Below is a short overview of STP and how to navigate it in the CISCO IOS enjoy.
[youtube=http://www.youtube.com/watch?v=zapAZRP7mEk&w=560&h=315]
STP Overview Video
December 12, 2013
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Posted by Josh Gahan
Switch IP & Default Gateway Checklist
June 7, 2013- Enter VLAN1 configuration mode using the Interface VLAN 1 global configuration command
- Assign an IP address and mask using the IP address ip address mask interface sub-command
- Enable the VLAN1 interface using No shutdown interface subcommand
- Add the IP default-gateway ip address global command to configure the default gateway
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Posted by Josh Gahan
Three most Common Types of Attacks
May 30, 2013Denial of Service (DoS)
- Erasers try to harm the host, destroying hardware and files
- Crashers cause hosts to fail or no longer allow hosts to connect to the network
- Flooders flood the network with packets to make the network unusable.
Reconnaissance Attacks
- The goal is to gather information to perform an access attack and causing harm can be a side effect.
Access Attack
- An attempt to steal data typically for some type of financial gain.
*This topic will definitely be asked in the exam room, make note and have this stuff drilled in
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Posted by Josh Gahan
DHCP – Information That it Shares
May 14, 2013The following is a list of the information that a DHCP server will share with hosts.
- Host IP address
- Subnet Mask
- Default Gateway
- IP Address(es) of any DNS servers
Dynamic Host Control Protocol (DHCP)
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Fast Fact 1
May 12, 2013Routers break up broadcast domains.
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Posted by Josh Gahan
Point to Point and CPE
May 4, 2013
Key Terms:
CPE:
- Customer Premise Equipment
Dermarc:
- Demarcation Point, The point at which the telco does not own nor take responsibility for.
CSU/DSU:
- Channel service unite / data service unit
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Posted by Josh Gahan
Port Security
April 28, 2013Switches examine the source MAC address of the received frame, switches can take a few possible options if it discovers that the incoming MAC address on that port is NOT SECURE.
- shutdown (the switch shuts down the port and sends a log message and drops the frame/s , also the interface status will read err-disabled you have to run a no shutdown to open the port again) ON BY DEFAULT
- restrict (drops the frames and transmits a log message but does not shutdown the port)
- protect (only drops the frames)
When configuring Port security and the source MAC address is unknown switchport port-security mac-address sticky can be used and the switch will use the first mac address learned as the Secure MAC address
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Spanning Tree Protocol (STP)
April 27, 2013Switching loops form when multiple paths exist, when a frame is sent and the the frame travels between the switches and never ends up reaching it’s final destination.
STP is used to prevent switching loops and is on by default, it determines a loop free path and ports that are not on the path are put into a blocking mode. If the best path is no longer available STP will calculate a new “path” and ports on that path that where blocked are brought out of the blocking mode.
NB. the shortest physical path is not the best, STP looks at the speed of the links
STP Quick Overview
- On by default
- Used to prevent switching loops
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Posted by Josh Gahan
Introduction to VLANS
April 27, 2013A continuous generation of broadcasts on a network is called a broadcast storm, this will use the switches resources to the point of breakdown.
By default a switch is setup to use one broadcast domain, to mitigate this, creating more broadcast domains via creating new VLANS, Cisco switches are out of the box configured using VLAN1 named default.
Segmenting the networking by creating a new VLAN , only those hosts on the same VLAN will be able to communicate,connectivity to another VLAN is not possible without the implementation of a L3 device (eg Router)
Read more from Wikipedia on VLANS here
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CSMA/CD – Collision Sense Multiple Access / Collision Detection
April 25, 2013All you need to know about the CSMA/CD process
- Transmitting host will listen, if silent data transmission commences
- If a voltage change is observed, (this is the collision) both hosts will send a jam signal
- This starts a random backoff algorithm, and once the random time has elapsed the host will commence transmission again by listening to the wire.
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