Wireless Troubleshooting · Topic 1 of 3

Client Troubleshooting and the Registration Table

Learn a step by step method to troubleshoot wireless clients, read the registration table, and use the wireless log to find why a client cannot connect.

  • 5 min
In a nutshell
  • The registration table lists the clients that are associated to an access point.
  • A client that is in the table has completed the join, so look at addresses and higher layers.
  • A client that is not in the table needs radio, security, access list and log checks.

What it is

Client troubleshooting is the process of finding out why a wireless client cannot connect or performs badly.

The main tool on an access point is the registration table. It lists every client that is currently associated, with the signal and the data rates of each one.

A good method saves time. You work from the symptom to the layer where the fault is, instead of changing settings at random.

Symptomcannot join or slowcheckRegistration tableis the client listedthenLogwhy it failedfixSettingchannel, key, list

How it works

The first question is whether the client appears in the registration table.

Sort the symptom

SymptomLikely area
The client does not see the SSIDBand, channel, country, hidden SSID or distance
The client sees it but fails to joinSecurity settings or the access list
The client joins but gets no addressDHCP or bridge configuration
The client joins but is slow or dropsSignal, noise, interference or data rates

The registration table

/interface wireless registration-table print
/interface wireless registration-table print stats

The table shows one line for each associated client. Useful columns include:

  • the interface and the MAC address of the client
  • the signal strength
  • the transmit and receive rates
  • the uptime
  • the connection quality values

On the wifi driver the table is at /interface wifi registration-table print and shows the same kind of information.

Reading the result

If the client is in the table, the radio link and the security worked. Look at the layers above. Check the rates, the signal and the addresses.

If the client is not in the table, it never completed the join. Look at the radio and security settings, the access list and the log.

Exam tip

A client that is in the table but cannot reach anything points to an address or bridge problem, not a wireless problem.

Checks when the client cannot join

Work through these checks in order.

  1. Is the interface enabled, and is it in the right mode?
  2. Do the client and the access point share a band and a channel width that the client supports?
  3. Is the country setting allowing the channel the access point uses?
  4. Do the security profiles match, including the passphrase?
  5. Does an access list entry reject the client?
  6. Is the client far away, or is the signal weak?

The wireless log

Turn on logging for the wireless topic to see join and leave messages.

/system logging add topics=wireless
/log print where topics~"wireless"
  • /system logging add topics=wireless sends wireless messages to the log.
  • /log print with a filter shows only the wireless entries.

Messages usually mention the client MAC address and a short reason. A key exchange or handshake timeout can point to a wrong passphrase. A reason that names the access list can point to a rejecting rule.

The exact wording depends on the RouterOS version.

Checks when the client is slow

When the client joins but performance is poor, check:

  • the signal strength and the noise
  • the data rates in the registration table
  • other clients that use the airtime
  • interference from other networks and devices

A low rate with a good signal can mean interference. A low rate with a weak signal means the client is too far, or something blocks the path.

Checks above the radio

If the radio link is healthy, test the rest of the path.

/ip dhcp-server lease print
/interface bridge port print
/ping 192.168.88.1
  • lease print shows whether the client received an address.
  • bridge port print shows whether the wireless interface is in the bridge.
  • ping from the router tests basic reachability.

Change one thing at a time

Change one setting, then test again. If you change several settings at once, you cannot tell which one fixed or broke the network.

Record what you changed so you can undo it.

Watch out

Do not clear the access list or change the security profile on a live network without a plan. You may disconnect every client.

What to remember for the exam

Seven facts cover this topic.

  • The registration table lists the clients that are associated to an access point.
  • A client that is in the table has completed the join, so look at addresses and higher layers.
  • A client that is not in the table needs radio, security, access list and log checks.
  • /interface wireless registration-table print shows signal, rates and uptime for each client.
  • The wireless log topic shows join and leave reasons.
  • A key exchange timeout can point to a wrong passphrase.
  • Change one setting at a time and test after each change.

Common mistakes

These four errors are common.

Blaming the radio for an address problem. A client in the table with no address needs DHCP and bridge checks.

Changing many settings at once. You will not know which change helped.

Ignoring the log. The log often names the reason for the failure.

Forgetting the access list. A rejecting rule is easy to miss.

Check yourself

Work through these three questions.

  • What does it mean if a client is listed in the registration table but has no network access?

    The client completed the radio join and the security. The fault is above the radio, such as DHCP or the bridge.

  • How do you see why a client was disconnected?

    Add logging for the wireless topic, then use /log print with a filter. The messages name the client and a reason.

  • Why should you change only one setting at a time?

    You can then tell which change fixed or broke the network. Record each change so you can undo it.

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