BigIron RX Series Configuration Guide
333
53-1001810-01
PVST/PVST+ compatibility
12
Overview of PVST and PVST+
Per VLAN Spanning Tree (PVST)
is a Cisco proprietary protocol that allows a Cisco device to have
multiple spanning trees. The Cisco device can interoperate with spanning trees on other PVST
devices but cannot interoperate with IEEE 802.1Q devices. An IEEE 802.1Q device has all its ports
running a single spanning tree.
PVST+
is an extension of PVST that allows a Cisco device to also
interoperate with devices that are running a single spanning tree (IEEE 802.1Q).
The PVST+ support allows the device to interoperate with PVST spanning trees and the IEEE
802.1Q spanning tree at the same time.
IEEE 802.1Q and PVST regions cannot interoperate directly but can interoperate indirectly through
PVST+ regions. PVST BPDUs are tunneled through 802.1Q regions, while PVST BPDUs for VLAN 1
(the IEEE 802.1Q VLAN) are processed by PVST+ regions.
Figure 31
shows the interaction of IEEE
802.1Q, PVST, and PVST+ regions.
FIGURE 31
Interaction of IEEE 802.1Q, PVST, and PVST+ regions
VLAN tags and dual mode
To support the IEEE 802.1Q (Common Spanning Tree) portion of PVST+, a port must be a member
of VLAN 1. Cisco devices always use VLAN 1 to support the IEEE 802.1Q portion of PVST+.
For the port to also support the other VLANs (the PVST+ VLANs) in tagged mode. The port must be
a dual-mode port.
The untagged frames are supported on the port’s
native VLAN
. By default, the native VLAN is the
same as the device’s
default VLAN
1
, which by default is VLAN 1. Thus, to support IEEE 802.1Q in a
typical configuration, the port must be able to send and receive untagged frames for VLAN 1 and
tagged frames for the other VLANs.
1.
Cisco PVST/PVST+ documentation refers to the Default VLAN as the
Default Native VLAN
.
PVST+Region
IEEE 802.1Q Region
PVST+Region
PVST Region
PVST BPDUs
(over ISL trunks)
PVST BPDUs
(over ISL trunks)
Do not
connect
dual mode
port
dual mode
port
802.1D BPDUs
802.1D BPDUs
PVST BPDUs tunneled through
the IEEE 802.1Q region
Summary of Contents for Brocade DCX
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Page 88: ...16 BigIron RX Series Configuration Guide 53 1001810 01 Searching and filtering output 1 ...
Page 300: ...228 BigIron RX Series Configuration Guide 53 1001810 01 Displaying IP information 7 ...
Page 318: ...246 BigIron RX Series Configuration Guide 53 1001810 01 Deploying a LAG 8 ...
Page 418: ...346 BigIron RX Series Configuration Guide 53 1001810 01 SuperSpan 12 ...
Page 482: ...410 BigIron RX Series Configuration Guide 53 1001810 01 MRP CLI example 14 ...
Page 506: ...434 BigIron RX Series Configuration Guide 53 1001810 01 Displaying VSRP information 15 ...
Page 582: ...510 BigIron RX Series Configuration Guide 53 1001810 01 Viewing Layer 2 ACLs 20 ...
Page 634: ...562 BigIron RX Series Configuration Guide 53 1001810 01 Troubleshooting ACLs 21 ...
Page 642: ...570 BigIron RX Series Configuration Guide 53 1001810 01 Trunk formation 22 ...
Page 746: ...674 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIP filters 24 ...
Page 808: ...736 BigIron RX Series Configuration Guide 53 1001810 01 Displaying OSPF information 25 ...
Page 938: ...866 BigIron RX Series Configuration Guide 53 1001810 01 Displaying MBGP information 27 ...
Page 950: ...878 BigIron RX Series Configuration Guide 53 1001810 01 Using secure copy 28 ...
Page 988: ...916 BigIron RX Series Configuration Guide 53 1001810 01 Clearing IS IS information 29 ...
Page 1054: ...982 BigIron RX Series Configuration Guide 53 1001810 01 Sample 802 1x configurations 33 ...
Page 1108: ...1036 BigIron RX Series Configuration Guide 53 1001810 01 sFlow 39 ...
Page 1190: ...1118 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIPng information 44 ...
Page 1270: ...1198 BigIron RX Series Configuration Guide 53 1001810 01 Displaying ACLs 47 ...
Page 1310: ...1238 BigIron RX Series Configuration Guide 53 1001810 01 Displaying OSPFv3 information 48 ...
Page 1382: ...1310 BigIron RX Series Configuration Guide 53 1001810 01 Commands That Require a Reload D ...
Page 1435: ...BigIron RX Series Configuration Guide 1363 53 1001810 01 VSRP E ...
Page 1436: ...1364 BigIron RX Series Configuration Guide 53 1001810 01 VSRP E ...