Fix GBIC_SECURITY_CRYPT-4-VN_DATA_CRC_ERROR

This is usually caused by using aftermarket GBIC's.

There are two work arounds (variously supported)

config t
service unsupported-transceiver

or

config t
no errdisable detect cause gbic-invalid

You may need to reload the switch or re-seat the GBIC's to get them working.

Block Outbound Port 25 SMTP Traffic Cisco Catalyst Switch ACL

Log into to your switch, enter "enable" mode, then "configure terminal" mode:

access-list 199 deny tcp any any eq smtp
access-list 199 permit ip any any

Now, on any interface that you want to deny outbound port 25 SMTP traffic to:

ip access-group 199 in

Write out the changes and you're done

View And Disconnect Users Logged Into A Cisco Switch Or Router

To view users logged in:

show line

To disconnect a user:

clear line [line # from above]

Remove All Non-Standard Vlans On Cisco Switches

Inside terminal configuration:

no vlan 2-1000

Then wr the changes

GREP/Search For A Term In Cisco Command Output

You simply use:

[command] | include [Term]

So on a fresh 24 port C3750G:

show config | include  GigabitEthernet1

Would render:

interface GigabitEthernet1/0/1
interface GigabitEthernet1/0/2
interface GigabitEthernet1/0/3
interface GigabitEthernet1/0/4
interface GigabitEthernet1/0/5
interface GigabitEthernet1/0/6
interface GigabitEthernet1/0/7
interface GigabitEthernet1/0/8
interface GigabitEthernet1/0/9
interface GigabitEthernet1/0/10
interface GigabitEthernet1/0/11
interface GigabitEthernet1/0/12
interface GigabitEthernet1/0/13
interface GigabitEthernet1/0/14
interface GigabitEthernet1/0/15
interface GigabitEthernet1/0/16
interface GigabitEthernet1/0/17
interface GigabitEthernet1/0/18
interface GigabitEthernet1/0/19
interface GigabitEthernet1/0/20
interface GigabitEthernet1/0/21
interface GigabitEthernet1/0/22
interface GigabitEthernet1/0/23
interface GigabitEthernet1/0/24
interface GigabitEthernet1/0/25
interface GigabitEthernet1/0/26
interface GigabitEthernet1/0/27
interface GigabitEthernet1/0/28

As a side note, the search term is case sensitive

Add Or Change User Password On Cisco Switches

This assumes you are already in enabled mode:

#> config t
#> username [username] password [password]

Add Or Change Enable Mode Password On Cisco Switches

This assumes you are already in enabled mode:

#> config t
#> enable secret [password]

Enable Password Encyption On Cisco Switches

This assumes you are already in enabled mode:

#> config t
#> service password-encryption