Category Archives: CCNA

Access Router shortcuts

[Special telnet escape help]
^^B sends telnet BREAK
^^C sends telnet IP
^^H sends telnet EC
^^O sends telnet AO
^^T sends telnet AYT
^^U sends telnet EL

VTP Advertisements

Summary Advertisements
Subset Advertisements

Request Advertisements – When a request advertisement is sent to a VTP server in the same VTP domain, the VTP server responds by sending a summary advertisement and then a subset advertisement.
VTP Client:
In addition, the VLAN configuration information that a VTP client switch receives from a VTP server switch is stored in a VLAN database, not in NVRAM.
VTP Transparent:
In transparent mode, VLAN configurations are saved in NVRAM (but not advertised to other switches), so the configuration is available after a switch reload.

Configuration Revision

Each time a VLAN is added or removed, the configuration revision number is incremented.

A VTP domain name change does not increment the revision number. Instead, it resets the revision number to zero.

The configuration revision number determines whether the configuration information received from another VTP-enabled switch is more recent than the version stored on the switch.

Trunk and VLANs

A trunk is a point-to-point link between two network devices that carries more than one VLAN. A VLAN trunk allows you to extend the VLANs across an entire network.
A VLAN trunk does not belong to a specific VLAN, rather it is a conduit for VLANs between switches and routers.

Data VLAN = data VLAN is sometimes referred to as a user VLAN.

Default VLAN
The default VLAN for Cisco switches is VLAN 1. VLAN 1 has all the features of any VLAN, except that you cannot rename it and you can not delete it.
It is a security best practice to change the default VLAN to a VLAN other than VLAN 1; this entails configuring all the ports on the switch to be associated with a default VLAN other than VLAN 1.

Native VLAN=A native VLAN is assigned to an 802.1Q trunk port.

An 802.1Q trunk port supports traffic coming from many VLANs (tagged traffic) as well as traffic that does not come from a VLAN (untagged traffic).

Management VLAN=A management VLAN is any VLAN you configure to access the management capabilities of a switch.
VLAN 1 would serve as the management VLAN if you did not proactively define a unique VLAN to serve as the management VLAN. You assign the management VLAN an IP address and subnet mask.

Voice VLANs
Tagging refers to the addition of bytes to a field in the data frame which is used by the switch to identify which VLAN the data frame should be sent to.
Static VLAN
Dynamic VLAN

Voice VLAN – Before you configure a voice VLAN on the port, you need to first configure a VLAN for voice and a VLAN for data.
1-1005, and an extended range, 1006-4094
inter-switch link (ISL),
two types of trunk ports, IEEE 802.1Q and ISL, today only 802.1Q is used.

Trunking Modes
On (default)
Dynamic auto If both ports on the switches are set to auto, they do not negotiate to be in a trunking state. They negotiate to be in the access (non-trunk) mode state.
Dynamic desirable

Collision Domains

What is a collision domain ?

A collision domain represents the end devices that are interconnected via a hub or a series of hubs. A collision domain is also referred to as a network segment. Hubs and repeaters therefore have the effect of increasing the size of the collision domain.

Switches allow the segmentation of the LAN into separate collision domains, which means that one port on the switch is one collision domain; the number of ports on the switch gives the number of collision domains, but if you have in the network L1, L2 and L3 devices you have to analyze the network and compute the number of collision domains.

I have a table that you can see (the source table is from here:

Hub/Repeater Doesn’t Split Doesn’t Split
Switch/Bridge Does Split Doesn’t Split (By default)
Can be done through VLAN
Router Does Split Does Split

To have a better understanding watch Dan’s explication from

If the video does not work, click here:


When clearing the OSPF process in Packet Tracer instead of using the command clear ip ospf process, because it is not supported by Packet Tracer [..]

CCNA1 activity 6.8.1 skills integration challenge planning subnets

If you get 95% with both static route and static default route in place do not worry.

There is a misconfiguration in the activity. Use these to get […]

interfetele seriale au IP-urile cu 121 si 122, dar rutele statice au ca next-hop 129 si 130; deci pentru 100%: o ruta statica default cu next-hop= pe R2-Central

Basic configuration on devices

Basic configuration on devices:

  • set hostname;
  • set secret password;
  • set banner motd;
  • encrypt passwords;
    • line console 0

    • set synchronous logging
    • set idle time
    • set password
    • use login
    • line vty 0 15

    • set password
    • use login
    • set history size

Below you have the commands. The hostname is at the end, because if you want to copy-paste them, you will have to modify the hostname:

conf t
enable secret cisco
service password-encryption
line console 0
logging synchronous
exec-time 0 0
password cisco
history size 256
line vty 0 15
password cisco
history size 256