Allied Telesis AT-iMG634 - R2 Betriebsanweisung Seite 236

  • Herunterladen
  • Zu meinen Handbüchern hinzufügen
  • Drucken
  • Seite
    / 998
  • Inhaltsverzeichnis
  • LESEZEICHEN
  • Bewertet. / 5. Basierend auf Kundenbewertungen
Seitenansicht 235
VLAN Overview
iMG/RG Software Reference Manual (Switching)
2-86
To allow the frame to indicate the format of MAC Address information carried in MAC user data;
To allow VLANs to be supported across different MAC types.
Tagging a frame requires:
The addition of a tag header to the frame. This header is inserted immediately following the destination
MAC Address and source MAC Address fields of the frame to be transmitted;
Recomputation of the Frame Check Sequence (FCS).
When relaying a tagged frame between 802.3/Ethernet MACs, a switch may adjust the PAD field such that the
minimum size of a transmitted tagged frame is 68 octets.
FIGURE 2-2 Tagged frame format according to IEEE 802.3ac standard
The tag header carries the following information (see Figure 2-2):
The Tag Protocol Identifier (TPID) carrying an Ethernet Type value (802.1QTagType), which identifies the
frame as a tagged frame. The value of 802.1QTagType is 81-00
Preample
7 octets
Start frame delimiter
1 octet
1 0 0 0 0 0 0 1
0 0 0 0 0 0 0 0
6 octets
Source address
6 octets
Length/type = 802.1QTagType
2 octets
TAG control information
2 octets
MAC control length/type
2 octets
MAC client data
Pad
42-1500 octets
Frame check sequence
4 octets
User priority
VALN identifier VID (12 bit)
CFI
TAG header
Seitenansicht 235
1 2 ... 231 232 233 234 235 236 237 238 239 240 241 ... 997 998

Kommentare zu diesen Handbüchern

Keine Kommentare