use tools like Ekahau and AirCheck to make a Survey. These tools can also do a packet capture (if roaming related you need ex. a multi USB adapter equipt with WiFi adapters to capture on more than one channel at a time.
    • Do a spectrum measurement to make sure nothing obstructs the frequencys. PIR sensors of different types like to use different frequency’s in 2,4GHz and have seen AP’s not moving away from these infected channels.
    • In newer Wireless implementations, Things like Packet Capture, Spectrum Analyzing etc. could be performed directly on AP’s