Inter-VLAN

Answered Question
May 29th, 2007
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Hi Experts,


My uploaded topology has one switch with two VLANs Marketing,Finance and has two connections to the routers ( not seen in the picture) , one for each VLAN ...


So... I configured that topology with my Virtual Lab with Two TrunkLinks between the switch and the two ports of the router and they didn't work.. why???!!!


I think that those links should be TrunkLinks not AccessLinks... Right ?


Regards,

Ibrahim Alwahidi




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Correct Answer by mohammedmahmoud about 9 years 10 months ago

Hi Ibrahim,


Inter-VLAN routing using an external router can be done in 2 ways in your case, either having 2 access interfaces on the router each belonging to one of the 2 VLANs on the switch and thus the inter-VLAN routing is done by routing the traffic between the 2 interfaces on the router.


The second solution is the router-on-a-stick, this solution reduces the need of multiple interfaces on the router, and thus by making the interface trunk and using subinterfaces each in a VLAN and thus the routing is done between sub-interfaces, which is the preferred solution as it reduces the interfaces required on the router doing the inter-VLAN routing.


I hope that i've been informative.



HTH, please do rate all helpful replies,

Mohammed Mahmoud.

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rais Tue, 05/29/2007 - 08:59
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You can configure one port on the router to be 802.1Q trunk with ether sub-interfaces. The corresponding port on switch would also need to be trunk.


Thanks.

alwahidi22 Tue, 05/29/2007 - 09:08
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Thank you Sir,


I know that i can make one router interface to make Inter-Vlan but i want to make two ports so what should be TrunkLink or AccessLink ?


Regards,

Ibrahim Alwahidi

Paolo Bevilacqua Tue, 05/29/2007 - 09:00
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Hi,


When switch connects to router with one link for inter-vlan routing, it must be trunk.

When switch connects to router with more than one link, it can also be access, however in this case you will need one link per vlan.


Hope this helps, please rate post if it does!

Correct Answer
mohammedmahmoud Tue, 05/29/2007 - 09:57
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Hi Ibrahim,


Inter-VLAN routing using an external router can be done in 2 ways in your case, either having 2 access interfaces on the router each belonging to one of the 2 VLANs on the switch and thus the inter-VLAN routing is done by routing the traffic between the 2 interfaces on the router.


The second solution is the router-on-a-stick, this solution reduces the need of multiple interfaces on the router, and thus by making the interface trunk and using subinterfaces each in a VLAN and thus the routing is done between sub-interfaces, which is the preferred solution as it reduces the interfaces required on the router doing the inter-VLAN routing.


I hope that i've been informative.



HTH, please do rate all helpful replies,

Mohammed Mahmoud.

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