Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries)
By Sai Kiran Pandrala · reviewed by Sai Kiran Pandrala, Editor Last verified: 2026-05-30
| Category | IP / Network Issue |
|---|---|
| Subject | Cisco ASA firewall |
| Skill level | Intermediate to advanced (CCNA / CCNP background recommended) |
| DIY-able? | Mostly yes with CLI access; some scenarios need TAC + RMA. |
What this guide covers
Switch TCAM is full, routes or ACL entries are getting punted to CPU.
Resolve
show platform tcam utilizationshows TCAM usage by region.- If route-table exceeds platform limit: enable SDM template that prioritises routing:
sdm prefer routing. - If ACL exceeds limits: simplify ACLs or split across multiple devices.
- Long-term: refresh to a higher-tier model with bigger TCAM.
CLI commands
show platform tcam utilization
show sdm prefer
sdm prefer routing
reload
When the issue persists
- Open Cisco TAC case with
show tech-support. - Provide the full timeline + recent changes.
Frequently asked questions
Will this work on my exact IOS-XE / ASA version?
The procedure reflects current IOS-XE 17.x and ASA 9.20 behaviour. Older trains (15.x, 9.16 ASA) may need minor syntax adjustments. use ? in the CLI.
Should I open a TAC case immediately?
Open one if you suspect hardware failure or the symptom persists after a maintenance-window reload. Make sure your SmartNet is active first.
Where can I find the Cisco official documentation?
https://www.cisco.com/c/en/us/support/all-products.html, search the product family + feature name.
Is this procedure safe in production?
Test in a lab or maintenance window first. Capture pre-change state so you can roll back.
Related guides
- All Cisco fix guides → /cisco/
- Cisco IOS error messages → /cisco/section/ios_error_messages.html
- Cisco troubleshooting by symptom → /cisco/section/troubleshoot_symptoms.html
References
- Cisco System Message Guide for IOS-XE / IOS
- Cisco Bug Search Tool: https://bst.cloudapps.cisco.com/bugsearch/
- Cisco Smart Software Manager: https://software.cisco.com
- Cisco TAC: https://mycase.cloudapps.cisco.com/case
Reference material, not professional advice. Validate against your specific IOS-XE version and test in a non-production environment before applying.
What changed recently?
Fault diagnosis on a Cisco device goes faster when you map the symptom to a recent change:
- Did firmware update in the last 7 days?
- Did the network (router, ISP, VPN) change?
- Was the device moved physically?
- Did paired devices (phone, hub, app) update?
- Were any accessories swapped in or out?
The answer narrows the root cause to a manageable subset.
Isolate
A few things to confirm so the Cisco device fix goes cleanly:
- Latest firmware downloaded if you're going to update.
- Warranty + support contract status checked: opening sealed parts may void it.
- Backup of current configuration (where applicable) taken.
- Spare parts on hand if you anticipate replacement.
- Adequate workspace, lighting, and time, rushing causes regressions.
Validate
After applying the fix on your Cisco device, confirm:
- The original symptom is no longer reproducible.
- Related features (status LEDs, app sync, paired accessories) still work.
- The device responds to a soft reboot without the fault returning.
- Any error codes that were on display have cleared.
- Documentation (your service log, the brand companion app) reflects the change.
Escalation guide
For a Cisco device, the right escalation depends on impact:
- Cosmetic / minor: log a ticket via the Cisco app or web portal. Response 1-3 business days.
- Mid-impact: phone support. Have your serial number ready.
- Critical (production down, safety issue): in-person dealer / TAC visit. Bring proof of purchase.
- Out of warranty: third-party repair shop with manufacturer-certified technicians.
More frequently asked questions
Should I update firmware first or last?
Update firmware first if a release note specifically mentions your symptom. Otherwise, finish the troubleshooting flow first, then update; that way you can isolate whether the update or the underlying fix solved it.
What if the fix returns after a reboot?
Persistent fault returns mean either: a hardware fault (escalate), a configuration that's being overwritten by a sync source (check cloud profiles), or a regression in a recent firmware update (rollback).
How often should I run preventive checks?
Quarterly for most consumer devices; monthly for production / commercial devices. Set a calendar reminder so the device stays healthy between issues.
Why is this happening on a brand-new unit?
Out-of-box defects do occur. If you've owned the device under 30 days and the symptom persists after a factory reset, escalate to the seller for replacement under DOA terms before opening a manufacturer support case.
What if my model isn't exactly the same revision?
Cross-check the model code on the rating plate against the manufacturer support page. Major firmware generations sometimes shift the menu path; the option is usually under a similarly-named section.
Field notes from real incidents on IP / Network Issue
When I work on Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries) the rhythm I lean on is the one I have built over years of these tickets, not a stack of generic advice. Most catalyst stack issues I have triaged were power-budget related, not software. the show power detail output answers it in 5 seconds. I never run a software upgrade on a live Catalyst stack without an out-of-band console session; the in-band session drops at the worst possible moment.
Cisco bug search tool is the cheapest sanity check before a config change, search the symptom, sort by affected releases, decide. The newer Cisco IOS-XE traceability tools (show platform hardware fed) are massively underused; they answer questions the old CLI cannot. Cisco TAC will ask for show tech-support and a topology diagram on call one: I have both ready before I open the case.
Tools I actually reach for
For Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries) on IP / Network Issue the cheapest signal I can land usually comes from a known order of operations, not a kitchen-sink approach. I start with ping vrf <vrf> <target> because it is the lowest-friction way to confirm the failure is real and reproducible. If that returns ambiguous data, I escalate to packet capture on the ingress interface (TAC will ask for it), show logging last 200, and finally to show tech-support (capture for TAC) only when the cheaper tools cannot reach the layer the failure lives in. That ordering matches the failure surfaces I have actually seen on IP / Network Issue units over the last few years, not an abstract taxonomy. The cheap signals gate the expensive ones so the investigation does not balloon into a multi-hour exercise.
Verification I run before I close the ticket
Before I mark Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries) resolved on a IP / Network Issue unit, the verification loop below is what I actually run. Each step proves a different layer is green, and the order matters - the cheap checks gate the more expensive ones so I never burn an hour on a deep test that a shallow one would have failed in seconds.
show spanning-tree summary # confirm topology stabilityIf that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.
show interfaces <int> | include errors|drops|CRCIf that one comes back clean, move to the next check. If it does not, stop and dig in there before layering more verification on top of a red signal.
show bgp summary # confirm session state after route changesOnly when every line above runs clean do I close the ticket and update the runbook with the timestamps. A green verification that nobody can reproduce is not a fix, it is luck waiting to regress.
Where I check first when the docs disagree
When two sources contradict each other on a IP / Network Issue detail, the disambiguation order I lean on is stable across products and across years. cisco.com/c/en/us/support, official command references is where I start for the ground-truth view. cisco.com/c/en/us/td/docs/ios-xml for IOS XR is where I start for the ground-truth view. developer.cisco.com for NSO / model-driven APIs is where I start for the ground-truth view. Cisco TAC case knowledge base is where I start for the ground-truth view. Random blog posts and reseller wikis are signal, not ground truth, and I treat them as such until the references above either confirm or contradict the claim. The cost of trusting an unauthoritative source on Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries) is rarely worth the time it saved.
Pitfalls I have walked into on this exact path
The shortcuts that look smart on Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries) have a habit of biting back. The pitfalls below are the ones I have personally walked into on a IP / Network Issue unit, not things I read about. Cisco TAC will ask for show tech-support and a topology diagram on call one. I have both ready before I open the case. Most catalyst stack issues I have triaged were power-budget related, not software, the show power detail output answers it in 5 seconds. When in doubt I revert to the slower path that the manual prescribes - the time I save by skipping it is always smaller than the time I spend cleaning up afterwards.
What I tell the next on-call
When I hand Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries) off to the next person on rotation, the three lines I leave in the runbook are these. First, the symptom signature on IP / Network Issue - not a paraphrase, the exact string that surfaces in logs or on the screen. Second, the diagnostic that gave the highest signal in the least time. Third, the exact verification command whose green output justified closing the ticket. That trio is what turns a one-off fix into a runbook entry the next engineer can use without paging me at three in the morning.
I also add a one-line note on the cost of getting this wrong. For Cisco ASA firewall: TCAM exhausted (IPv4 routes / ACL entries) on a IP / Network Issue unit, the cost is rarely the replacement part or the patch itself. It is the downtime, the second site visit, and the trust deficit you spend with whoever owns the asset when the fix does not hold. That framing keeps the next on-call from choosing the cheap-looking shortcut that ends up costing the most in elapsed hours and goodwill.
Related fixes
Related guides worth a look while you sort this one out:
- Cisco router: TCAM exhausted (IPv4 routes / ACL entries)
- Cisco switch: TCAM exhausted (IPv4 routes / ACL entries)
- How to configure access rule (ACL) on Cisco ASA 5506-X
- How to configure access rule (ACL) on Cisco ASA 5508-X
- How to configure access rule (ACL) on Cisco ASA 5516-X
- Cisco ASA firewall all ports dead: Diagnose & Fix
People also ask
Will this work on my exact IOS-XE / ASA version?
The procedure reflects current IOS-XE 17.x and ASA 9.20 behaviour. Older trains (15.x, 9.16 ASA) may need minor syntax adjustments: use `?` in the CLI.
Should I open a TAC case immediately?
Open one if you suspect hardware failure or the symptom persists after a maintenance-window reload. Make sure your SmartNet is active first.
Where can I find the Cisco official documentation?
https://www.cisco.com/c/en/us/support/all-products.html, search the product family + feature name.
Is this procedure safe in production?
Test in a lab or maintenance window first. Capture pre-change state so you can roll back.