If you wish to set up a call forward on your Cisco 7821, please follow these steps:

Using the Forward soft-key:

STEP 1. On the Cisco 7821 handset - find the Forward soft-key option. 
STEP 2. Press the Forward soft-key and enter a number to which to forward all calls; for example, your voice mailbox, another extension, or an outside line.

Using the star code:

Press *72 on the dial pad and call. Enter the number to which to forward all calls.

Using the settings

STEP 1. Click the Settings button.
STEP 2. Click User Preferences.
STEP 3. Click Call Preferences.
STEP 4. In the 'Forward all number' field enter the number you wish to forward to.

Forwarding Calls When Your Phone is Busy

Using the star code:

Press *90 on the dial pad and call. Enter the number to which to forward calls.

Using the settings

STEP 1. Click the Settings button.
STEP 2. Click User Preferences.
STEP 3. Click Call Preferences.
STEP 4. In the 'Forward busy number' field enter the number you wish to forward to.

Forwarding Calls When You Don’t Answer the Phone

Using the star code:
Press *92 on the dial pad and call. Enter the number to which to forward calls.

Using the settings

STEP 1. Click the Settings button.
STEP 2. Click User Preferences.
STEP 3. Click Call Preferences.
STEP 4. In the 'Fwd no answer number' field enter the number you wish to forward to.

Note: You will see the number currently set to forward to in the top left corner of your LCD screen.

Stopping Call Forwarding

Using the Soft-Key

To stop forwarding calls, press the Clr fwd soft-key.

Using the settings

STEP 1. Click the Settings button.
STEP 2. Click User Preferences.
STEP 3. Click Call Preferences.
STEP 4. Change Call forwarding to Off.