Cisco Router ISR 900 Series C921-4P Overview
Cisco Router ISR 900 Series C921-4P is a genuine edge and wide-area routing product from Cisco, a leading enterprise networking vendor whose Catalyst, Nexus and ISR families power campus, data-center and branch networks worldwide. Belonging to the Cisco Router ISR 900 Series family, the C921-4P unit is built to the original factory specification, so it integrates with existing Cisco deployments predictably and behaves exactly as the platform documentation describes. In the network, it is deployed as a standalone unit or as part of a larger managed network, following the standard operating procedures of the platform.
From a specification standpoint, it offers 2 ports for client, server or uplink connectivity. These are the original factory figures for this model, giving administrators a clear picture of what the unit can deliver before it enters service. Standard mounting, cabling and management practices apply, so deployment follows the same procedures as other Cisco hardware already running in the environment.
Typical deployments include branch and campus WAN connectivity, service-provider edge and MPLS deployments, and secure remote-site interconnect. Organizations commonly source it for refresh programs, capacity expansion and spares management, keeping a tested unit on hand so outages stay short and replacements are predictable. The factory detail for this unit reads: “Features a robust internal power supply, ideal for high-security Ethernet networks.”. This makes it a practical choice when original-spec hardware is required at a predictable cost.
Every unit at LinkNewNet is inspected and tested before dispatch, and stock is graded, cleaned and verified for correct operation, including port status, console access and firmware state. Our warranty coverage and responsive technical support protect the purchase after it arrives, and our team can confirm revision levels and software compatibility before you order. For volume requirements we also offer configuration checks and staged delivery options.
Contact our sales team for current availability, lead time and shipping options for the C921-4P. We respond quickly with stock status and a firm quote, so you can plan the refresh or expansion with confidence.
Key Specifications
Applications
Enterprise WAN
Branch and campus routing with advanced services.
Service Provider
Edge routing for ISP and MPLS deployments.
Data Center
Interconnect core and aggregation layers reliably.
Buying a Pre-Owned C921-4P
Verify the unit is tested, firmware confirmed, and condition documented. Every unit is fully tested and warranty covered. Contact our team for current stock and availability.
C921-4P Specification | |
WAN interfaces | 2 ports Gigabit Ethernet (GE) |
LAN interfaces | 4-port GE managed switch |
Integrated USB 2.0 | Yes |
Maximum crypto throughput (bit-rate policed) | 150 Mbps |
Cisco IOS Software | |
IP and IP services | ● Routing Information Protocol Versions 1 and 2 (RIPv1 and RIPv2) ● Generic Routing Encapsulation (GRE) and Multipoint GRE (MGRE) ● Cisco Express Forwarding ● Standard 802.1d Spanning Tree Protocol ● Layer 2 Tunneling Protocol (L2TP) ● L2TP Version 3 (L2TPv3) ● Network Address Translation (NAT) ● Dynamic Host Configuration Protocol (DHCP) server, relay, and client ● Dynamic DNS ● DNS Proxy ● DNS Spoofing ● Access Control Lists (ACLs) ● IPv4 and IPv6 multicast ● Open Shortest Path First (OSPF) ● Border Gateway Protocol (BGP) ● Performance Routing (PfR) ● Enhanced Interior Gateway Routing Protocol (EIGRP) ● Virtual Route Forwarding (VRF) Lite ● Next Hop Resolution Protocol (NHRP) ● Bidirectional Forwarding Detection (BFD) ● Web Cache Communication Protocol (WCCP) |
Switch features | ● Auto Media Device In/Media Device Cross Over (MDI-MDX) ● 25 802.1Q VLANs ● MAC filtering ● Switched Port Analyzer (SPAN) ● Storm control ● Smart ports ● Secure MAC address ● Internet Group Management Protocol Version 3 (IGMPv3) snooping ● 802.1X |
Security features | Secure connectivity: ● Secure Sockets Layer (SSL) VPN for secure remote access ● Hardware-accelerated DES, 3DES, AES 128, AES 192, and AES 256 ● Public-Key-Infrastructure (PKI) support ● 50 IPsec tunnels ● Cisco Easy VPN client and server ● NAT transparency ● Dynamic Multipoint VPN (DMVPN) ● Tunnel-less Group Encrypted Transport VPN (GET VPN) ● VRF-aware IPsec ● IPsec over IPv6 ● Adaptive control technology ● Session Initiation Protocol (SIP) application-layer gateway ● Cisco IOS Firewall: ◦ Zone-based policy firewall ◦ VRF-aware stateful inspection routing firewall ◦ Stateful inspection transparent firewall ● Advanced application inspection and control ● HTTPS, FTP, and Telnet Authentication Proxy ● Dynamic and static port security ● Firewall stateful failover ● VRF-aware firewall ● Cisco IOS Software black and white lists ● Integrated threat control: ◦ Intrusion Prevention System (IPS) ● Control plane policing ● Flexible packet matching ● Network foundation protection |
Quality of Service (QoS) | ● Low-Latency Queuing (LLQ) ● Weighted Fair Queuing (WFQ) ● Class-Based WFQ (CBWFQ) ● Class-Based Traffic Shaping (CBTS) ● Class-Based Traffic Policing (CBTP) ● Policy-Based Routing (PBR) ● Class-Based QoS MIB ● Class of Service (CoS)-to-Differentiated Services Code Point (DSCP) mapping ● Class-Based Weighted Random Early Detection (CBWRED) ● Network-Based Application Recognition (NBAR) ● Link Fragmentation and Interleaving (LFI) ● Resource Reservation Protocol (RSVP) ● Real-Time Transport Protocol (RTP) header compression (cRTP) ● Differentiated Services (DiffServ) ● QoS preclassify and prefragmentation ● Hierarchical QoS (HQoS) |
Management | ● Cisco Configuration Professional ● Cisco Configuration Express ● Cisco Configuration Engine support ● Cisco AutoInstall ● Cisco IP Service-Level Agreement (IP SLA) ● Cisco IOS Embedded Event Manager (EEM) ● CiscoWorks ● Cisco Security Manager ● Telnet, Simple Network Management Protocol Version 3 (SNMPv3), Secure Shell (SSH) Protocol, Command-Line Interface (CLI), and HTTP management ● RADIUS and TACACS+ ● Cisco Next Generation Plug-and-Play (NG PnP) Protocol |
Number of recommended users | ● 50 |
Default and maximum DRAM | ● Default 1 GB |
Default and maximum flash memory | ● 2 GB on all Cisco 900 Series ISR models; not upgradable |
WAN | ● Refer to Table 2 for details |
LAN switch | ● Refer to Table 2 for details |
Separate console ports | ● RJ-45 |
USB 2.0 | ● One USB 2.0 Type A port |
Physical dimensions | H x W x D = 1.70 x 9.0 x 9.5 in. (4.32 x 22.86 x 24.13 cm) (includes rubber feet) |
Power supply | Power specifications: ● AC input voltage: Universal 100 to 240 VAC ● Frequency: 50 to 60 Hz ● Internal power supply (C921-4P and C931-4P only) |
C921-4P - Product Notes
This listing is a specific SKU variant of the C921-4P family. Review the specifications above and confirm compatibility with your existing infrastructure, including software version, mounting, and interface requirements, before ordering.
For volume requirements we offer configuration checks and staged delivery options. Our team can confirm revision levels, software compatibility, and lead time before you place an order.
Every unit at LinkNewNet is inspected and tested before dispatch, and stock is graded, cleaned and verified for correct operation.
C921-4P - Product Notes
This listing is a specific SKU variant of the C921-4P family. Review the specifications above and confirm compatibility with your existing infrastructure, including software version, mounting, and interface requirements, before ordering.
For volume requirements we offer configuration checks and staged delivery options. Our team can confirm revision levels, software compatibility, and lead time before you place an order.
Every unit at LinkNewNet is inspected and tested before dispatch, and stock is graded, cleaned and verified for correct operation.
C921-4P - Cisco Series Notes
This listing is part of the Cisco enterprise networking product family, sourced and tested by LinkNewNet for enterprise deployment. Cisco router is positioned at the WAN edge, branch, or service-provider aggregation point. It provides routing, VPN, QoS and security services, and integrates with Cisco IOS-XE / IOS-XR management.
Deployment guidance: When planning this C921-4P unit into a network, confirm the software image (IOS/IOS-XE/NX-OS) required, the power and cooling profile, and the upstream/downstream interface types that match your existing infrastructure. For a like-for-like refresh, match the feature set of the units already in service so management and automation behave consistently.
Our Cisco reconditioning process: Every pre-owned Cisco unit at LinkNewNet passes a documented reconditioning flow before dispatch - visual inspection, internal cleaning, firmware verification, port-by-port testing, and configuration reset to factory defaults. This ensures the unit you receive operates reliably and integrates cleanly with your existing Cisco management tools.
Related models in this family: C927-4P, C921-4PLTEAS, C921J-4P, C927-4PM, C941J-4P. Compare specifications to confirm the right port density, feature set and uplink options for your deployment.
Model code: P = PoE (Power over Ethernet) support - this suffix indicates the feature set, power, or regulatory variant of the C921-4P, which affects software licensing and regional compliance.
