Alexandr,

The Call Classification field identifies if the Route Pattern will be an off-net or on-net call.

It can be used to block certain calls and features when using an off-net number.

E.g.: You can block a call transfer to an PSTN number to prevent toll fraud.

Cisco Unified CallManager Administration Guide, Release 5.1(3) - Route Pattern Configuration [Cisco Unified Communications Manager (CallManager)] - Cisco Systems - Route Pattern Configuration Settings:

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/5_1_3/ccmcfg/b03rtpat.html#wp1023973

See below an example of how Call Classification is useful:

Cisco Unified CallManager Features and Services Guide, Release 5.0(2) - External Call Transfer Restrictions [Cisco Unified Communications Manager (CallManager)] - Cisco Systems:

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/5_0_2/ccmfeat/fsxfer.html

You can see a topic here, for CMC:

Cisco Systems: Networking Professionals Connection - IP Telephony: Forced Authorization Code VS Client Matter Code:

http://forum.cisco.com/eforum/servlet/NetProf?page=netprof&forum=Unified%20Communications%20and%20Video&topic=IP%20Telephony&topicID=.ee6c829&fromOutline=&CommCmd=MB%3Fcmd%3Ddisplay_location%26location%3D.2cc163d7

Also, a doc from cisco.com site:

Cisco Unified CallManager Features and Services Guide, Release 5.0(2) - Client Matter Codes and Forced Authorization Codes [Cisco Unified Communications Manager (CallManager)] - Cisco Systems:

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/admin/5_0_2/ccmfeat/fsfaccmc.html

Hope this help you!

Vitor