Implementing Dell PowerConnect 5316M switches
Two examples can help administrators understand how to implement
advanced configuration options for PowerConnect 5316M switches: one
for MSTP and one for QoS.
example mstP implementation
Administrators can use MSTP with PowerConnect 5316M switches to
enable load balancing for a blade server chassis. Figure 5 shows a typical
high-availability implementation using two PowerConnect 5316M chassis
switches along with two external PowerConnect 5324 switches that provide
redundancy and availability in case of a switch failure. MSTP is used to
balance the blade traffic from the PowerConnect 5316M switches to the
two PowerConnect 5324 switches.
For example purposes, assume that the network includes VLANs 2–7,
with VLANs 2–4 assigned to MSTP instance 1 and VLANs 5–7 assigned to
MSTP instance 2. Link aggregation between the PowerConnect 5316M
and PowerConnect 5324 switches groups together multiple links and
helps provide load balancing and fault tolerance. (These configuration
examples still apply when using individual physical interfaces rather
than LAGs.)
To simplify the example, consider the connectivity of only the
PowerConnect 5316M switch shown in the lower right corner of Figure 5.
The cost and priority settings for this switch’s LAG 1 and LAG 2 interfaces
can be adjusted separately for MSTP instances 1 and 2 to set the LAG port
roles and states shown in Figure 6. These port roles and states are defined
in the RSTP standard; the root port provides the lowest cost when the
switch forwards packets to the root switch and would be in the forwarding
state, while the alternate port offers a different path to the root switch
and would be in the discarding state. Figures 7 and 8 show the resulting
topologies for the two MSTP instances.
If this network had used traditional STP, only one of the LAGs would
carry traffic for all the VLANs. Because MSTP allows multiple forwarding
paths for data traffic, the network can maintain separate logical topolo-
gies for different VLAN groups to help make efficient use of network
resources. A similar setup can also be used with the other PowerConnect
5316M switch.
4
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G1
G2
Layer � switch
Dell PowerConnect ����
Dell PowerConnect ����
Dell PowerConnect ����M
Dell PowerConnect ����M
LAG �
LAG �
LAG �
LAG �
Figure 5.
Example high-availability MSTP implementation using Dell
PowerConnect 5316M and PowerConnect 5324 switches
G1
G2
Layer � switch
Dell PowerConnect ����
Dell PowerConnect ����
Dell PowerConnect ����M
LAG �
Discarding
LAG �
Forwarding
VLANs �–�
Figure 8.
Network topology for MSTP instance 2 in the example high-
availability MSTP implementation
G1
G2
Layer � switch
Dell PowerConnect ����
Dell PowerConnect ����
Dell PowerConnect ����M
LAG �
VLANs �–�
Forwarding
LAG �
Discarding
Figure 7.
Network topology for MSTP instance 1 in the example high-
availability MSTP implementation
mstP instance
VLans
LaG 1 role
LaG 1 state
LaG 2 role
LaG 2 state
1
2–4
root
Forwarding
alternate
discarding
2
5–7
alternate
discarding
root
Forwarding
Figure 6.
LAG port roles and states for a Dell PowerConnect 5316M switch in the example MSTP implementation
reprinted from
Dell Power Solutions,
May 2007. Copyright © 2007 dell inc. all rights reserved.
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