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Sunday, October 2, 2011

How do you connect catalyst 3750 to Procurve 2910


If the connecting port on 3750 to procurve 2910 belongs vlan 10, does the connecting port on procurve 2910 has to belong to the same vlan?

Would both switches be connected if their connecting ports do not have the same vlan number? Do both connecting ports have to be tagged or untagged or does not matter?

In general, without being vendor-specific, if you are interconnecting two switches, they should be conected by ports that are either both placed into the same and single untagged VLAN only (we call them access ports), or they are members of the same set of VLANs (we call them trunk ports in Cisco parlance).

Connecting two access ports that belong to different untagged VLANs on each switch is incorrect. That would make the two VLANs leak into each other and effectively merge.

Also, connecting an access port on one switch with a trunk port on another switch is incorrect. A trunk ports expects to be able to carry data from multiple VLANs, while the access port is capable of carrying a single VLAN only. This would lead to connectivity issues.

Tagging mode must be identical on both ends of the link - the set of tagged and untagged (native VLANs) should be identical.

Interconnect switches using trunks unless there is a particular special need to have the neighboring switch as a whole placed into a single VLAN only. This would mean that the configuration on the Cisco port would be:

interface Fa0/1
switchport trunk encapsulation dot1q ! Not necessary/supported on many switches
switchport mode trunk
switchport trunk native vlan 1


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