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Webcast-Catalyst9k
New Member

Share port between 2 VLANs

I am thinking about seperation the switch into 2 VLANs, however there is only one ethernet port to connect between the switch and the router. So only 1 VLAN can have connection to the router (i.e, internet connection). What can I do to allow both VLANs to have internet connection? Please assist me

Thankyou

8 REPLIES
New Member

Re: Share port between 2 VLANs

If both your router and switch support either 802.1q or ISL trunking, you can use a single switch port to the router for both vlans.

Mick.

New Member

Re: Share port between 2 VLANs

Thanks for your reply. But can you say a little bit more into detail about how to do it?

From my knowledge we should seperate the ports into 2 groups, so vlan doesnt the port connected to the router belongs to?

New Member

Re: Share port between 2 VLANs

I'd be happy to help, but I have no idea what hardware you're running.

If you configure the switch to trunk all of its vlans over a single port, and configure the router (if Cisco) with sub-interfaces using "encapsulation isl" or "dot1q", each sub-interface would be a logical interface to each vlan.

Mick.

New Member

Re: Share port between 2 VLANs

could u list the commands to configure the subinterface on.. lets say.. an E0 port. Thanks

New Member

Re: Share port between 2 VLANs

I believe you need to use FastEthernet to configure trunking support.

interface FastEthernet 0/0

no ip address

!

interface FastEthernet 0/0.1

encapsulation isl 1 (vlan 1)

ip address 10.1.1.1 255.255.255.0

!

interface FastEthernet 0/0.2

encapsulation isl 100 (vlan 100)

ip address 10.100.1.1 255.255.255.0

!

The "(vlan 1)" and "(vlan 100)" are not to be typed... just being clear. ;)

Mick.

New Member

Re: Share port between 2 VLANs

Cheers Mick! I'll give it a whirl :-)

New Member

Re: Share port between 2 VLANs

Mick,

If I remember correctly (I was only superficially involved) we had some problems when we wanted to do the exact same thing for our AAVID install at our office when we put in our IP PBX. When we attempted to configure the sub-interfaces on the ethernet interface, we had major issues with the data flow. We were forced to install a second interface to allow both voice and data to route via the 3640 we were using at the office.

I don't know that the issue has not been addressed, but this was as of 4 to 6 months ago.

Mike

New Member

Re: Share port between 2 VLANs

You need enable trunk in b/w switch and router with dot1Q or ISL encapsulation . Then you should be able to send 2 vlans across .

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