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Webcast-Catalyst9k
New Member

2 Vlans Talking to each other

I am rookie when it comes to vlans so please keep this in mind.

What I am trying to accomplish is we have a 10.16.0.0/16 network.

I want to create 2 vlans (to seperate traffic)

like have 10.16.1.1-20 on 1 vlan and 10.16.1.21-40 on another, can I do this and have them talk to each other and accomplish seperate broadcast domains with the vlan?

Thanks again

6 REPLIES
New Member

Re: 2 Vlans Talking to each other

if you use vlans then you will need to route between

them.

for 20 hosts per vlan use 27 bit mask 255.255.255.224 this will divide your addresses into

0-31 32-63 etc

New Member

Re: 2 Vlans Talking to each other

So I have to put a router in between them? Can I use 1 interface with a primary and secondary address?

New Member

Re: 2 Vlans Talking to each other

Yes this will work only if the router that you are using supports trunking.

-Henry

New Member

Re: 2 Vlans Talking to each other

Hi,

I noticed your conversation and in response I would like to ask if a Cisco 2500 running 11.2 os supports trunking?

Regards

Adrian

mailto : adrian@shortwave-it.co.uk

New Member

Re: 2 Vlans Talking to each other

Ok

1. It seems like the 10.16.1.1-20 and the 10.16.1.21-40 fall within the same 255.255.0.0 IP subnet. In this case saparating these ip addresses with a vlan would totally isolate isolate the machines from one another.

vlan 1 10 .16 .1. 1-20

vlan 2 10 .16 .1. 21-40

255.255.0. 0

these are the same ip subnet.

2. If you meant the subnet 10.16.0.1-20 and

10.17.0.1-20 then they would be seperate broadcast domains but unable to talk to one another without a layer 3 interface for routing. So the answer is no you still wouldnt have full connectivity.

Lemme know if this helps

Sincerely,

Paul Aquino

CSE

Cisco Systems

New Member

Re: 2 Vlans Talking to each other

I have done something similar to this, but not exactly what you are looking at.

I use Bay Networks Baystack 350T switches to seperate my vlans behind the router. Normally, I only vlan seperate subnets, but it should also work for vlans inside a subnet. We use this to run a single line into a building and seperate the tenant traffic via vlans to a single interface on a cisco router. I have never gotten a cisco catalyst switch to do the same thing I have seen with Baystack switches. I am not sure if this is because of functionality or inexperience on my part with catalyst switches (probably the latter of the two.)

I would NOT recommend taking this path however. If you want to seperate the 2 networks, I would recommend routing the two segments of the network between two interfaces on a router in two seperate networks. I just believe in presenting all options ;c)

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