ISR 4000 Series (ISR 4321 / 4331 / 4351) support dates
| Milestone | Date | Basis | Source |
|---|---|---|---|
| End-of-Life Announcement Date | 7 November 2022 | Vendor-publishedOne bulletin, with a single milestone table, covers the 4321, 4331 and 4351. | Cisco EOL14896 (Amended, updated 6 Nov 2024): End-of-Sale and End-of-Life Announcement for the Cisco ISR4200, ISR4300 and select ISR4400 Series Platform |
| End-of-Sale Date (HW, License) | 7 November 2023 | Vendor-publishedThe 4321, 4331 and 4351 support pages also show End-of-Sale Date 07-NOV-2023. | Cisco EOL14896 (Amended) |
| Last Ship Date (HW, License) | 6 February 2024 | Vendor-published | Cisco EOL14896 (Amended) |
| End of Routine Failure Analysis Date | 6 November 2024 | Vendor-published | Cisco EOL14896 (Amended) |
| End of New Service Attachment Date | 6 November 2024 | Vendor-published | Cisco EOL14896 (Amended) |
| End of SW Maintenance Releases Date | 31 August 2025 | Vendor-published | Cisco EOL14896 (Amended) |
| End of Service Contract Renewal Date | 5 February 2028 | Vendor-published | Cisco EOL14896 (Amended) |
| End of Vulnerability/Security Support | 30 November 2028 | Vendor-publishedThe bulletin adds that standard EoVSS support for the IOS XE 17.12 train runs until September 2027. After that, 'necessary ad-hoc EoVSS maintenance releases' will be made available for ISR 4K until November 2028. | Cisco EOL14896 (Amended) |
| Last Date of Support | 30 November 2028 | Vendor-publishedCisco's 4321, 4331 and 4351 support pages each show End-of-Support Date 30-NOV-2028. | Cisco EOL14896 (Amended) |
| Last Date of Support (Brazil SKUs ISR4321BR/K9, ISR4331BR/K9) | 31 January 2029 | Vendor-publishedApplies only to the two Brazil-specific PIDs on their own bulletin: End-of-Sale 26 Jan 2024, End of SW Maintenance 31 Aug 2025, Last Date of Support 31 Jan 2029, and no replacement available. It does not apply to UK-market ISR4321/K9 or ISR4331/K9 units. | Cisco EOL15204 (updated 27 Oct 2023): End-of-Sale and End-of-Life Announcement for the Cisco ISR4200 and ISR4300 Series Platform for Brazil |
Where the ISR 4000 Series (ISR 4321 / 4331 / 4351) stands today
One Cisco bulletin, the amended EOL14896 (updated 6 November 2024), gives a single milestone table to all three routers, their -AX, -AXV, -SEC, -V, -VSEC, -DNA and -PM20 variants and the ISR 4331-DC. Already past are End-of-Sale for hardware and licences on 7 November 2023, End of New Service Attachment on 6 November 2024 and End of SW Maintenance Releases on 31 August 2025. Still ahead are End of Service Contract Renewal on 5 February 2028 and End of Vulnerability/Security Support with the Last Date of Support on 30 November 2028. Cisco's 4000 Family data sheet, updated 23 June 2026, still says 'The Cisco ISR 4000 Family is orderable and shipping', but for these three models the bulletin's End-of-Sale date is the authoritative status, and each model's support page shows 'End of Sale'.
Dates are per product ID: run 'show inventory', read the chassis PID (ISR4331/K9 or ISR4321-SEC/K9, for example) and find it in Table 2 of EOL14896. The Brazil-market ISR4321BR/K9 and ISR4331BR/K9 follow a separate bulletin, EOL15204, with End-of-Sale on 26 January 2024, a Last Date of Support of 31 January 2029 and no replacement; those dates do not apply to UK-market ISR4321/K9 or ISR4331/K9 units.
Dates are per product ID. Run 'show inventory' to read the chassis PID (for example ISR4331/K9 or ISR4321-SEC/K9) and find it in Table 2 of EOL14896 (https://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integrated-services-routers-isr/select-isr4k-series-platform-eol.html). The Brazil-market PIDs ISR4321BR/K9 and ISR4331BR/K9 are instead on EOL15204 (https://www.cisco.com/c/en/us/products/collateral/routers/4000-series-integrated-services-routers-isr/isr-4200-4300-platform-brazil-eol.html), with a 31 Jan 2029 Last Date of Support. Contract coverage for a specific serial number is a separate entitlement check with your Cisco partner.
What still works after Cisco support ends
The last supported IOS XE trains for these routers are 17.9.x and 17.12.x; 17.10.x and 17.11.x are not supported. Standard End of Vulnerability/Security Support for 17.12 runs until September 2027, after which the bulletin says 'necessary ad-hoc EoVSS maintenance releases' will be made available for ISR 4K until November 2028. For SD-WAN, it says vManage releases 20.12, 20.15 and 20.18 will support the 17.12.x train. After 30 November 2028, PSIRT will still accept reports on these routers but will analyse, fix and disclose none of them, nor issue CVEs.
An uncovered ISR 4321, 4331 or 4351 cannot be added to a new Cisco contract, since End of New Service Attachment passed on 6 November 2024; an existing contract can be renewed until 5 February 2028 but cannot run beyond 30 November 2028. The bulletin also lists Cisco Certified Refurbished Equipment that may be on offer in some countries, in limited quantities, until the Last Date of Support, and Technology Migration Program trade-in credit, where eligible, through a Cisco partner or account team.
- IOS XE software maintenance (bug-fix) releases for these platforms ended on 31 Aug 2025. Standard End of Vulnerability/Security Support for the IOS XE 17.12 train on these routers runs until September 2027. After that, the bulletin says 'necessary ad-hoc EoVSS maintenance releases' will be made available for ISR 4K until November 2028, with the formal EoVSS and Last Date of Support on 30 Nov 2028. (cisco.com)
- The last supported IOS XE release trains for these ISR 4000 platforms are 17.9.x and 17.12.x. Trains 17.10.x and 17.11.x are not supported. For SD-WAN, the bulletin says future vManage releases 20.12, 20.15 and 20.18 will support the 17.12.x train. (cisco.com)
- Cisco may offer free software updates for high-severity security problems as a special customer service. It decides case by case, and such updates are typically limited to Critical and High severity. Where Cisco has offered one, eligible noncontract customers may get it by contacting Cisco TAC, with the URL of the Cisco document offering the update. Free updates do not entitle the customer to new licences, feature sets or major upgrades. (sec.cloudapps.cisco.com)
- After the Last Day of Support (30 Nov 2028), Cisco PSIRT will accept vulnerability reports for these routers but will not analyse, fix or disclose them, or issue CVEs for them. (sec.cloudapps.cisco.com)
Vendor support you can still buy
- Renewal of an existing Cisco service contract — Available until 5 Feb 2028. A renewed contract cannot run past the Last Date of Support (30 Nov 2028). (cisco.com)
- Cisco Certified Refurbished Equipment — The bulletin says refurbished units may be available in limited supply in certain countries, first come first served, until the Last Date of Support. (cisco.com)
- Cisco Technology Migration Program (TMP) — Trade-in credit towards new Cisco equipment where eligible, arranged through a Cisco partner or account team. (cisco.com)
What a maintenance contract needs to cover on the ISR 4000 Series (ISR 4321 / 4331 / 4351)
The three routers differ enough that a contract should name the exact model. The ISR 4321 and 4331 are 1RU and the 4351 is 2RU, each with a 19-inch rack-mount kit. In 4321, 4331 and 4351 order, the data sheet gives 2, 3 and 3 onboard 10/100/1000 WAN/LAN ports (2, 2 and 3 RJ-45-based; 1, 2 and 3 SFP-based), 2, 2 and 3 NIM slots, 0, 1 and 2 SM-X slots, and one onboard ISC slot each, and every installed module belongs on the contract. DDR3 ECC memory and flash both start at 4 GB, with ceilings of 8 GB on the 4321 and 16 GB on the 4331 and 4351.
The 4321 uses an external AC or PoE supply, the 4331 an internal AC or PoE supply (DC only on the 4331-DC) and the 4351 an internal AC, DC or PoE supply, and the data sheet lists no redundant supply option for any of them, so supply replacement should be clearly defined. Field Notice FN74073 (15 May 2024) says some PWR-4320-AC supplies, which it applies to the ISR 4321, may fail early because of a capacitor processing issue, with affected units found by serial number and replaced through RMA. The optional PoE supply feeds up to 120 W, 250 W or 500 W to endpoints on the 4321, 4331 and 4351 respectively, via optional integrated switch modules; the 4331-DC has no PoE. Network third-party maintenance generally provides fault diagnosis, parts and engineer call-outs for routers like these, and the maintenance coverage builder accepts quote requests.
| Specification | Detail | Source |
|---|---|---|
| Form factor | ISR 4321: 1RU. ISR 4331: 1RU. ISR 4351: 2RU. A 19in rack-mount kit is included with all three. | cisco.com |
| Onboard ports | Total onboard 10/100/1000 WAN/LAN ports: 4321 has 2, 4331 has 3, 4351 has 3. RJ-45-based: 2 / 2 / 3. SFP-based: 1 / 2 / 3. | cisco.com |
| Module slots | NIM slots: 2 / 2 / 3. Enhanced service-module (SM-X) slots: 0 / 1 / 2. Each model also has 1 onboard ISC slot (order: 4321 / 4331 / 4351). | cisco.com |
| Memory and flash | DDR3 ECC DRAM: 4 GB default on all three, maximum 8 GB (4321) or 16 GB (4331, 4351). Flash: 4 GB default, maximum 8 GB (4321) or 16 GB (4331, 4351). | cisco.com |
| Aggregate throughput | Default: 50 / 100 / 200 Mbps. With performance licence: 100 / 300 / 400 Mbps (order: 4321 / 4331 / 4351). | cisco.com |
| Power supplies | 4321: external AC or PoE supply. 4331: internal AC or PoE, with DC only on the 4331-DC. 4351: internal AC, DC or PoE. The data sheet lists no redundant power supply option for any of the three. | cisco.com |
| PoE budget | Maximum endpoint PoE from the optional PoE power supply: 4321 120 W, 4331 250 W, 4351 500 W. Platform-only maximum power with the PoE supply: 260 W / 530 W / 990 W. PoE is not supported on the 4331-DC. Inline power (802.3af PoE or 802.3at PoE+) goes to optional integrated switch modules. | cisco.com |
Extend or refresh the ISR 4000 Series (ISR 4321 / 4331 / 4351)?
Extending an ISR 4321, 4331 or 4351 is reasonable where the router is stable on 17.9.x or 17.12.x and its throughput is enough: 50, 100 and 200 Mbps aggregate by default, or 100, 300 and 400 Mbps with the performance licence, respectively. First, though, check Field Notice FN64253: revision 10.3 (7 May 2025) lists the ISR4321/K9, ISR4331/K9 and ISR4351/K9 as routers that 'might fail after 18 months or longer in operation due to a clock signal component failure', after which the system 'will not boot, and is not recoverable'. Cisco's remedy is a TAC replacement, and a TAC case needs a valid support contract or a unit under warranty; Cisco Support Assistant can check whether a serial number is affected.
Refresh becomes the better choice when a router needs a non-security IOS XE bug fix, which ended with software maintenance on 31 August 2025, or when a site's link outgrows the licensed throughput above. Cisco names the replacements in EOL14896: ISR4321 and ISR4331 PIDs map to the Catalyst 8200 Edge C8200-1N-4T, and ISR4351 PIDs to the Catalyst 8300 Edge C8300-2N2S-6T. The ISR4331-DC/K9 and the -PM20 SKUs have no listed replacement, so sites using them need a separate plan.
- Field Notice FN64253 (revision 10.3, 7 May 2025) lists the ISR4321/K9, ISR4331/K9 and ISR4351/K9 as affected. These routers 'might fail after 18 months or longer in operation due to a clock signal component failure', after which the system 'will not boot, and is not recoverable'. Cisco tells affected customers to contact TAC for a replacement unit, and opening a TAC case needs a valid support contract or a product under warranty. Cisco Support Assistant (CSA) can check whether a serial number is affected. (cisco.com)
- Field Notice FN74073 (15 May 2024): some PWR-4320-AC power supplies, which the notice applies to the ISR 4321, may fail early because of a capacitor processing issue. Affected units are identified by serial-number check and replaced through the RMA process. (cisco.com)
- Software maintenance ended on 31 Aug 2025, so new non-security IOS XE bug fixes for these routers have stopped. Plan on staying within the 17.9.x or 17.12.x trains. Standard security support for 17.12 runs only to September 2027, followed by ad-hoc security releases until November 2028. (cisco.com)
- End of New Service Attachment passed on 6 Nov 2024, so an uncovered ISR 4321, 4331 or 4351 cannot be added to a new Cisco contract. Existing contracts can be renewed until 5 Feb 2028. (cisco.com)
- Cisco's 4000 Family data sheet (page updated 23 Jun 2026) still says 'The Cisco ISR 4000 Family is orderable and shipping.' For the 4321, 4331 and 4351, the EoL bulletin's End-of-Sale date of 7 Nov 2023 is the authoritative status. (cisco.com)
Keep your ISR 4000 Series (ISR 4321 / 4331 / 4351) covered
Tell us how many you run and when your current cover ends, and we will come back with a like-for-like maintenance quote for that estate. Your model and its support status are attached to the enquiry automatically, so there is nothing to re-type.
Related models
EOL14896 is titled for the ISR4200, ISR4300 and select ISR4400 Series Platform, and this page covers its ISR 4300 trio. Its title names only ISR platforms, so switches in the same estate need checking on their own pages, such as Catalyst 9300 end of life or Nexus 9300 first-generation end of life, or use the server and network end-of-life checker.
- Catalyst 2960-X end of lifeEnd-of-life announced — vendor support still available
- Catalyst 3650 end of lifeEnd-of-life announced — vendor support still available
- Catalyst 3850 end of lifePast the vendor’s last date of support
- Catalyst 9200 end of lifeCurrent — no end-of-life announced
- Catalyst 9300 end of lifeCurrent — no end-of-life announced
- Nexus 9300 (first generation: 9372PX / 9372TX / 9396PX) end of lifePast the vendor’s last date of support
Look up another model in the server & network end-of-life checker, or read what third-party maintenance covers.
Questions people ask about the ISR 4000 Series (ISR 4321 / 4331 / 4351)
Is the Cisco ISR 4331 end of life?
The ISR 4331 is end of sale but not end of support. Cisco stopped selling it on 7 November 2023 under bulletin EOL14896, and its Last Date of Support is 30 November 2028; the ISR 4321 and ISR 4351 share the same dates.
When does Cisco stop supporting the ISR 4321?
Cisco's Last Date of Support for the ISR 4321 is 30 November 2028, which is also its End of Vulnerability/Security Support date. The Brazil-market ISR4321BR/K9 is on a separate bulletin, EOL15204, with a Last Date of Support of 31 January 2029.
Which IOS XE releases are supported on the ISR 4000?
Cisco's bulletin names 17.9.x and 17.12.x as the last supported IOS XE trains for the ISR 4321, 4331 and 4351, and says 17.10.x and 17.11.x are not supported. Bug-fix maintenance ended on 31 August 2025; standard security support for 17.12 runs to September 2027, followed by ad-hoc security releases until November 2028.
What replaces the ISR 4351?
EOL14896 maps ISR4351 PIDs to the Cisco Catalyst 8300 Edge C8300-2N2S-6T, and ISR4321 and ISR4331 PIDs to the Catalyst 8200 Edge C8200-1N-4T. The ISR4331-DC/K9 and -PM20 SKUs have no listed replacement.
Can I get third-party maintenance for ISR 4000 routers?
Cisco closed new service attachment for these routers on 6 November 2024, so an uncovered unit cannot join a new Cisco contract. Third-party providers generally handle hardware faults with diagnosis, spares and engineers, and that cover is not bounded by Cisco's dates; an alternative to Cisco SmartNet explains the approach, and quotes are available on request. Note that Cisco's FN64253 replacement route needs a valid Cisco contract or warranty.
Sources
Every date, rule and specification above was checked against these on 8 October 2026 by an independent verification pass. Vendors revise lifecycle notices; this page is re-checked by 8 January 2027.
- Cisco EOL14896 (Amended, updated 6 Nov 2024): End-of-Sale and End-of-Life Announcement for the Cisco ISR4200, ISR4300 and select ISR4400 Series Platform — cisco.com
- Cisco EOL15204 (updated 27 Oct 2023): End-of-Sale and End-of-Life Announcement for the Cisco ISR4200 and ISR4300 Series Platform for Brazil — cisco.com
- ISR 4000 Series (ISR 4321 / 4331 / 4351) release — cisco.com
- sec.cloudapps.cisco.com — sec.cloudapps.cisco.com
- cisco.com — cisco.com
- cisco.com — cisco.com
- cisco.com — cisco.com
- cisco.com — cisco.com
Last reviewed 7 October 2026. Lifecycle dates for the ISR 4000 Series (ISR 4321 / 4331 / 4351) are re-verified against Cisco's own notices at each review; a date a vendor has not published is never filled in.