Cisco 900 Series ISR C921-4P Dual GE WAN Router, 4-Port GE LAN
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PRODUCT DESCRIPTION
Cisco 900 Series Integrated Services Router, Gigabit Ethernet Security Router with Internal Power Supply (C921-4P) — Local Warranty
Compact branch router on Cisco IOS
The Cisco C921-4P belongs to the Cisco 900 Series Integrated Services Routers (ISR 900), a fixed-configuration router line for small offices, branches and remote sites. It runs Cisco IOS Software (Release 15.8(3)M and later), so it uses the same command line, routing and security feature set familiar from larger Cisco ISRs.
Two Gigabit WAN ports, four Gigabit LAN ports
The C921-4P has two Gigabit Ethernet WAN ports for a primary and backup internet or carrier link, plus a 4-port Gigabit Ethernet managed switch for local devices. Cisco lists an RJ-45 console port and a USB 2.0 Type A port.
Security features with the Security licence
With the Security technology package, the router adds zone-based policy firewall, IPsec VPN, DMVPN, FlexVPN and GET VPN, with hardware-accelerated DES, 3DES and AES (128/192/256) encryption. Cisco lists support for 50 IPsec tunnels and quotes up to 250 Mbps IPsec performance for the Security licence in the 900 Series datasheet.
Standard routing protocols
OSPF, BGP, EIGRP and RIPv1/v2 are supported, alongside SNMPv3 and SSH management, so the C921-4P can join an existing Cisco-routed WAN or VPN design.
Internal power supply
Unlike the VDSL models in the 900 Series, the C921-4P has an internal 100-240 VAC power supply, so there is no external power brick to secure in the cabinet.
Cisco C921-4P Datasheet — Technical Specifications
Interfaces
| WAN | 2 x Gigabit Ethernet |
| LAN | 4-port Gigabit Ethernet managed switch |
| Console | RJ-45 |
| USB | 1 x USB 2.0 Type A |
Software & Memory
| Operating system | Cisco IOS Software, Release 15.8(3)M and later |
| DRAM | 1 GB (default) |
| Flash | 2 GB (not upgradable) |
| Technology packages | IP Base (default), Application Experience (APP), Security (SEC / SEC-NPE) |
Security & VPN
| Firewall | Zone-based policy firewall (Security licence) |
| VPN | IPsec VPN, DMVPN, FlexVPN, GET VPN (Security licence) |
| Encryption | Hardware-accelerated DES, 3DES, AES 128, AES 192, AES 256 |
| IPsec tunnels | 50 |
| IPsec performance | Up to 250 Mbps (Security licence, per 900 Series datasheet) |
Routing & Management
| Routing protocols | OSPF, BGP, EIGRP, RIPv1/v2 |
| Management | SNMPv3, SSH, CLI, web interface |
Power & Physical
| Power supply | Internal, 100-240 VAC, 50-60 Hz |
| Dimensions (H x W x D) | 1.70 x 9.0 x 9.5 in. |
| Weight | 2.65 lb maximum |
| Operating temperature | 0° to 50°C (with altitude de-rating) |
| Operating humidity | 5% to 95% non-condensing |
| Mounting kits | ACS-900-RM-19 (rack) and ACS-900-DM (under-desk), sold separately |
Compatibility & Software Support
Software
The C921-4P runs classic Cisco IOS (not IOS XE). Features available depend on the technology package licences on the unit: IP Base is the default, with Application Experience and Security packages adding application and security features.
End-of-Sale notice
Cisco has published the "End-of-Sale and End-of-Life Announcement for the Cisco ISR 900 Series Routers, Licenses and Accessories" (announced 28 July 2025), which covers the C921-4P. Milestones: End-of-Sale 28 July 2026; Last Ship Date 27 October 2026; End of SW Maintenance Releases 28 July 2027; End of Vulnerability/Security Support 27 July 2029; Last Date of Support 31 July 2031. Cisco names the C1121-4P (ISR 1100 4P Dual GE SFP Router) as the replacement product.
Warranty
Local Singapore unit with local warranty. For warranty claims, keep your SourceIT invoice as proof of purchase.
Package Contents & Cisco Branch Router Ordering Information
What the Part Number Covers
C921-4P is the router with internal power supply. The Cisco datasheet does not publish an in-the-box list; rack-mount (ACS-900-RM-19) and under-desk (ACS-900-DM) kits are separate accessories.
Cisco Branch Router Family
| Model | Key difference |
| C921-4P (this listing) | 2 x GE WAN, 4-port GE LAN, internal power supply |
| C931-4P | 2 x GE WAN, 4-port GE LAN, internal power supply (900 Series) |
| C927-4P / C926-4P / C927-4PM | 1 x GE + 1 x VDSL WAN (Annex A, B/J or M), external power adapter |
| C921-4PLTE variants | C921 with integrated LTE WAN |
| Cisco ISR 1100 C1111-4P | IOS XE, dual GE WAN (one GE/SFP combo), 4-port GE LAN, SD-WAN capable; also end-of-sale |
| C1121-4P | Cisco-named replacement for C921-4P (ISR 1100 4P Dual GE SFP Router) |
Datasheet & Downloads
Frequently Asked Questions — Cisco C921-4P
How many WAN ports does the C921-4P have?
Two Gigabit Ethernet WAN ports, plus a separate 4-port Gigabit Ethernet LAN switch.
Does it support site-to-site VPN?
Yes, with the Security technology package: IPsec VPN, DMVPN, FlexVPN and GET VPN, with up to 50 IPsec tunnels.
Does it need an external power adapter?
No. The C921-4P has an internal 100-240 VAC power supply.
Is the C921-4P end-of-sale?
Yes. Cisco's end-of-sale date was 28 July 2026 and the last ship date is 27 October 2026. Security fixes continue until 27 July 2029 and support ends 31 July 2031. Cisco's named replacement is the C1121-4P.
Does it run IOS XE or SD-WAN?
No. The C921-4P runs Cisco IOS Software. For IOS XE and SD-WAN, Cisco positions the ISR 1100 series, including the replacement C1121-4P.
