Cisco 3945 vs ISR 4451-X
The Cisco 3945 (CISCO3945/K9) is an end-of-life ISR G2 flagship; the ISR 4451-X (ISR4451-X/K9) is its modern replacement, scaling from 1 Gbps to 2 Gbps of licensed throughput with multicore IOS XE and SD-WAN. For a refresh, move to the ISR 4451-X.
Cisco 3945 Integrated Services Router
End-of-life ISR G2 top-of-line branch router on classic IOS, now past last day of support.
- 3 onboard 10/100/1000 RJ-45 ports
- 4 EHWIC, 4 SM (with SM double-wide), 3 PVDM3, 1 ISM
- Classic Cisco IOS 15.x on a single services CPU
- End of sale and end of support; no further fixes
Cisco ISR 4451-X
Current top-of-line branch / aggregation router with multicore IOS XE and 1 Gbps to 2 Gbps licensed throughput.
- 4 onboard GE ports (combo RJ-45 / SFP)
- 3 NIM slots and 2 SM-X slots for modular services
- 1 Gbps default, upgradable to 2 Gbps via boost license
- IOS XE with Cisco SD-WAN; TAA-compliant options
Cisco 3945 Integrated Services Router vs Cisco ISR 4451-X: spec comparison
| Spec | Cisco 3945 Integrated Services Router | Cisco ISR 4451-X |
|---|---|---|
| Status | End of sale / end of support | Current shipping product |
| Onboard GE ports | 3 x 10/100/1000 RJ-45 | 4 x GE (RJ-45 / SFP combo) |
| Default throughput | Up to ~150-350 Mbps (services on) | 1 Gbps, upgradable to 2 Gbps |
| Modular slots | 4 EHWIC, 4 SM, 3 PVDM3, 1 ISM | 3 NIM, 2 SM-X, 1 PVDM4 (ISC) |
| Software | Classic Cisco IOS 15.x | Cisco IOS XE |
| Control / data plane | Single shared CPU | Separate multicore control and data planes |
| SD-WAN support | No | Yes (Cisco SD-WAN / vManage) |
| Default DRAM / flash | 1 GB DRAM / 256 MB CF | 4 GB DRAM / 8 GB flash (default) |
| Redundant power | Optional internal RPS | Dual internal power supplies supported |
| Rack height | 3RU | 2RU |
| TAA / federal | Legacy, no current TAA SKU | TAA-compliant options, GPC-payable |
Choose Cisco 3945 Integrated Services Router if
Retain the 3945 only to preserve a specific legacy SM or PVDM3 investment during a phased transition. It has no support coverage and should not anchor a new design.
Choose Cisco ISR 4451-X if
Choose the ISR 4451-X for the most demanding branch and regional aggregation roles needing 1 Gbps to 2 Gbps, modular SM-X services, and SD-WAN on supported IOS XE.
Verdict
Migrate from the 3945 to the ISR 4451-X. The 4451-X delivers 1 Gbps to 2 Gbps of dedicated data-plane throughput, modern IOS XE with SD-WAN, and SM-X modularity in 2RU. Hold the 3945 only briefly to protect a legacy module during cutover.
Frequently asked questions
Is the Cisco 3945 still supported by Cisco?
No. The CISCO3945/K9 has reached end of sale and end of support, so it receives no further software maintenance or security fixes. The recommended replacement is the ISR 4451-X.
What is the modern equivalent of the Cisco 3945?
The ISR 4451-X (ISR4451-X/K9) is the top-of-line ISR 4000 router and the direct successor to the 3945, with 1 Gbps to 2 Gbps licensed throughput and IOS XE.
Can the ISR 4451-X reuse my 3945 service modules?
No. The 4451-X uses NIM and SM-X modules and PVDM4, not the EHWIC/SM/PVDM3 hardware from the 3945, so plan for new modules during migration.
Is the ISR 4451-X available TAA-compliant for federal buyers?
Yes. The ISR 4451-X is offered with TAA-compliant options suitable for US federal procurement, and is GPC-payable through an authorized partner.
More ISR G comparisons
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