ccna question

amir

Hí, I would to check out some thing with you, I wonder if you could clear this matter for me.

vlan uses:

ISL (cisco to cisco switches)


802.1Q (cisco to non-cisco switches)

STP uses:

Cisco (cisco to cisco switches)

802.1d (cisco to non-cisco switches)


Thank you

sikdogg

amir wrote:

vlan uses:

ISL (cisco to cisco switches)


802.1Q (cisco to non-cisco switches)

STP uses:

Cisco (cisco to cisco switches)

802.1d (cisco to non-cisco switches)

VLANs:

ISL and 802.1Q are standards used to differentiate VLANs when trunking. ISL is a Cisco proprietary standard that encapsulates the Ethernet frame adding 30 bytes to the total size.

802.1Q inserts VLAN info into the existing header (frame tagging) so as not to change the frame size.

VLANs & STP:

There are two methods for addressing/configuring STP with regard to VLANs, they are the Cisco and IEEE 802.1Q approach.

802.1Q uses the Common Spanning Tree (CST) method. With CST, one instance of STP runs for all VLANs.

Cisco's proprietary solution is Per-VLAN Spanning Tree (PVST) and Per-VLAN Spanning Tree Plus (PVST+). PVST is just as its name implies, an instance of STP runs for each VLAN. PVST+ adds the the ability to pass CST information into PVST. Both PVST and PVST+ require ISL.

I'm not absolutely sure about this but, I believe 802.1d is an STP standard that is used on transparent bridges and as such is not used in multi-VLAN environment. I would need to do some research to confirm this.

Webmaster

Here's a doc on 802.1d STP spec...

vman

thanks webmaster u allways provide us with the best