How to Audit a Cisco IOS Router: Step-by-Step Security Guide
Auditing a Cisco IOS router means systematically checking its configuration against proven security benchmarks and identifying every gap before an attacker does. This guide walks you through the full process — from pulling the config to prioritizing findings and applying fixes — with commands you can use right now.
Table of Contents
Prerequisites and Scope
Before starting a router security audit, get clear on two things: authorization and scope.
Authorization: Only audit devices you own or have written authorization to assess. Running security checks against network infrastructure without permission may violate computer fraud laws regardless of intent.
Scope: A configuration-based audit covers the security posture of the device’s software configuration. It does not cover physical security, firmware vulnerabilities, or network architecture. Think of it as one layer in a comprehensive security program, not the whole thing.
For this guide you’ll need read access to the router (show running-config), a text editor to save the output, and a browser to run the free router audit tool.
Step 1: Collect the Router Configuration
Pull the complete running configuration — this reflects the actual current state of the device, not the startup config saved to NVRAM.
! Disable pagination first, then pull the full config
Router# terminal length 0
Router# show running-configCopy everything from Building configuration... to the final end statement. The terminal length 0 command prevents “–More–” pagination prompts from interrupting the output.
Sensitive data note: Router configurations often contain password hashes, SNMP community strings, and BGP MD5 keys. Handle the saved config as a credential file — don’t store it in unsecured locations or email it unencrypted.
Pulling Specific Sections
IOS-XE supports section filtering if you only need to review specific areas:
! Show only VTY line configuration
Router# show running-config | section line vty
! Show only interface configurations
Router# show running-config | section interface
! Show SNMP configuration
Router# show running-config | include snmpStep 2: Run an Automated Router Audit
Manual auditing is time-consuming and error-prone. A single Cisco IOS configuration can be thousands of lines. The fastest approach is to run the config through an automated tool that checks all rules simultaneously.
Paste your running configuration
Paste the full output of show running-config into the text area. The tool accepts configs of any size.
Click “Run Audit”
The engine processes the config entirely in your browser using JavaScript. Zero data is transmitted to any server — verify this in DevTools → Network tab.
Review your security score and findings
You receive a score out of 100, a severity breakdown (Critical / High / Medium / Low), and a detailed list of every check with pass/fail status and remediation guidance.
Audit Your Cisco Router Right Now
60+ checks. Free. No login. Nothing leaves your browser.
Run Free Audit →Step 3: Key Areas to Check Manually
The automated tool catches the most important issues, but a thorough audit also includes manual review of areas that require judgment rather than pattern matching.
ACL Logic Review
An automated tool can verify that an ACL is applied to a VTY line or interface, but it cannot judge whether the ACL permits or denies the right addresses. Review every ACL manually:
Router# show ip access-lists
! Review each ACL for:
! - Overly permissive entries (permit any any)
! - Missing deny entries at the end
! - Correct source/destination addresses for management ACLs
! - Correct application direction (in vs out)User Account Review
Check that only authorized accounts exist with appropriate privilege levels:
Router# show running-config | section username
! Look for:
! - Accounts that shouldn't be there
! - Privilege 15 accounts (full admin) — should be minimal
! - Accounts using 'password' instead of 'secret'Routing Protocol Neighbors
Verify routing protocol authentication is in place and only expected neighbors are established:
Router# show ip ospf neighbor
Router# show ip bgp summary
Router# show ip eigrp neighbors
! Unexpected neighbors could indicate route injection attacksActive Services Check
Router# show control-plane host open-ports
! Lists all open ports on the management plane
! Any unexpected service here is worth investigatingMost Common Cisco IOS Security Findings
Across thousands of Cisco router audits, the same issues appear repeatedly. Here are the most frequently found vulnerabilities ranked by severity:
| Finding | Severity | Config Check |
|---|---|---|
| Telnet enabled on VTY lines | Critical | transport input ssh missing |
| Enable password (not secret) in use | Critical | enable secret not configured |
| No exec timeout on VTY lines | High | exec-timeout 0 0 or missing |
| HTTP server enabled | High | ip http server present |
| SNMP with default community strings | High | snmp-server community public |
| No AAA configured | High | aaa new-model absent |
| No login banner | Medium | banner login absent |
| IP source routing enabled | Medium | no ip source-route absent |
| CDP enabled on external interfaces | Medium | no cdp enable missing on WAN int |
| No NTP configured | Low | ntp server absent |
| No remote syslog server | Low | logging host absent |
Step 4: Apply Remediation
Work through findings in severity order — Critical first, then High, Medium, Low. Schedule changes in a maintenance window and have a rollback plan ready.
Disable Telnet, enable SSH-only access:
! Generate RSA keys (minimum 2048-bit)
Router(config)# crypto key generate rsa modulus 2048
Router(config)# ip ssh version 2
Router(config)# ip ssh time-out 60
Router(config)# ip ssh authentication-retries 3
!
Router(config)# line vty 0 15
Router(config-line)# transport input ssh
Router(config-line)# login local
Router(config-line)# exec-timeout 10 0Replace enable password with enable secret:
Router(config)# no enable password
Router(config)# enable algorithm-type scrypt secret YourStrongPassword123!Disable HTTP server and unnecessary services:
Router(config)# no ip http server
Router(config)# no ip http secure-server
Router(config)# no ip source-route
Router(config)# no service tcp-small-servers
Router(config)# no service udp-small-servers
Router(config)# no ip fingerRemove default SNMP community strings:
Router(config)# no snmp-server community public
Router(config)# no snmp-server community private
! If SNMP is required, use SNMPv3
Router(config)# snmp-server group SNMP3GROUP v3 priv
Router(config)# snmp-server user SNMPUSER SNMP3GROUP v3 auth sha AuthPass priv aes 128 PrivPassEnable AAA:
Router(config)# aaa new-model
Router(config)# aaa authentication login default local
Router(config)# aaa authorization exec default local
Router(config)# aaa accounting exec default start-stop localStep 5: Document and Re-Audit
Security audits are only defensible if the process is documented. After applying remediations, re-run the audit with the updated config and compare before/after scores. Save the report with your change records. Note any accepted risks — if you couldn’t fix something immediately, document why and when you’ll address it. Schedule recurring audits quarterly, and any time a significant change is made.
Compliance tip: For PCI DSS Requirement 1 and NIST 800-53 CM-6, you need evidence of regular configuration reviews. An audit report with a timestamp and before/after scores is exactly the documentation auditors look for.
Frequently Asked Questions
enable secret, service password-encryption, ip ssh version 2, no ip http server, aaa new-model, no ip source-route, and restricting VTY transport to SSH. These address the most commonly exploited weaknesses.Ready to Audit Your Cisco Router?
Free. No login. 60+ checks. Nothing sent to any server.
Run Your Free Audit Now →