Lucent Technologies P550 - Manual (Page 43)

Overview of the P220 Gigabit Switch Family
Cajun P550/P220 Switch Operation Guide 2 -7
Figure 2-3. Trunking Translation
Dual Layer Spanning Trees
Spanning trees are an IEEE 802.1 standard which provides distributed routing over
multiple LANs connected by bridges.
There are three spanning tree models:
❒ Single IEEE 802.1D spanning tree
❒ Spanning tree per VLAN
❒ Optimized “per-VLAN” spanning trees using a scalable, two-layer spanning tree
approach
Note: All models interoperate with legacy IEEE 802.1D bridges and switches.
Dual layer spanning trees provide two very important capabilities:
❒ Smaller spanning tree domains means much faster convergence during spanning
tree reconfiguration.
❒ Per-VLAN operation enables you to use more of the available bandwidth when you
have redundant links. A particular link can be blocked on one VLAN, but still
forward packets on another.
Frame
Format:
•“Clear”
•IEEE
802.1Q
•Multilayer
•3Com
Translation Function Translation Function
Frame Format:
“Normal” - Ethernet
or 802.3 with valid
CRC
Trunking Translation:
Frame
Format:
•“Clear”
•IEEE
802.1Q
•Multilayer
•3Com