Cisco 2951 vs ISR 4351
The Cisco 2951 (CISCO2951/K9) is an end-of-life ISR G2; its modern replacement is the ISR 4351 (ISR4351/K9), which delivers roughly 4x the routing throughput, multicore services on a separate plane, and current IOS XE software. For any new or refresh deployment, migrate to the ISR 4351.
Cisco 2951 Integrated Services Router
End-of-life ISR G2 mid-range branch router running classic IOS, now past last day of support.
- 3 onboard 10/100/1000 RJ-45 ports
- 4 EHWIC slots, 2 SM slots, 3 onboard DSP (PVDM3) slots
- Runs classic Cisco IOS 15.x, not IOS XE
- End of sale and end of support; no further software or security fixes
Cisco ISR 4351
Current mid-range branch router with multicore IOS XE, software-defined performance, and SD-WAN readiness.
- 3 onboard GE (RJ-45 / SFP combo) WAN/LAN ports
- 3 NIM slots and 2 SM-X slots for modular services
- 200 Mbps default throughput, upgradable to 400 Mbps via license
- IOS XE with Cisco SD-WAN and TAA-compliant options for federal
Cisco 2951 Integrated Services Router vs Cisco ISR 4351: spec comparison
| Spec | Cisco 2951 Integrated Services Router | Cisco ISR 4351 |
|---|---|---|
| Status | End of sale / end of support | Current shipping product |
| Onboard GE ports | 3 x 10/100/1000 RJ-45 | 3 x GE (RJ-45 and SFP) |
| Default IP throughput | Up to ~75-100 Mbps (services on) | 200 Mbps, upgradable to 400 Mbps |
| Modular slots | 4 EHWIC, 2 SM, 3 PVDM3 | 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 (Viptela/IOS XE SD-WAN not supported) | Yes (Cisco SD-WAN / vManage) |
| Default DRAM / flash | 512 MB DRAM / 256 MB CF | 4 GB DRAM / 4 GB flash (default) |
| Onboard services | Hardware crypto, voice/DSP via PVDM3 | Hardware crypto, app hosting (KVM container), PVDM4 |
| Rack height | 2RU | 1RU |
| TAA / federal | Legacy, no current TAA SKU | TAA-compliant options, GPC-payable |
Choose Cisco 2951 Integrated Services Router if
Only keep the 2951 if you have a short-term need to preserve a specific legacy EHWIC/PVDM3 module or IOS feature during a phased cutover. It receives no further support, so it should not anchor any new design.
Choose Cisco ISR 4351 if
Choose the ISR 4351 for any new branch, lifecycle refresh, or SD-WAN initiative. It offers far higher throughput, modern IOS XE, app hosting, and a supported lifecycle.
Verdict
Migrate from the 2951 to the ISR 4351. The 4351 roughly quadruples usable throughput, moves you to supported IOS XE with SD-WAN, and consolidates into 1RU. The only reason to delay is preserving a legacy module short-term during a phased cutover.
Frequently asked questions
Is the Cisco 2951 still supported?
No. The CISCO2951/K9 has passed end of sale and end of support, so it no longer receives software maintenance, bug fixes, or security patches. Plan a refresh to a supported platform such as the ISR 4351.
What is the direct replacement for the Cisco 2951?
The ISR 4351 (ISR4351/K9) is the closest modern equivalent in the Cisco 4000 family, matching the 2951's mid-range branch role with much higher performance and IOS XE software.
Will my 2951 EHWIC and PVDM3 modules work in the ISR 4351?
No. The 4351 uses NIM and SM-X modules plus PVDM4, not the EHWIC/SM/PVDM3 modules from the 2951. You should plan for new modules as part of the migration.
Does the ISR 4351 support Cisco SD-WAN?
Yes. The ISR 4351 runs IOS XE and is supported on Cisco SD-WAN (vManage), which the legacy 2951 cannot do.
More ISR G comparisons
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