Cisco C921-4P ISR 921 Gigabit Ethernet Security Router

A fixed-configuration branch router from the Cisco 900 Series Integrated Services Routers, which Cisco aims at small branch offices and managed customer-premises deployments. It has two Gigabit Ethernet WAN ports for failover or load balancing, a four-port Gigabit Ethernet managed switch for the LAN, an RJ-45 console port and a USB 2.0 port. It has an internal power supply on 100 to 240 VAC, whereas several other 900 models use an external adapter.

Cisco recommends it for up to 50 users. It has 1 GB of DRAM and 2 GB of flash, and neither is upgradable. It runs the Cisco IOS Universal image, release 15.8(3)M or later.

Features depend on the licence: IP Base is the default; Application Experience (SL-900-APP) adds MPLS, NBAR2 and PfRv3; and Security (SL-900-SEC) adds zone-based firewall, IPsec, DMVPN and FlexVPN, with up to 250 Mbps of IPsec throughput. A non-payload-encryption version of the security licence also exists. Cisco lists up to 50 IPsec tunnels.

The chassis is 1.70 x 9.0 x 9.5 in, weighs up to 2.65 lb (1.20 kg) and is rated 0 to 50°C. The C921-4PLTE models add a CAT4 LTE modem, and the C931-4P has the same port layout.

Lifecycle: Cisco announced end of life on July 28, 2025. End of sale was July 28, 2026, the last ship date is October 27, 2026, software maintenance ends July 28, 2027 and the last date of support is July 31, 2031. Cisco names the ISR 1100 C1121-4P as the replacement.

To confirm fit, check which licence the unit carries, since it decides whether VPN and firewall features will run.

More from this family: Cisco Router.

Related parts: C1121-4P.