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Revision as of 14:41, 18 February 2014 by Mplsguy (talk | contribs)
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Controlled Access Point system (CAPs) allows to centralize wireless network management and, if necessary, data processing. When using CAPs feature, network consists of number of Access Points (CAP) that provide wireless connectivity and manager (CAPs Manager) that manages AP configuration, takes care of client authentication and optionally data forwarding.

When CAP is controlled by Manager it only requires configuration that allows it to establish connection with Manager. Functions that were conventionally executed by AP (like access control, client authentication) are now executed by Manager. CAP merely takes care of wireless link layer encryption/decryption. Depending on configuration, data is either forwarded to Manager for centralized processing or forwarded locally at CAP.

CAPs Manager features

  • RADIUS MAC authentication
  • WPA/WPA2 security
  • TBA

MISSING CAPs Manager features

  • Nstreme AP support
  • Nv2 AP support
  • TBA

CAP to CAPs Manager Connection

To operate in CAP system and provide wireleless connectivity, CAP must establish management connection with CAPs Manager. Management connection can be established using MAC or IP layer protocols and is secured using DTLS.

CAP also establishes data connection with Manager, but data connection is not secured. If deemed necessary, other means to secure data need to be used, e.g. IPSec or encrypted tunnels.

CAP to CAPs Manager connection can be established using 2 transport protocols.

  • MAC layer connection features:
    • no IP configuration necessary on CAP
    • CAP and Manager must be on the same Layer 2 segment - either physical or virtual (by means of L2 tunnels)
  • IP layer (UDP) connection features:
    • can traverse NAT if necessary
    • CAP must be able to reach Manager using IP
    • if CAP is not on the same L2 segment as Manager, it must be provisioned with Manager IP address, because IP multicast based discovery would not work

In order to establish connection with Manager, CAP executes discovery process. During discovery CAP attempts to contact Managers and builds available Manager list. CAP attempts to contact available Managers using:

  • configured list of Manager IP addresses
  • list of Manager IP addresses obtained from DHCP server
  • broadcasting on configured interfaces using both - IP and MAC layer protocols.

When list of available Managers is built, CAP selects Manager based on the following precedence list:

  • Managers with MAC layer connectivity
  • other Managers.

After Manager is selected, CAP attempts to establish DTLS connection. There are the following authentication modes possible:

  • no certificates on CAP and Manager - no authentication
  • only Manager is configured with certificate - CAP authenticates Manager
  • CAP and Manager are configured with certificates - mutual authentication

CAP Configuration

When AP is configured to be controlled by Manager, configuration of selected wireless interfaces entered on AP is ignored. Instead, AP accepts configuration for selected wireless interfaces from Manager.

CAP behaviour of AP is configured in /interface wireless cap menu. It contains the following settings:

Property Description
enabled (yes | no; Default: no) Disable or enable CAP feature
interfaces (list of interfaces; Default: empty) List of wireless interfaces to be controlled by Manager
certificate (certificate name | none; Default: none) Certificate to use for authenticating
discovery-interfaces (list of interfaces; Default: empty) List of interfaces over which CAP should attempt to discover Manager
static-caps-manager-addresses (list of IP addresses; Default: empty) List of Manager IP addresses that CAP will attempt to contact during discovery
bridge (bridge interface; Default: none) Bridge to which interfaces should be added when local forwarding mode is used

CAPs Manager Configuration Concepts

Each wireless interface on CAP that is under CAPs Manager control appears as virtual interface on CAPs Manager. This provides maximum flexibility in data forwarding control using regular RouterOS features, such as routing, bridging, firewall, etc.

Multitude of wireless interface settings are grouped in named groups (profiles) that simplifies the reuse of configuration - for example, common configuration settings can be configured in configuration profile and multiple interfaces can refer to that profile. At the same time any setting can be overridden directly in interface configuration for maximum flexibility.

Currently there are the following setting groups:

  • channel - channel related settings, such as frequency and width
  • datapath - data forwarding related settings, such as bridge to which particular interface shoul$
  • interworking - IEEE 802.11u, Hotspot 2.0 related settings
  • security - security related settings, such as allowed authentication types or passphrase
  • configuration - main wireless settings group, includes settings such as SSID, and additionally binds together other setting groups - that is, configuration profile can refer to channel, security, etc. named setting groups. Additionally any setting can be overridden directly in configuration profile.

Interface settings bind together all setting groups, but additionally any setting can be overridden directly in interface settings.

By means of setting groups, configuration is organized in hierarchical structure with interface (actual user of configuration) as root. In order to figure out effective value of some setting this structure is consulted in a fashion where higher level setting value overrides lower level value.

For example, when WPA2 passphrase to be used by particular interface needs to be found, the following places are consulted and the first place with WPA2 passphrase configured specifies effective passphrase. "->" denotes referring to setting profile (if configured):

  • interface passphrase
  • interface->security passphrase
  • interface->configuration passphrase
  • interface->configuration->security passphrase

There are 2 types of interfaces on CAPs Manager - "master" and "slave". Master interface holds configuration for actual wireless interface (radio), while slave interface links to master interface and is intended to hold configuration for Virtual-AP (multiple SSID support). There are settings that are meaningful only for master interface, mainly hardware setup related settings such as radio channel settings. Note that in order for radio to be accepting clients, its master interface needs to be enabled. Slave interfaces will become operational only if enabled and master interface enabled.

Interfaces on CAPs Manager can be static or dynamic. Static interfaces are stored in RouterOS configuration and will persist across reboots. Dynamic interfaces exist only while particular CAP is connected to CAPs Manager.

CAPs Manager Global Configuration

Settings to enable CAPs Manager functionality are found in /caps-manager manager menu:

Property Description
enabled (yes | no; Default: no) Disable or enable CAPs Manager functionality
certificate (certificate name | none; Default: none) Device certificate
require-peer-certificate (yes | no; Default: no) Require all connecting CAPs to have valid certificate

Radio Provisioning

CAPs Manager distinguishes between CAPs based on identifier. Identifier is generated based on the following rules:

  • if CAP provided certificate, identifier is set to Common Name field in certificate
  • otherwise identifier is based on Base-MAC provided by CAP in form: '[XX:XX:XX:XX:XX:XX]'.

When DTLS connection with CAP is successfully established (which means that CAP identifier is known and valid), CAPs Manager makes sure there is no stale connection with CAP using the same identifier. Currently connected CAPs are listed in /caps-manager remote-cap menu:

[admin@CM] /caps-manager> remote-cap print
 # ADDRESS                                    IDENT           STATE               RADIOS
 0 00:0C:42:00:C0:32/27044                    MT-000C4200C032 Run                      1

CAPs Manager distinguishes between actual wireless interfaces (radios) based on their builtin MAC address (radio-mac). This implies that it is impossible to manage two radios with the same MAC address on one CAPs Manager. Radios currently managed by CAPs Manager (provided by connected CAPs) are listed in /caps-manager radio menu:

[admin@CM] /caps-manager> radio print
Flags: L - local, P - provisioned 
 #    RADIO-MAC         INTERFACE                               REMOTE-AP-IDENT
 0  P 00:03:7F:48:CC:07 cap1                                    MT-000C4200C032

When CAP connects, CAPs Manager at first tries to bind each CAP radio to CAPs Manager master interface based on radio-mac. If appropriate interface is found, radio gets set up using master interface configuration and configuration of slave interfaces that refer to particular master interface. At this moment interfaces (both master and slaves) are considered bound to radio and radio is considered provisioned.

If no matching master interface for radio is found, CAPs Manager executes provisioning rules. Provisioning rules is ordered list of rules that contains settings that specify what radio to match and settings that specify what action to take if radio matches. Provisioning rules are configured in /caps-manager provisioning menu:

[admin@CM] /caps-manager provisioning> print
Flags: X - disabled 
 0   radio-mac=00:00:00:00:00:00 action=create-enabled master-configuration=main-cfg 

Radio can be matched by provisioning rule based on the following settings:

  • radio-mac - MAC address of radio, empty MAC (00:00:00:00:00:00) means match all MAC addresses
  • TBA more matchers

Action to take if rule matches is specified by the following settings:

  • action
    • create-disabled - create disabled static interfaces for radio, as a interfaces will be bound to radio, but radio will not be operational until interface will be manually enabled;
    • create-enabled - create enabled static interfaces, as a result interfaces will be bound to radio, and radio will be operational;
    • create-dynamic-enabled - create enabled dynamic interfaces, as a result interfaces will be bound to radio, and radio will be operational;
    • none - do nothing, leaves radio in non-provisioned state;
  • master-configuration - if action specifies to create interfaces, new master interface with its configuration set to this configuration profile is created
  • slave-configurations - if action specifies to create interfaces, new slave interface for each configuration profile in this list is created.

If no rule matches radio, implicit default rule with action create-enabled and no configurations set is executed.

For user's convenience there are commands that allow to re-execute provisioning process for some radio or all radios provided by some AP:

[admin@CM] > caps-manager radio provision 0


[admin@CM] > caps-manager remote-cap provision 0

Interface Configuration

CAPs Manager interfaces are managed in /caps-manager interface menu:

[admin@CM] > /caps-manager interface print          
Flags: M - master, D - dynamic, B - bound, X - disabled, I - inactive, R - running 
 #      NAME                                 RADIO-MAC         MASTER-INTERFACE                               
 0 M BR cap2                                 00:0C:42:1B:4E:F5 none                                           
 1   B  cap3                                 00:00:00:00:00:00 cap2                   

Registration Table

Registration table contains list of clients that are connected to radios controlled by CAPs Manager and is available in /caps-manager registration-table menu:

[admin@CM] /caps-manager> registration-table print
 # INTERFACE                   MAC-ADDRESS       UPTIME                RX-SIGNAL
 0 cap1                        00:03:7F:48:CC:0B 1h38m9s210ms                -36


Create security profile for WPA2 PSK, without specifying passphrase:

[admin@CM] /caps-manager security>add name="wpa2psk" authentication-types=wpa2-psk encryption=aes-ccm

Create configuration profile to be used by master interface

  • specify WPA2 passphrase in configuration
  • specify channel settings in configuration:
[admin@CM] /caps-manager configuration> add name=master-cfg ssid=master security=wpa2psk
security.passphrase=12345678 channel.frequency=5180 channel.width=20

Create configuration profile to be used by virtual AP interface

  • specify different WPA2 passphrase in configuration:
[admin@CM] /caps-manager configuration> add name=slave-cfg ssid=slave security=wpa2psk

Create provisioning rule that matches any radio and creates dynamic interfaces using master-cfg and slave-cfg:

[admin@CM] /caps-manager provisioning> add action=create-dynamic-enabled master-configuration=master-cfg

Now when AP connects and is provisioned 2 dynamic interfaces (one master and one slave) will get created:

[admin@CM] /caps-manager interface> print detail 
Flags: M - master, D - dynamic, B - bound, X - disabled, I - inactive, R - running 
 0 MDB  name="cap1" mtu=1500 l2mtu=2300 radio-mac=00:0C:42:1B:4E:F5 master-interface=none 

 1  DB  name="cap2" mtu=1500 l2mtu=2300 radio-mac=00:00:00:00:00:00 master-interface=cap1 

Consider that AP, that does not support configured frequency connects and can not become operational:

[admin@CM] /caps-manager interface> pr
Flags: M - master, D - dynamic, B - bound, X - disabled, I - inactive, R - running 
 #      NAME                                 RADIO-MAC         MASTER-INTERFACE                               
 0 MDB  ;;; unsupported band or channel
        cap3                                 00:0C:42:1B:4E:FF none    

We can override channel settings for this particular radio in interface settings, without affecting master-cfg profile:

[admin@CM] /caps-manager interface> set cap3 channel.frequency=2142