The Cisco 1921 builds on the best-in-class offering of the Cisco 1841 Integrated Services Routers. All Cisco 1900 Series Integrated Services Routers offer embedded hardware encryption acceleration, optional firewall, intrusion prevention, and advanced security services. In addition, the platforms support the industry's widest range of wired and wireless connectivity options such as Serial, T1/E1, xDSL, Gigabit Ethernet, and third-generation (3G) wireless

http://www.cisco.com/en/US/prod/collateral/voicesw/ps6789/ps7290/ps10589/data_sheet_c78-598389.html

The Cisco 1941 Integrated Services Router (ISR) delivers highly secure data, mobility, and application services. Key features include:

•2 integrated 10/100/1000 Ethernet ports
•2 enhanced High-Speed WAN Interface Card slots that can host 2 single wide or 1 double wide and 1 single wide (e)HWIC
•1 Internal Services Module slot
•Fully integrated power distribution to modules supporting 802.3af Power over Ethernet (PoE) and Cisco Enhanced PoE
•Security

      •Embedded hardware-accelerated VPN encryption
      •Secure collaborative communications with Group Encrypted Transport VPN, Dynamic Multipoint VPN, or Enhanced Easy VPN
      •Integrated threat control using Cisco IOS Firewall, Cisco IOS Zone-Based Firewall, Cisco IOS IPS, and Cisco IOS Content Filtering
      •Identity management that uses authentication, authorization, and accounting (AAA), and public key infrastructure

http://www.cisco.com/en/US/products/ps10545/index.html

Cisco 2900 Series builds on the best-in-class offering of the existing Cisco 2800 Series Integrated Services Routers by offering four platforms:  the Cisco 2901, 2911, 2921, and 2951 Integrated Services Routers.

All Cisco 2900 Series Integrated Services Routers offer embedded hardware encryption acceleration, voice- and video-capable digital signal processor (DSP) slots, optional firewall, intrusion prevention, call processing, voicemail, and application services. In addition, the platforms support the industries widest range of wired and wireless connectivity options such as T1/E1, T3/E3, xDSL, copper and fiber GE.

http://www.cisco.com/en/US/prod/collateral/routers/ps10537/data_sheet_c78_553896.html

Cisco 1900 Series Integrated Services Routers (ISR) are designed to meet the application demands of today's small branches and to evolve to cloud-based services. They deliver virtualized applications and highly secure collaboration through the widest array of WAN connectivity at high performance that offers concurrent services at up to 25 Mbps.

http://www.cisco.com/en/US/products/ps10538/index.html

The Cisco 2951 Integrated Services Router (ISR) delivers highly secure data, voice, video, and application services for small offices. Key features include:
• 3 integrated 10/100/1000 Ethernet ports with 1 port capable of RJ-45 or SFP connectivity
• 2 service module slots
• 4 Enhanced High-Speed WAN Interface Card slots
• 3 onboard digital signal processor (DSP) slots
• 1 internal service module slot for application services
• Fully integrated power distribution to modules supporting 802.3af Power over Ethernet (PoE) and Cisco Enhanced PoE

http://www.cisco.com/en/US/products/ps10539/index.html

The Cisco 2921 Integrated Services Router (ISR) delivers highly secure data, voice, video, and application services for small offices. Key features include:
• 3 Integrated 10/100/1000 Ethernet ports with 1 port capable of RJ-45 or SFP connectivity
• 1 service module slot
• 4 Enhanced High-Speed WAN Interface Card (EHWIC) slots
• 3 onboard digital signal processor slots
• 1 internal service module slot for application services
• Fully integrated power distribution to modules supporting 802.3af Power over Ethernet (PoE) and Cisco Enhanced PoE

http://www.cisco.com/en/US/products/ps10539/index.html

The Cisco 2911 Integrated Services Router (ISR) delivers highly secure data, voice, video, and application service. Key features include:
• 3 integrated 10/100/1000 Ethernet ports (RJ-45 only)
• 1 service module slot
• 4 enhanced high-speed WAN interface card slots
• 2 onboard digital signal processor (DSP) slots
• 1 Internal Service Module slot for application services

http://www.cisco.com/en/US/products/ps10539/index.html

The Cisco 2901 Integrated Services Router (ISR) delivers highly secure data, voice, video, and application services for small offices. Key features include:
• 2 integrated 10/100/1000 Ethernet ports
• 4 enhanced high-speed WAN interface card slots
• 2 onboard digital signal processor (DSP) slots
• 1 onboard Internal Service Module for application services
• Fully integrated power distribution to modules supporting 802.3af Power over Ethernet (PoE) and Cisco Enhanced PoE

http://www.cisco.com/en/US/products/ps10539/index.html