Archive for November, 2007

Switchport Configurations Explained

Filed in CCIE, Switching by on November 27, 2007 6 Comments
Switchport Configurations Explained

It always helps me to think of the English translation when trying to memorize and understand some the Cisco IOS settings I think are important. Here are some Cisco IOS switchport configurations translated into English: ‘switchport mode trunk‘ says: “Always trunk on this end, and I will send DTP to attempt to negotiate a trunk […]

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VLAN Trunking using IEEE 802.1Q

Filed in CCIE, Switching by on November 27, 2007 1 Comment
VLAN Trunking using IEEE 802.1Q

IEEE 802.1Q (sometimes referred to as 1Q or DOT1Q) is a industry standards based implementation of carring traffic for multiple VLANs on a single trunking interface between two Ethernet switches. 802.1Q is for Ethernet networks only. Unlike ISL , 802.1Q does not encapsulate the original Ethernet frame. For Ethernet V2 frames, 802.1Q inserts a new […]

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VLAN Trunking using ISL

Filed in CCIE, Switching by on November 26, 2007 3 Comments
VLAN Trunking using ISL

Inter-Switch Link (ISL) is a Cisco specific implementation of trunking multiple VLANs between two Cisco switches where a single interface will carry traffic for more than one VLAN. ISL was designed to work with Ethernet, FDDI, Token Ring, and ATM. ISL completely encapsulates the original Ethernet frame by adding a new 26 byte header and […]

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Things to know about VTP

Filed in CCIE, Switching by on November 21, 2007 2 Comments
Things to know about VTP

Some notes about VTP (VLAN Trunking Protocol): Cisco switches running Cisco IOS store VTP and VLAN information in a separate database stored in Flash, in file called vlan.dat. Cisco switches running CatOS store VTP and VLAN information in the main switch configuration file, stored in NVRAM. VTP information is only transmitted over trunk ports. A […]

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Identifying Ethernet Multicast

Filed in CCIE, Switching by on November 21, 2007 13 Comments
Identifying Ethernet Multicast

Just like there are 3 different Ethernet header types, there are also 3 different types of Ethernet addresses: Unicast Broadcast Multicast A unicast frame contains the unique MAC address of the destination receiver. A broadcast frame contains all binary 1′s as the destination address (FFFF.FFFF.FFFF). A multicast frame contains the unique multicast MAC address of […]

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Identifying Ethernet Header Types

Filed in CCIE, Switching by on November 19, 2007 4 Comments
Identifying Ethernet Header Types

There are 3 different Ethernet Header types defined by the IEEE and in use today. So, one question comes to mind: When a Ethernet receiver receives a frame, how does it know what kind of header it is? After all, if a receiver is unable to properly recognize the header type, it will not be […]

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