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New Member

VLAN subnet

I am studying the cisco press book on BCMSN and I came across a question. When the describing about the characteristics of VLANs, the book says this, "A subnet must reside within one broadcast domain. This means that all stations residing in or ports configured on the same VLAN are assigned network address within the same subnet. However, a single VLAN can support multiple subnets" (page 27). Doesn't the last two sentences conflict each other?

3 REPLIES
Bronze

Re: VLAN subnet

A vlan will support devices in more than one subnet but devices will only be able to talk IP directly to devices configured on the same subnet. To reach devices on different subnets, you would require a router with secondary IP addresses configured on the VLAN.

New Member

Re: VLAN subnet

But Broadcast will be heard at all stations in the VLAN with differents subnets.

New Member

Re: VLAN subnet

Well Yuan.

A port that is configured as a trunk port has as many Spanning Tree instances enabled on it

as there are VLANs enabled on that particular trunk. Up to 1000 VLANs are allowed on a

Catalyst 5000 switch, but only up to 250 of those can be active on the local switch. This

means that if a switched internetwork contains up to 1000 VLANs, the Catalyst switches

will not have any problem. However, the collection of all the ports of each switch may not

be assigned to more than 250 of the internetwork’s VLANs. A port that is enabled (and has

Spanning Tree enabled on it), can be in one of Blocking, Listening, Learning, or

Forwarding states at a particular instance.

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