Cisco 1921 vs ISR4221
The ISR 4221 is the modern IOS XE replacement for the end-of-life Cisco 1921 (ISR G2), bringing far more memory, higher licensed throughput, and Cisco SD-WAN support. Any 1921 still in production should be migrated to the ISR 4221.
Cisco 1921 ISR G2
Entry ISR Generation 2 branch router with two GE ports and EHWIC slots running classic IOS 15.
- 2 onboard GE ports, 2 EHWIC slots
- 512 MB DRAM / 256 MB flash default (classic IOS 15)
- No native IOS XE or Cisco SD-WAN
- End-of-life; last day of support reached for the platform
Cisco ISR 4221
Entry ISR 4000 branch router on IOS XE with NIM slots, more memory, and SD-WAN support.
- 2 onboard GE ports, 2 NIM slots
- 4 GB DRAM / 8 GB flash default
- Up to ~300 Mbps aggregate throughput (license)
- Cisco IOS XE with Cisco SD-WAN support
Cisco 1921 ISR G2 vs Cisco ISR 4221: spec comparison
| Spec | Cisco 1921 ISR G2 | Cisco ISR 4221 |
|---|---|---|
| Onboard GE ports | 2 | 2 |
| Modular slots | 2 EHWIC | 2 NIM |
| Aggregate throughput | Tens of Mbps class (G2) | 100 to 300 Mbps (license) |
| Default DRAM | 512 MB | 4 GB |
| Default flash | 256 MB CF | 8 GB |
| Software | Cisco IOS 15 (classic) | Cisco IOS XE |
| Native SD-WAN | No | Yes (Cisco SD-WAN) |
| Voice / DSP | PVDM3 (classic) | PVDM4 via NIM |
| Lifecycle status | End-of-life | Mature but supported |
Choose Cisco 1921 ISR G2 if
Choose the 1921 only to keep an existing low-bandwidth site running on EHWIC modules you already own until a planned refresh; it has no advantage for new purchases.
Choose Cisco ISR 4221 if
Choose the ISR 4221 for any refresh: 8x the DRAM, IOS XE, NIM modularity, higher licensed throughput, and Cisco SD-WAN support.
Verdict
Migrate from the Cisco 1921 to the ISR 4221. The 1921 is end-of-life on classic IOS with minimal memory, while the 4221 brings IOS XE, much more memory and flash, higher throughput, and SD-WAN. Keep a 1921 only briefly where EHWIC modules and low bandwidth make immediate replacement uneconomical.
Frequently asked questions
What is the replacement for the Cisco 1921?
The Cisco ISR 4221 is the modern replacement for the 1921, moving from classic IOS 15 and EHWIC slots to IOS XE, NIM modules, more memory, and Cisco SD-WAN support.
Does the ISR 4221 use the same modules as the 1921?
No. The 1921 uses EHWIC modules while the ISR 4221 uses NIM modules, so interface cards generally must be repurchased when migrating.
Is the Cisco 1921 end of life?
Yes. The 1921 reached end-of-sale in 2018 and has passed its last day of support, so it should be replaced to keep a supported, patched software image.
How much throughput does the ISR 4221 provide?
The ISR 4221 supports roughly 100 to 300 Mbps of aggregate throughput depending on the performance license, well above the practical capability of the older 1921.
More ISR G comparisons
Specs are for planning and may change; Uniqcli confirms the current Cisco bill of materials and pricing on your quote. Cisco, Catalyst, Nexus, Meraki, and Firepower are trademarks of Cisco Systems, Inc.; Uniqcli LLC is an independent authorized Cisco partner.