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Understanding Trunking Between Vlans on a Switch Better

GillverK
Level 1
Level 1

1.

cisco_new_question.JPG

 

2.

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So, I'm trying to understand trunking better. I was under the impression that if Trunk Ports were created, I could allow Vlan Traffic through from other VLANs, if they are "allowed" through the Trunks on each port. So, given the preceding topology, where each switch has VLANs 2, 3, and 4 and all are in the same subnet I was wondering why I couldn't successfully make any of the PC ping; they are attached to Trunk Ports? Do I absolutely have to have a router/L3 Switch for this? 

 

Thank you.

1 Accepted Solution

Accepted Solutions

luis_cordova
VIP Alumni
VIP Alumni

Hi @GillverK ,

 

When the packets arrive at a switch, they receive a tag, which associates them with a specific difussion domain(vlan).

By default this tag is 1.

Now, if you occupy several vlan, the packages will be tagged with those tags, so you can not communicate devices from different vlan.

Trunk links are used to allow the passage of packets with different tags, but not to achieve communication between them.

To achieve communication between vlan, you need a routing device, such as a router or an L3 switch.

 

Regards

 

View solution in original post

4 Replies 4

marce1000
VIP
VIP

 

 - ip routing and trunks are  in fact unrelated. Most people will map an IP subnet to a VLAN. But if you need comm between IP subnets you need a routing-solution somewhere.

 M.



-- Each morning when I wake up and look into the mirror I always say ' Why am I so brilliant ? '
    When the mirror will then always repond to me with ' The only thing that exceeds your brilliance is your beauty! '

Ah, I see. I wish the lessons I'm taking would stress this fact.

 

Thanks a lot.

luis_cordova
VIP Alumni
VIP Alumni

Hi @GillverK ,

 

When the packets arrive at a switch, they receive a tag, which associates them with a specific difussion domain(vlan).

By default this tag is 1.

Now, if you occupy several vlan, the packages will be tagged with those tags, so you can not communicate devices from different vlan.

Trunk links are used to allow the passage of packets with different tags, but not to achieve communication between them.

To achieve communication between vlan, you need a routing device, such as a router or an L3 switch.

 

Regards

 

Yes. This explains a lot. Than you.

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