KB.15.15

Figure 200 Example of correct VLAN port assignments on a link

• If VLAN_1 (VID=1) is configured as "Untagged" on port 3 on switch "X," it must also be

configured as "Untagged" on port 7 on switch "Y." Make sure that the VLAN ID (VID) is the

same on both switches.

• Similarly, if VLAN_2 (VID=2) is configured as "Tagged" on the link port on switch "A," it must

also be configured as "Tagged" on the link port on switch "B." Make sure that the VLAN ID

(VID) is the same on both switches.

Duplicate MAC addresses across VLANs

The switches operate with multiple forwarding databases. Thus, duplicate MAC addresses occurring

on different VLANs can appear where a device having one MAC address is a member of more

than one 802.1Q VLAN, and the switch port to which the device is linked is using VLANs (instead

of MSTP or trunking) to establish redundant links to another switch. If the other device sends traffic

over multiple VLANs, its MAC address consistently appears in multiple VLANs on the switch port

to which it is linked.

Be aware that attempting to create redundant paths through the use of VLANs causes problems

with some switches. One symptom is that a duplicate MAC address appears in the Port Address

Table of one port and then later appears on another port. While the switches have multiple

forwarding databases and thus do not have this problem, some switches with a single forwarding

database for all VLANs may produce the impression that a connected device is moving among

ports because packets with the same MAC address but different VLANs are received on different

ports. You can avoid this problem by creating redundant paths using port trunks or spanning tree.

Figure 201 Example of duplicate MAC address

Fan failure

When two or more fans fail, a two-minute timer starts. After two minutes, the switch is powered

down and must be rebooted to restart it. This protects the switch from possible overheating.

HP recommends that you replace a failed fan tray assembly within one minute of removing it.

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