Vlan Tagging

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Apr 7th, 2007
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I have several 2950 switches that I need to enable vlans on. I have dedicated ethernet connections between two switch (from one NOC co-lo, to another NOC co-lo). I want to setup vlans on the connected switch ports on this ethernet link, but I do not want to setup vlans on my routers that are connected to each switch. For example: Port 1 on each switch would be a simple trunk allowing the vlans I define in the trunk to pass traffic. Next, I'll have port 2 on each switch defined as members of the same vlan, but they will be passing traffic between each other over port 1's trunk. I basically need assistnace on the proper vlan configuration. I do not want the vlans I define to be able to communicate with each other.

Can someone help me get started with this?



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Amit Singh Sat, 04/07/2007 - 10:24
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If you want only Layer2 traffic to travelled across the links between the 2 switches, then just create vlans and trunks accross both the switches. Do not create any trunk on the router and sub-interfaces on it for inter-vlan routing.2950 switches are pure layer2 switches and if you dont create inter-vlan routing on your routers all the vlans will be pure layer 2 and will not be able to talk to each other.

-amit singh

Jesse Hottle Mon, 04/09/2007 - 06:16
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What is I wanted to create the IVL using a router too. Can you help me with a sample config to make this work? Also, I need to be able to use ip-helper for dhcp for some clients that would be on subnets assoicted with sub-interfaces on the routers.

Amit Singh Mon, 04/09/2007 - 09:51
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You can use one of your router to do the inter-vlan routing for you by creating the router on stick model. Make sure that you hav ethe encapuslation support on the router interfaces and you need atleast "IP PLUS" featureset on the router for that. Please see the link below for sample configuration for IVL and DHCP configuration on the router:



Please make sure that when defining the DHCP pools for the subnet " default-router" should be the sub-interface ip and the same will be the gateway on your hosts.

HTH,Please rate if it does.

-amit singh


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