Category: Cisco

Apple iOS 14 Private Address feature, per SSID Wi-Fi MAC randomisation and how it actually works

Apple published a brief summary of the newly introduced “Private Address” Wi-Fi feature. Since it does not go into the detail, I tested the public iOS 14.0 release on an iPhone SE and iPad Mini in my lab. Here is how it actually works.

New Wi-Fi networks

For SSIDs you have not connected to before, iOS 14 devices generate a random MAC “Private Address” and they use this MAC address permanently for this SSID. This address does NOT change over time. This works as expected.

Previously used Wi-Fi networks

Known Wi-Fi networks you have already connected to at least once before the upgrading to iOS 14 get a different treatment though. And this is where things are not as straightforward as the documentation suggests.

After upgrading to iOS 14, I connect to a known network which I have already used before the upgrade. The MAC address that is used is actually the real hardware MAC address of the Wi-Fi adapter for 24 hours. Note that the “Private Address” feature is enabled. This could potentially be considered a UI bug.

24 hours after first connecting from an iOS 14 device to this known SSID, the “Private Address” feature kicks in and the MAC address for this SSID automatically switches from the real MAC address to a randomly generated MAC address. Personally, I assume that this 24-hour period has been developed to allow enterprises to disable Private Address feature on their managed iOS devices using MDM, but I may be wrong.

From this point onwards the same randomly generated Private Address is permanently used for this SSID and does NOT change over time.

Schedule WLAN availability on Catalyst 9800 Series Wireless LAN Controllers

Catalyst 9800 controllers come with built-in support for WLAN availability scheduling. When a WLAN becomes disabled, APs do not broadcast the SSID and channel utilisation decreases. Also, it can be implemented as a security enhancement to prevent client devices from connecting during specified hours.

At the time of writing IOS-XE 17.3.1 does not yet offer a GUI for this capability, but there is a couple of options how to schedule WLAN availability.

Before we start, please double-check time settings on the controller, enable NTP client and set a correct timezone.

Option 1: Built-in Calendar Profile

The configuration is self-explanatory, so let’s start with that. My example enables all WLANs mapped to the “default-policy-profile” from 9 am to 5 pm every week day. Outside of these times, the SSIDs will not be available for clients to join.

configure terminal
!
wireless profile policy default-policy-profile
shutdown
!
no wireless profile calendar-profile name WEEKDAYS-9-TO-5
!
wireless profile calendar-profile name WEEKDAYS-9-TO-5
day monday
day tuesday
day wednesday
day thursday
day friday
recurrence weekly
start 09:00:00 end 17:00:00
!
wireless profile policy default-policy-profile
calendar-profile name WEEKDAYS-9-TO-5
action wlan_enable
no shutdown
!

Verification

You can verify using a Wi-Fi client. If you do “show wlan summary”, the WLANs will still appear as “Enabled” and this is expected. To verify current status of WLANs controlled by the Calendar Profile, please use “show logging | include SCHEDULED_WLAN”.

Reference

Official documentation explaining Calendar Profiles.

Option 2: EEM Script

If you like flexibility, an EEM script running on the controller triggered by CRON might work even better for you. Special thanks to Federico Ziliotto for this.

event manager applet EEM_SCHEDULE_WLAN_UP
event timer cron cron-entry "0 9 * * 1-5" name 9_AM_MON_TO_FRI
action 1.0 cli command "enable"
action 2.0 cli command "conf t"
action 3.0 cli command "wlan MY_SSID"
action 4.0 cli command "no shut"
action 5.0 cli command "end"
action 6.0 syslog msg "Scheduled WLAN_SSID has been enabled"

event manager applet EEM_SCHEDULE_WLAN_DOWN
event timer cron cron-entry "0 17 * * 1-5" name 5_PM_MON_TO_FRI
action 1.0 cli command "enable"
action 2.0 cli command "conf t"
action 3.0 cli command "wlan MY_SSID"
action 4.0 cli command "shut"
action 5.0 cli command "end"
action 6.0 syslog msg "Scheduled WLAN_SSID has been disabled"

Reference

Here and here are some useful and practical EEM examples for your reference.

How to convert hundreds of Cisco Aironet or Catalyst APs from Mobility Express or Embedded Wireless Controller to Lightweight mode using Option 43

You may have used DHCP Option 43 to point an AP to its controller before. But only very few people know that Cisco APs can automatically convert themselves from the built-in controller mode (think Mobility Express or Embedded Wireless Controller) to Lightweight mode after they receive a special Option 43 from a DHCP server.

If you have a pallet of access points (or routers with built-in Wi-Fi in Mobility Express mode) next to your desk and need to convert all of them to Lightweight mode, simply configure DHCP Option 43 in the following format on your DHCP server and plug them into a PoE capable switch. After the APs boot up and receive the option from DHCP server, they automatically switch to the Lightweight mode and attempt to join the configured controller (192.168.130.2 in our case).

Option 43 format used for AP conversion

f2:05:c0:a8:82:02

“f2” tells the AP that we want it to switch to Lightweight mode

“05” means that only one controller IP address will follow

“c0:a8:82:02” is the controller IP address (192.168.130.2 in this case) in hexadecimal format, search for “IP to Hex Converter” if you do no want to do the math

Cisco IOS/IOS-XE DHCP server configuration

You can run DHCP server on a Catalyst switch. The DHCP scope configuration is straightforward. 

ip dhcp pool <pool name>
network <ip network> <netmask>
default-router <default-router IP address>
dns-server <dns server IP address>
option 43 hex f205c0a88202

WLAN Pi, Raspberry Pi and any other Linux ISC DHCP server configuration

Special thanks to Nicolas Darchis, who helped me find the “vendor-encapsulated-options” option. It lets you enter Option 43 in the hex format and all it takes is a single line of DHCP server configuration.

# eth0 DHCP scope on ISC DHCP server
subnet 192.168.130.0 netmask 255.255.255.0 {
interface eth0;
range 192.168.130.100 192.168.130.200;
option routers 192.168.130.1;
option domain-name-servers 208.67.222.220, 208.67.222.220;
default-lease-time 86400;
max-lease-time 86400;
option vendor-encapsulated-options f2:05:c0:a8:82:02;
}

DHCP server on Cisco Meraki MX appliance

If your DHCP server runs on a Cisco Meraki MX appliance, you can easily configure Option 43 using Dashboard. Here are the instructions.

Packet capture or it did not happen

Here is the DHCP Offer packet with the special Option 43 value sent from DHCP server to the APs. They will start the conversion automatically after receiving it.

Option 43 which converts the AP from ME or EWC mode to lightweight

Verify successful AP conversion to Lightweight mode

Console to one of the APs and you will notice this message:

[*08/25/2020 23:24:39.5620] Last reload reason : 2: AP type changed from ME to CAPWAP

Or you can let the AP finish its job. And then verify successful conversion to Lightweight mode whenever you are ready using the “show version” command.

9120#show version
<output omitted>
9120 uptime is 0 days, 0 hours, 5 minutes
Last reload time : Tue Aug 25 23:24:39 UTC 2020
Last reload reason : AP type changed from ME to CAPWAP
<output omitted>

Cisco Aironet and Catalyst AP Option 43 configuration for ISC DHCP server on Linux

There is great document explaining how to configure Option 43 on ISC DHCP server on the Cisco website.

If all you need is a simple DHCP server which will assign Option 43 to all devices on the network, without selectively assigning it only to specific AP models using the class construct, you can simplify your ISC DHCP server configuration to this. It works great on a WLAN Pi.

Configuration

# Linux ISC DHCP server configuration in /etc/dhcp/dhcpd.conf
option space Cisco_LWAPP_AP;
option Cisco_LWAPP_AP.server-address code 241 = array of ip-address;

# eth0 DHCP scope
subnet 192.168.73.0 netmask 255.255.255.0 {
interface eth0;
range 192.168.73.100 192.168.73.200;
option routers 192.168.73.1;
option domain-name-servers 208.67.222.222, 208.67.220.220;
default-lease-time 86400;
max-lease-time 86400;
vendor-option-space Cisco_LWAPP_AP;
option Cisco_LWAPP_AP.server-address 10.10.10.10, 10.20.20.20;
}

Verification

The access point will get its IP configuration from the DHCP server including Option 43 and will try to join these controllers.

Configure DHCP Option 43 on Cisco Meraki MX appliance to point AP to its WLC

Here is how to configure Option 43 on an MX appliance for a Cisco Aironet or Catalyst AP to discover its Wireless LAN Controller (WLC).

My Catalyst 9800-CL controller IP address: 173.38.219.33

Meraki MX appliance DHCP server configuration

Format of the hex string

In my example, the final string would be “f1:04:ad:26:db:21”

“f1:04” tells the AP that only one WLC IP address is used, followed by the actual address
“ad” is hex representation of 173
“26” is hex representation of 38
“db” is hex representation of 219
“21” is hex representation of 33

Verification on the AP

Two controllers

If you provide the AP with IP addresses of 2 standalone controllers (think N+1 HA mode), then simply change “f1:04” to “f1:08” and append the second controller’s IP address in hex representation to the end of the hex string.

Primary controller IP address: 173.38.219.33
Secondary controller IP address: 173.38.219.34
Hex string: f1:08:ad:26:db:21:ad:26:db:22

How to install Cisco vWLC in VMware Fusion on your Mac

Officially, vWLC is not supported on Type-2 hosted hypervisors like Fusion or Workstation. However, if you need to build a non-production lab, portable demo or practice for your next exam, technically you can run vWLC in VMware Fusion.

The trick is to install Fusion on your Mac, create a new VM with the free ESXi Hypervisor (or the full-blown one if you have licenses) and deploy vWLC onto the ESXi:

macOS <-> VMware Fusion <-> ESXi Hypervisor running as a VM <-> vWLC VM

It may sound complex, but is actually quite easy to do and runs like a charm even on a 13″ Intel i5 MacBook Pro.

  1. Download the vWLC OVA image from Cisco.com.
  2. Download VMware vSphere Hypervisor 6.7 ISO. Register on their website to get a free license key.
  3. Download the ovftool 4.3.0 (older versions may not work correctly) for Windows and make sure you have a Windows machine or VM by hand as ovftool only runs on Windows.
  4. Create a new VM in VMware Fusion, mount the Hypervisor ISO and install ESXi. Configure networking for this VM as Bridged Networking to Wi-Fi or Ethernet. Wi-Fi is a great option as it allows you to move freely with your Mac whilst running the vWLC.
    VMware-Fusion-adapter-settings
  5. With the free ESXi Hypervisor, we have to deploy the vWLC OVA using the ovftool. This will help us get past the errors we would have otherwise ran into the ESXi web GUI. To do this we need a Windows machine.
  6. Install the ovftool in the Windows machine, transfer the vWLC OVA archive to it and deploy the OVA onto ESXi:

    C:\Program Files\VMware\VMware OVF Tool>ovftool.exe –skipManifestCheck –acceptAllEulas –noSSLVerify –noSSLVerify=true -ds=”datastore1″ –net:”VM Network”=”VM Network” –net:”VM Network 2″=”VM Network” C:\Users\Jiri\Desktop\AIR_CTVM-K9_8_5_151_0.ova vi://192.168.196.136

    The IP address in this string “vi://192.168.196.136” is our ESXi address. You may have noticed that I am using the same network for both Service Port and Management interfaces. After I deploy the OVA, I usually disable the Service Port adapter in the VM settings and use Management interface for management and for APs to join. It just keeps things simple and we don’t need to worry about multiple adapters and subnets.

  7. You can set the vWLC VM to Autostart and start it manually now.
  8. Open Console to it and press any key to activate the console access.
  9. Follow the installation guide.
  10. If you are running the evaluation license, accept the EULA. If you purchased AP licenses, add then to the controller and accept the EULA.
  11. Since vWLC only supports Flexconnect mode APs, make sure to convert your APs manually or apply this CLI command:

    config ap autoconvert flexconnect

    Autoconvert-APs-to-Flexconnect-mode

  12. Finally connect your AP to a PoE capable switch or power injector and it should be able to discover and join the virtual controller.
    vWLC-ESXi-Fusion

Note: If you installed vWLC VM directly onto Fusion with no ESXi Hypervisor layer, the controller would not be able to communicate on its Management interface.

Catalyst 9800-CL IOS-XE controller

The above scenario covers the AireOS vWLC. Cisco now has a complete range of Catalyst 9800 series controllers with feature parity between them. The new virtual controller is called Catalyst 9800-CL and it brings all the great IOS-XE features, HA SSO, programmability, hot patching and supports all AP modes.

Francois and Rowell published great step by step instructions on how to install C9800-CL onto ESXi and Fusion.

CCNP#1 zdoláno, příští týden začínáme CCNP#2

Dnes jsem složil poslední test CCNP#1 semestru v rámci Cisco Networking Academy. Díky Alefu a Ciscu studuji tyto kurzy v rámci programu nazvaného CCIE Inkubátor. Tímto jim děkuji za podporu.  Hned příští čtvrtek začínám další semestr studia. Tento byl věnován Advanced Routingu, příští je zaměřen na Switching.