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Network Verification and Testing

Systematic approach to verify network configurations and identify issues - check settings, test connectivity, and validate security policies.

Verify Trunk Configuration

Section titled “Verify Trunk Configuration”

Check if interface is configured as trunk and which VLANs are allowed.

Switch# show interfaces trunk

Typical output:

Port        Mode         Encapsulation  Status        Native vlan
Gig0/1      on           802.1q         trunking      1


Port        Vlans allowed on trunk
Gig0/1      20,21,22,23,30


Port        Vlans allowed and active in management domain
Gig0/1      20,21,22,23,30

Check specific interface:

Switch# show interfaces GigabitEthernet0/1 switchport

Key fields to check:

  • Administrative Mode: trunk (should be trunk)
  • Operational Mode: trunk (confirms it’s actually trunking)
  • Trunking VLANs Enabled: (verify correct VLANs are allowed)

Verify Password Encryption

Section titled “Verify Password Encryption”

Check if passwords are encrypted in configuration.

Switch# show running-config | include password

Look for:

  • service password-encryption (should be present)
  • enable secret 5 $1$mERr$... (encrypted with MD5)
  • username admin secret 5 $1$mERr$... (encrypted)

Bad example (unencrypted):

enable password cisco123
username admin password WELkom@1

Good example (encrypted):

enable secret 5 $1$mERr$hx5rVt7rPNoS4wqbXKX7m0
username admin secret 5 $1$mERr$9cTjUIEqNNIjz7kF4sFr1.
service password-encryption

Verify SSH and Disable Telnet

Section titled “Verify SSH and Disable Telnet”

Check remote access methods.

Switch# show running-config | section line vty

Correct configuration (SSH only):

line vty 0 4
 login local
 transport input ssh

Incorrect (Telnet enabled):

line vty 0 4
 login local
 transport input telnet ssh

Verify SSH is enabled:

Switch# show ip ssh

Test SSH connectivity:

laptop> ssh admin@10.30.0.4

Verify Enable Password/Secret

Section titled “Verify Enable Password/Secret”

Check if privileged EXEC mode is protected.

Switch# show running-config | include enable

Look for:

  • enable secret 5 $1$mERr$... (best - MD5 encrypted)
  • OR enable password 7 ... (weaker - Type 7 encryption)

Missing enable protection (security issue):

! No enable command found

Fix:

Switch(config)# enable secret WELkom@1

Verify NTP Configuration

Section titled “Verify NTP Configuration”

Check if device is synchronized with NTP server.

Switch# show running-config | include ntp

Expected output:

ntp server 10.30.0.100

Verify NTP synchronization:

Switch# show ntp status

Check NTP associations:

Switch# show ntp associations

Typical output:

  address         ref clock     st  when  poll reach  delay  offset    disp
*~10.30.0.100    .GPS.          1    64    64   377   0.50   -0.23    0.12
 * sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured

Verify Syslog Configuration

Section titled “Verify Syslog Configuration”

Check if logging to syslog server is configured.

Switch# show running-config | include logging

Expected output:

logging host 10.30.0.100
logging trap informational

Verify logging status:

Switch# show logging

Key information:

  • Trap logging: level informational, <number> message lines logged
  • Logging to: 10.30.0.100

If missing, configure:

Switch(config)# logging host 10.30.0.100
Switch(config)# logging trap informational

Verify IOS Version

Section titled “Verify IOS Version”

Check running IOS version and compare to documentation.

Switch# show version

Key information:

  • Cisco IOS Software, ... Version 12.2(25r) (version number)
  • System image file is "flash:c2960-lanbasek9-mz.122-25r.bin"

Quick version check:

Switch# show version | include IOS

Compare against expected versions from documentation table.

Test Connectivity with Ping

Section titled “Test Connectivity with Ping”

Basic connectivity test between devices.

Ping from PC to server:

PC> ping 10.10.0.100


Reply from 10.10.0.100: bytes=32 time<1ms TTL=128
Reply from 10.10.0.100: bytes=32 time<1ms TTL=128
Reply from 10.10.0.100: bytes=32 time<1ms TTL=128
Reply from 10.10.0.100: bytes=32 time<1ms TTL=128

Ping from router with source interface:

Router# ping 10.10.0.100 source GigabitEthernet0/0/0

Extended ping (more options):

Router# ping
Protocol [ip]:
Target IP address: 10.10.0.100
Repeat count [5]: 10
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: 10.30.0.1
Type of service [0]:
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:

Test HTTP/Web Access

Section titled “Test HTTP/Web Access”

Test if PC can reach intranet web server.

From PC command prompt:

PC> ping 10.10.0.100

Open browser and navigate to:

http://10.10.0.100

From router/switch (if HTTP client available):

Switch# telnet 10.10.0.100 80

If connection succeeds, HTTP port is open.

Verify VLAN Configuration

Section titled “Verify VLAN Configuration”

Check if VLANs exist and which ports are assigned.

Switch# show vlan brief

Typical output:

VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa0/24
20   Productie                        active    Fa0/1, Fa0/2, Fa0/3, Fa0/4, Fa0/5
21   KlantenService                   active    Fa0/6, Fa0/7, Fa0/8, Fa0/9, Fa0/10
22   HRM                              active    Fa0/11, Fa0/12, Fa0/13, Fa0/14, Fa0/15
23   Marketing                        active    Fa0/16, Fa0/17, Fa0/18, Fa0/19, Fa0/20
30   IT_Beheer                        active    Fa0/24
99   Ongebruikt                       active    Fa0/21, Fa0/22, Fa0/23

Verify specific port assignment:

Switch# show interfaces FastEthernet0/1 switchport | include Access Mode VLAN

Verify IP Addresses

Section titled “Verify IP Addresses”

Check if correct IP addresses are configured.

Switch# show ip interface brief

Typical output:

Interface              IP-Address      OK? Method Status                Protocol
Vlan30                 10.30.0.4       YES manual up                    up
GigabitEthernet0/1     unassigned      YES unset  up                    up

Detailed interface info:

Switch# show ip interface Vlan30

Verify Routing

Section titled “Verify Routing”

Check if routes exist to reach remote networks.

Router# show ip route

Test specific route:

Router# show ip route 10.10.0.0

Verify gateway reachability:

Router# ping 172.16.0.1

Verify Interface Status

Section titled “Verify Interface Status”

Check if interfaces are up and operational.

Switch# show interfaces status

Typical output:

Port      Name               Status       Vlan       Duplex  Speed Type
Fa0/1     Productie          connected    20         a-full  a-100 10/100BaseTX
Fa0/2     Productie          connected    20         a-full  a-100 10/100BaseTX
Fa0/24    IT_Beheer          connected    30         a-full  a-100 10/100BaseTX
Gig0/1    Trunk to Core      connected    trunk      a-full a-1000 10/100/1000BaseTX

Check specific interface:

Switch# show interfaces GigabitEthernet0/1

Look for:

  • GigabitEthernet0/1 is up, line protocol is up (should be up/up)
  • Full-duplex, 1000Mb/s

Create Verification Checklist

Section titled “Create Verification Checklist”

Use this template for systematic verification:

Check ItemDevice(s)CommandExpected ResultStatusIssue
Trunk VLANsSW1-SW3show interfaces trunkVLANs 20,21,22,23,30❌SW3 allows all VLANs
Telnet disabledAllshow run | section vtytransport input ssh✅-
Passwords encryptedAllshow run | include secretenable secret 5✅-
Enable password setAllshow run | include enablePresent❌Missing on SW2, SW3
NTP configuredAllshow run | include ntpntp server 10.30.0.100✅-
Syslog configuredAllshow loggingLogging to 10.30.0.100✅-
IOS versionAllshow versionPer documentation table❌Multiple version mismatches
Web accessPCsping 10.10.0.100Successful✅-

Common Issues and Fixes

Section titled “Common Issues and Fixes”

Issue: Trunk allows all VLANs instead of specific VLANs

Switch# show interfaces trunk
! Shows: Vlans allowed on trunk: 1-4094


Switch(config)# interface GigabitEthernet0/1
Switch(config-if)# switchport trunk allowed vlan 20,21,22,23,30

Issue: No enable password configured

Switch# show run | include enable
! No output


Switch(config)# enable secret WELkom@1

Issue: Telnet still enabled

Switch(config)# line vty 0 4
Switch(config-line)# transport input ssh

Issue: Passwords not encrypted

Switch(config)# service password-encryption

Issue: Wrong IOS version

Document the discrepancy for management - IOS upgrades require change control process.

Expected: 12.2(25r)
Actual: 12.2(55)SE
Action: Document for upgrade planning