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New Member

Catalyst 3560X compliance with 802.3ac

Hi,

I know there shouldn’t be a problem as Cisco Catalyst Switchs are compliant with IEEE 802.3ac, but i don't find that in any document.

Can you please tell me where to find a such information ??

Thank you,


  • LAN Switching and Routing
2 REPLIES
VIP Super Bronze

Catalyst 3560X compliance with 802.3ac

Hi,

Here is doc you can look at:

the 802.3ac standard, that is, the addition of the four octets after the source MAC address. Their presence is indicated by a particular value of the EtherType field (called TPID), which has been fixed to be equal to 0x8100. When a frame has the EtherType equal to 0x8100, this frame carries the tag IEEE 802.1Q/802.1p. The tag is stored in the following two octets and it contains 3 bits of user priority, 1 bit of Canonical Format Identifier (CFI), and 12 bits of VLAN ID (VID). The 3 bits of user priority are used by the 802.1p standard; the CFI is used for compatibility reasons between Ethernet-type networks and Token Ring-type networks. The VID is the identification of the VLAN, which is basically used by the 802.1Q standard; being on 12 bits, it allows the identification of 4096 VLANs.

Link:

http://www.cisco.com/en/US/docs/ios/12_2/switch/configuration/guide/xcfvl.html

HTH

New Member

Catalyst 3560X compliance with 802.3ac

Thank you,

So, if i understood correctly, 802.3ac is a scheme for the ethernet frame, that places an additional 4 bytes after src MAC, for VLAN tagging and priority purposes (that takes the ethernet frame size from 1518 bytes to 1522). Cisco respects that standard (IEEE 802.3ac) by implementing the mechanism mentionned above, which includes either 802.1q information and 802.1p information.

Am i missing something or is it ok ?

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