Question about InterVlan Routing

Answered Question
Mar 8th, 2008
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Hello,


Iam a beginer in intervlan routing, and i need your help ^^.


There is my network : http://img398.imageshack.us/my.php?image=vlansrs9.jpg


I need 4 vlans on both switches, and different numbers of host for eaches.


I have configured Vtp on the both switches, subinterfaces on R2 and R1 for eaches Vlans but my probleme is with S2.

He don't have a router directly connected, so i don't know how to make the inter vlan routing for him.

Sorry for my realy bad english and by advance, thanks.


Clemmentine


Correct Answer by sundar.palaniappan about 9 years 3 weeks ago

Assign the switchport(s) connected to each user to the appropriate VLAN using the syntax 'switchport access vlan (#)'. As I stated in my earlier post configure the link between the switches as a trunk. Since you already had configured VTP all 4 VLANs should have been dynamically propogated to all three switches.


HTH


Sundar

Correct Answer by glen.grant about 9 years 3 weeks ago

As previous poster said all that is needed is to make sure the links between the switches are all trunks with the required vlans allowed across those trunk links and the layer 3 definitions for any vlan you need routed defined under subinterfaces on the routers .

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sundar.palaniappan Sat, 03/08/2008 - 22:16
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Clemmentine,


S2 need not be directly connected to any router to be able to route traffic between VLANs for users connected to S2. Configure the link between all 3 switches and the link to both routers as trunk ports. Make sure all the VLANs are propogated to all 3 switches, including S2 via VTP. Configure sub-interfaces (VLAN interfaces) for all the VLANs you have configured in one or both routers to forward traffic between VLANs that exist in your setup.


HTH


Sundar

Correct Answer
glen.grant Sun, 03/09/2008 - 05:20
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As previous poster said all that is needed is to make sure the links between the switches are all trunks with the required vlans allowed across those trunk links and the layer 3 definitions for any vlan you need routed defined under subinterfaces on the routers .

Clemmentine Sun, 03/09/2008 - 11:59
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Thanks you for the informations, but i have one more question, i think i don't understand somethink.


We are ok that on S1 S2 S3 i will have 4 vlans, Vlan 1 2 3 and 4.

For each vlans i need one subnets adress, so i need 12 subnets in total.


On the routers, i need one subinterfaces for eaches subnets.

For exemple:


R1 interface s0.1

encapsulation dot1q 1

ip add for vlan 1 on S1


R2 interface s0.1

encapsulation dot1q 1

ip add for vlan 1 on S2


Now my problem, what i have to do for the vlan 1 on S3, i can't creat another subinterface with the encap dot1q 1.


I hope you understand what's my problem.

Again sorry for the bad english and tyvm.


Clem.

sundar.palaniappan Sun, 03/09/2008 - 13:23
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You just need one IP subnet per VLAN. A VLAN can span multiple switches but it still part of the same broadcast domain/IP Subnet. As such you won't need a separte sub-interface on the router for every switch. Configure 4 sub-interfaces on the router(s) and assign the corresponding VLAN IP address to the interfaces. The address configured on the router sub-interface(s) would be the default gateway address for the users on the respective VLANs.


HTH


Sundar

Clemmentine Sun, 03/09/2008 - 17:11
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Ok i've understand.

I just have a last question. I need different numbers of host for eaches switches ( S1 12 hosts, S2 24 hosts etc etc ).

Can you told me what i have to do ?

Correct Answer
sundar.palaniappan Mon, 03/10/2008 - 11:26
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Assign the switchport(s) connected to each user to the appropriate VLAN using the syntax 'switchport access vlan (#)'. As I stated in my earlier post configure the link between the switches as a trunk. Since you already had configured VTP all 4 VLANs should have been dynamically propogated to all three switches.


HTH


Sundar

Clemmentine Mon, 03/10/2008 - 15:34
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Hello,


Just a big thanks, everything is clear now for me.

Tyvm for the answers.


Clem

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