• Trainer Sagar Dhawan
• Posted on September 5, 2025
• No Comments

[Day 99] Cisco ISE Mastery Training: Performance Tuning

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Introduction

Performance tuning in Cisco Identity Services Engine (ISE) is not a luxury — it is the difference between a stable NAC deployment and a production outage at scale.
While most engineers focus on policies, authentication, and certificates, many underestimate the engine under the hood: CPU cycles, memory allocation, database health, logging queues, and session handling capacity.

In real-world enterprise environments:

• A single mis-sized ISE node or untuned logging policy can delay authentications by several seconds.
• A burst of endpoint connections (e.g., morning login storm, Wi-Fi reconnections) can overwhelm poorly tuned ISE clusters.
• If Profiling, Posture, and PxGrid are not optimized, they can consume disproportionate resources and starve mission-critical RADIUS transactions.
• Many outages in NAC deployments aren’t caused by bad policy, but by poorly tuned ISE performance parameters.

This module, Day 99 – Cisco ISE Mastery Training: Performance Tuning, is designed as a step-by-step engineering workbook.
I will build a performance baseline, identify tuning levers in ISE, and practice real-time validation using GUI and CLI. By the end of this lab, you will be able to:

• Size and tune ISE nodes for your environment (AuthC/AuthZ/Profiling).
• Configure logging, purge policies, and monitoring thresholds.
• Validate performance tuning in both ISE GUI (Operations → Reports/Monitoring) and ISE CLI (ise/var/logs + show commands).
• Troubleshoot slow authentications, high CPU, and DB bottlenecks.

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Problem Statement

Common pain we must fix systematically:

• High auth latency / timeouts (RADIUS dead, AD slow, TLS handshake slowness).
• PSN CPU spikes / memory pressure during posture or AD outages.
• PAN GUI sluggishness, long saves/commits.
• MnT bloat (slow reports/live logs due to unbounded retention).
• Profiling storms (too many probes; unnecessary CoAs).
• CoA / reauth storms from aggressive NAD timers.
• Load-balancer stickiness issues (hot PSN, cold PSN).
• Replication lag → policy mismatches across PSNs.

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Solution Overview

We tune ISE in layers:

L1 – Platform & OS (VM/Appliance hygiene): CPU/mem reservation, vmxnet3, NTP/DNS reachability.
L2 – Policy & Crypto: tight Allowed Protocols, efficient conditions, EAP-TLS optimization.
L3 – Services: MnT purge, logging levels, profiling probes, posture timers, pxGrid scope.
L4 – Identity: AD site affinity, GC usage, timeouts/retries.
L5 – Network Edges (NAD/LB): RADIUS timers, accounting intervals, LB health/persistence.
L6 – Validation & Observability: Live Logs latency, RADIUS statistics, PSN health CLI, hit counters, policy trace.

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Sample Lab Topology (VMware / EVE-NG)

Compute / VMs

• ISE-PAN/MnT (Primary), ISE-PSN1, ISE-PSN2
• AD/GC + ADCS (CA)
• Linux SFTP (repo for backups/logs)
• Jump host (OpenSSL/curl), Test clients: Windows 11, macOS, iPhone

Network

• Catalyst 9300 (wired 802.1X/MAB)
• WLC 9800 + AP (SSIDs: Corp-8021X, Guest-Portal)
• Optional RADIUS LB in front of PSNs

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Step-by-Step GUI Configuration Guide

A) Baseline & Instrumentation (Measure before changing)

Checklist – Capture Current State

• ISE services up: show application status ise show cpu show memory show disk
• Deployment health (GUI): Administration → System → Deployment (all Green).
• Live Logs latency snapshot: Operations → RADIUS → Live Logs → add column Elapsed Time → export 15–30 min window.
• PSN throughput (NAD side):
  • Catalyst: show radius statistics show aaa servers clear radius statistics
  • WLC 9800: show radius summary
• AD latency (ISE to DCs): Administration → Identity Management → External Identity Sources → Active Directory → Diagnostics.

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B) Platform & VM Hygiene (PSN/PAN/MnT)

1. VM Hardware / Host

• Reserve CPU & Memory for PSNs (avoid overcommit).
• Use vmxnet3 NICs.
• Ensure Datastore latency < 5–10 ms sustained.
• Time sync: NTP reachable & consistent.

Validation

show ntp
show dns
show tech system

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C) Policy Engine Efficiency

1. Allowed Protocols – tighten

• GUI: Administration → System → Settings → Protocols or Policy → Policy Sets → [Set] → Allowed Protocols.
  • Create Custom Allowed Protocols (e.g., only EAP-TLS, PEAP-MSCHAPv2, MAB actually used; remove unused like LEAP).
• Why: Less negotiation/handshake work per request.

Validation

• Live Logs → confirm Tunnel/Inner methods match expectations.
• Switch/WLC debugs show accepted methods (see debug snippets below).

2. Policy Conditions – simplify & order

• GUI: Policy → Policy Sets
  • Use NDG (Network Device Groups) to route requests to the correct set (Site/Device Type) before detailed rules.
  • Replace regex with equals/in-list where possible.
  • Keep specific → general → default order; enable Hit Counters.

Validation

• Observe Hit Counters increasing on expected rules.
• Policy Trace (Live Log → Details → Policy tab) shows matched conditions.

3. Authorization Results – minimize CoA

• Prefer dACL/SGT over constant VLAN flips when possible.
• Use Reauth = No unless posture/registration really needs it.

Validation

• Switch: show authentication sessions interface Gi1/0/10 details show access-lists dynamic
• Live Logs → check fewer CoA events.

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D) Certificates & EAP-TLS handshake tuning

1. Chain completeness & OCSP/CRL reachability

• GUI: Administration → System → Certificates
  • Ensure Root & Intermediates installed under Trusted Certificates.
  • Ensure EAP/Portal cert bound to PSNs.
• Keep CRL/OCSP endpoints reachable to avoid handshake stalls.

Validation

openssl s_client -connect <PSN-FQDN>:443 -showcerts </dev/null | openssl x509 -noout -issuer -subject

• Live Logs → check Step: TLS handshake timings.

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E) Active Directory Efficiency

1. Join & Sites

• GUI: Identity Management → External Identity Sources → Active Directory
  • Ensure node Joined.
  • In Advanced Settings, prefer closest DCs/GCs (Site affinity).
  • Enable machine auth caching (per session by design).

Validation

• AD Diagnostics (Test User).
• CLI: show logging application ise-psc.log | include ad

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F) MnT (Monitoring) – Purge & Logging

1. Set Purge Policies

• GUI: Administration → System → Settings → Purge (or Maintenance → Purge, depending on version)
  • Define retention days for RADIUS/TACACS/Posture records to match storage.
  • Enable automatic purge.

2. Logging Levels

• GUI: Administration → System → Logging → Log Categories
  • Keep at INFO in production. Use DEBUG only during short troubleshooting windows.

Validation

• GUI: Operations → Reports load time improved.
• CLI: show disk show logging application

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G) Profiling – Reduce Noise

1. Probe selection

• GUI: Work Centers → Profiler → Settings
  • Enable only necessary probes (RADIUS, DHCP, SNMP, HTTP) for your environment.
  • Disable NetFlow/IF-MAP/ERSPAN if unused.
  • Avoid profiling CoA unless strictly needed.

2. Profile Policy order

• GUI: Work Centers → Profiler → Profiling Policies
  • Order specific signatures above generic to minimize evaluations.

Validation

• Live Logs → fewer “Profile updated” events.
• PSN CPU steadier during endpoint churn.

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H) Posture – Control Reassessment & CoA

1. Posture Reassessment

• GUI: Policy → Posture
  • Set Reassessment to reasonable intervals (e.g., 12–24h, not minutes).
  • Use Low-impact redirects and limited dACL during Non-Compliant.

Validation

• Live Logs: ensure NonCompliant → Compliant transitions with one CoA per cycle.
• Endpoint agent shows expected Reassessment interval.

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I) pxGrid – Scope & Keepalives

1. Client scope

• GUI: Work Centers → pxGrid Services → Client Management
  • Approve only necessary clients; limit to needed topics.
  • Avoid excessive bulk pulls during business hours.

Validation

• pxGrid clients show Online; PSN CPU stable.

[Screenshot: pxGrid – Client Management]

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J) Replication & Database Health

1. Replication status

show replication status

• Must be SUCCESS on all nodes.

2. Keep policies consistent

• After bulk changes, give time for sync before a load test.

Validation

• GUI: Administration → System → Deployment → Replication Status.

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K) NAD (Switch/WLC) Timers & RADIUS Behavior

Catalyst (example)

aaa new-model
radius server ISE1
 address ipv4 <PSN1>
 key <secret>
radius server ISE2
 address ipv4 <PSN2>
 key <secret>
aaa group server radius ISE-GRP
 server name ISE1
 server name ISE2
aaa authentication dot1x default group ISE-GRP
aaa authorization network default group ISE-GRP
aaa accounting update periodic 15
aaa accounting dot1x default start-stop group ISE-GRP

dot1x system-auth-control
interface Gi1/0/10
 authentication order mab dot1x
 authentication priority dot1x mab
 authentication port-control auto
 mab
 authentication periodic
 authentication timer reauthenticate 3600
 dot1x timeout tx-period 10
 dot1x max-reauth-req 3
 spanning-tree portfast

WLC 9800 (snippets)

aaa servers radius
 radius server <PSN1-IP> auth-port 1812 acct-port 1813 key 7 <secret>
 radius server <PSN2-IP> ...
radius load-balance disable  ! (or enable per design)
aaa deadtime 10

Validation

# Catalyst
show radius statistics
show authentication sessions
show aaa servers
# WLC
show radius summary
show client detail <mac>

• Watch: avoid too-frequent aaa accounting update periodic intervals; set ~15 min unless you need granular accounting.

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L) Load-Balancer (LB) for PSNs – Health & Persistence

• Health check: Real RADIUS Access-Request/Access-Accept style probes (not just TCP/ICMP).
• Persistence: Stick by Calling-Station-ID or Framed-IP (per session), not by NAT’d source IP.
• Timeouts: LB timeout < NAD timeout, so LB fails over before NAD gives up.

Validation

• LB shows both PSNs healthy; client authentications distribute evenly.
• On PSNs, show logging application ise-radius.log shows balanced traffic (per PSN).

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M) After-Tuning Validation (Golden Tests)

GUI

• Live Logs median Elapsed Time improves.
• Deployment Green; Replication SUCCESS.
• Reports load faster; purge jobs executed.

CLI – ISE

show application status ise
show cpu
show memory
show disk
show replication status
show logging application | include (radius|replication|ad|posture|pxgrid|error)

CLI – Catalyst/WLC

show radius statistics
show aaa servers
show authentication sessions
show client detail <mac>

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Performance Tuning Validation Matrix:

Tuning Area	What to Check	How to Validate (GUI)	How to Validate (CLI)	Expected Outcome
System Health (CPU/Memory)	Verify ISE node resources are not overloaded	Administration → System → Deployment → Node Status [Screenshot: Node Status GUI]	show cpu usage show memory statistics	CPU < 70% avg, Memory < 75% sustained
Disk Utilization	Check DB/log storage	Administration → System → Logging → Local Log Storage	show disk	≥ 20% free disk space; alert thresholds not exceeded
Database Performance	Check for DB bottlenecks (Postgres)	Operations → Reports → System → ISE Database Status	show application status ise ise-db-replication	DB running healthy, no replication lag
RADIUS Auth Throughput	Validate peak authentication handling	Operations → Reports → Authentication → RADIUS Live Logs [Screenshot: RADIUS Logs]	Monitor live via: tail -f /var/log/radius.log	RADIUS auth delay < 300ms; no dropped packets
Session Concurrency	Validate concurrent sessions capacity	Operations → Reports → Endpoints and Users → Active Sessions	show session counts	Sessions scale as per node sizing (e.g., 50k per PSN)
Profiling Services	Ensure profiling probes not overloading system	Administration → System → Settings → Profiler	show profiler statistics	Probe CPU < 10% load; no backlog
Posture/Compliance	Check posture load and posture logs	Operations → Reports → Posture → Posture Summary	tail -f /var/log/ise-posture.log	Posture checks completing in < 5s avg
PxGrid Services	Validate pxGrid stability	Administration → pxGrid Services → Clients	show application status ise show pxgrid connections	PxGrid stable, no drops, connected clients visible
Logging/Alarms	Check logging policy & purge	Administration → System → Logging → Purge Policy	ls -lh /opt/ise/logs/	Logs rotating properly; no FS over-utilization
Replication (Cluster)	Validate replication between nodes	Administration → System → Deployment → Replication Status	show replication status	Replication state = “SUCCESS”; sync < 5s delay

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FAQs – Cisco ISE Performance Tuning

Q1. How can I quickly check if my ISE node is overloaded?

Answer:

• GUI:
  • Navigate to: Administration → System → Deployment → Node Status.
  • Look at CPU, memory, and disk utilization indicators.
• CLI: show cpu usage show memory statistics show disk
• Validation: CPU < 70% sustained, Memory < 75%, Disk ≥ 20% free.
  If any threshold is breached, plan scaling or tune policies.

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Q2. What are the main ISE logs to monitor for performance bottlenecks?

Answer:

• RADIUS Authentication: /var/log/radius.log
• Posture: /var/log/ise-posture.log
• Database: /var/log/postgres/
• System Core: /var/log/messages
• Use: tail -f /var/log/radius.log tail -f /var/log/ise-posture.log
• GUI path: Operations → Reports → Authentication → Live Logs.

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Q3. How do I tune ISE for large-scale authentications (e.g., 50k users)?

Answer:

• Use dedicated Policy Service Nodes (PSNs) for authentications.
• Enable Load Balancers in front of PSNs.
• Validate via:
  • GUI: Operations → Reports → Active Sessions
  • CLI: show session counts show logging application ise-psc.log

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Q4. How do I check if replication between nodes is healthy?

Answer:

• GUI: Administration → System → Deployment → Replication Status.
• CLI: show replication status
• Healthy state should be SUCCESS with sync delay < 5 seconds.
  If “FAILED” → restart replication service or check NTP sync.

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Q5. My ISE authentication latency is high (>500ms). How do I troubleshoot?

Answer:

1. Check PSN CPU/memory load (see Q1).
2. Verify RADIUS logs for timeouts. grep "Response-Time" /var/log/radius.log
3. Ensure network latency < 20ms between NADs and PSN.
4. If DB lagging → check replication status and database statistics.

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Q6. What are the best practices for ISE log storage tuning?

Answer:

• Set purge policies:
  • GUI: Administration → System → Logging → Purge Policy.
• CLI check disk usage: show disk
• Always maintain ≥ 20% free space.
• For heavy deployments → forward logs to an external Syslog/Splunk server.

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Q7. How do I tune profiling so it doesn’t overload ISE?

Answer:

• GUI: Administration → System → Settings → Profiler.
• Disable unnecessary probes (e.g., NetFlow if unused).
• CLI: show profiler statistics
• Keep probe CPU utilization < 10%.
  If higher, consider a dedicated Profiling Node.

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Q8. How can I validate pxGrid service stability?

Answer:

• GUI: Administration → pxGrid Services → Clients.
• CLI: show application status ise show pxgrid connections
• Clients should appear “Connected”.
• If disconnects occur → check firewall ports (8910/8911) and system certificates.

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Q9. What database tuning is possible in ISE?

Answer:

• ISE uses Postgres; tuning is limited but you can:
  • Monitor DB health: show application status ise
  • GUI: Operations → Reports → System → ISE Database Status.
• If DB is overloaded → add more PSNs or reduce logging verbosity.
• Avoid manually tuning Postgres (unsupported by TAC).

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Q10. How do I plan scaling ISE for performance?

Answer:

• Cisco recommends:
  • Small: 2 nodes (Admin + PSN combined).
  • Medium: 4–6 nodes (Dedicated Admin/PSN/Monitoring).
  • Large Enterprise: 10+ nodes with Load Balancing.
• CLI for session tracking: show session counts
• GUI for monitoring: Operations → Reports → Active Sessions.
• Always follow the Cisco ISE Performance & Scale guide for version-specific numbers.

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YouTube Link

For more in-depth Cisco ISE Mastery Training, subscribe to my YouTube channel Network Journey and join my instructor-led classes for hands-on, real-world ISE experience

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Closing Notes

Performance tuning = discipline + measurement. Start with baseline, apply one change at a time, and validate: Live Logs latency, PSN health, NAD statistics, and replication. Keep policies lean, purge MnT, right-size timers, and balance PSN load.

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Upgrade Your Skills – Start Today

For more in-depth Cisco ISE Mastery Training, subscribe to my YouTube channel Network Journey and join my instructor-led classes.

Fast-Track to Cisco ISE Mastery Pro

• I run a focused 4-month instructor-led CCIE Security track with live ISE labs focused on scaling + performance (policy optimization, PSN/LB tuning, MnT purge strategy, AD/site design, posture load control).
• Course outline & enrollment: https://course.networkjourney.com/ccie-security/
• Next step: Fill the intake form → free readiness call + performance lab checklist → secure your seat.

Enroll Now & Future‑Proof Your Career
Email: info@networkjourney.com
WhatsApp / Call: +91 97395 21088

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