Cisco IOS // Understanding the Defaults

seen on old Catalyst 2950


check default configuration

do show running-config

weak password encryption is already disabled

!no service password-encryption

SNMP is not enabled, no need to forcilbly disable it either

!no snmp-server


ip subnet-zero

historically allows first .0 and last subnets .255


spanning-tree mode pvst
no spanning-tree optimize bpdu transmission
spanning-tree extend system-id

Keepalive loop

you will notice LOOP packets in wireshark, as keepalive is the default. keep it as such as it is required to determine whether an interface is up or not.



What is IP Subnet Zero? - Cisco Articles & Tips

What does ip subnet-zero command do?


Consquences of “no keepalive” on switch port

Error - “%ETHCNTR-3-LOOP_BACK_DETECTED” Catalyst switch that runs Cisco IOSĀ® Software

Disabling keepalive in switch