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Connect Two Buildings Different Subnets

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Ty Kolff
Occasional Visitor

Connect Two Buildings Different Subnets

I have two schools that are on different subnets. The main location has a ProCurve 5412zl and is on the subnet 172.20.0.0/16, the second remote school has a ProCurve 3500yl and is on the subnet 172.21.0.0/16. I recently connected the two buildings via a wireless bridge. The remote school needs to connect to the main site to communicate with Servers and connect to the Internet. I have attempted to setup VLANS between the two switches and enabled ip routing, however they are still unable to communicate.

What is the proper way to configure this link and enable routing between the two subnets/locations?

Thank You.
7 REPLIES
Olaf Borowski
Respected Contributor
Solution

Re: Connect Two Buildings Different Subnets

Ty,

The wireless bridge is your 3rd subnet. Configure a seperate vlan on each of the switches (example VLAN 999) and assign and IP address to each side with a /30. Enable IP routing and add static routes.
On 35xx (vlan 999): IP = 192.168.1.1/30
on 54xx (vlan 999): IP = 192.168.1.2/30

On 35xx: ip route 0.0.0.0/0 192.168.1.2
which routes all traffic that is not local to the main site.
On 54xx: ip route 172.21.0.0/16 192.168.1.1

That assumes that the wireless bridges ethernet port are connected to VLAN 999 on each side.

Good luck,

Olaf
Ty Kolff
Occasional Visitor

Re: Connect Two Buildings Different Subnets

Olaf,

Thank You. That seems to be working great! I had RIP enabled and I think that was messing things up. One other quick question. Do I need to set the default gateway on client computers to the ip address of the 3500 switch?

Thanks,

Ty
Ty Kolff
Occasional Visitor

Re: Connect Two Buildings Different Subnets

One other issue I have now is that when I attempt to ping an internal address, say 172.20.0.1 at the main site it works just fine, however when I ping say 74.125.95.104 it comes back with "Destination port unreachable."
Olaf Borowski
Respected Contributor

Re: Connect Two Buildings Different Subnets

Ty,

Yes, you do. The default gateway for the 172.21.0.0/16 network should be the IP address of the VLAN on the switch (something with 172.21.x.x).

Regarding your second question: You need to do the same thing for the 172.20.x.x network. Configure the clients to point to the IP address of the VLAN they are in as their default gateway. To get to an external network, you need a static route to your Internet router or firewall and you also need to tell the router/firewall about the networks that the 54xx and 35xx have attached. Two static routes on the router/firewall: ip route 172.20.0.0/16
2nd route: ip route 172.21.0.0/16 .

Olaf
Ty Kolff
Occasional Visitor

Re: Connect Two Buildings Different Subnets

Olaf,

Thank you very much for your assistance. Everything is working great now.

Ty
Ty Kolff
Occasional Visitor

Re: Connect Two Buildings Different Subnets

The solution above worked perfectly.
tanu47
Occasional Visitor

Re: Connect Two Buildings Different Subnets

Hi,

Need to know that is that possible to connect two building through one subnet?

Or have to need of two subnet for connecting?

http://www.groupsmsindia.com/