How to vlans on Cisco 1861 router / switch

[d_alva]

Equipment in use:
Cisco 1861 router – located at remote site
Cisco 3750 switch – located at headquarter site

Background:
We have some experience with vlans, routing, switches etc.
Prior to this new setup we were using the 1861 with T1 serial cards and linked back to headquarters to a Cisco 6509
switch. Now we are replacing the T1 link with the AT&T Ethernet service and using vlans to keep the remote subnets in
place.

We wish to do the following:
Allow desktops on Vlan 35(remote) to access servers on vlan 1(headquarter)
On Cisco 1861 setup a Vlan 35 for the desktops to use at the remote site.
On Cisco 3750 use the default Vlan 1 for servers located at headquarters.

Connectivity between the 1861 and 3750 is an Ethernet link provided by AT&T.
On 3750, AT&T Ethernet service will be plugged into port 1.
On 1861, not clear which port to plug Ethernet service into. We understand to route desktop from vlan 35 to servers on
vlan 1 requires a router. The 1861 is a combo switch/router which we anticipate will be the router used.

Questions:
Which port on 1861 do we connect the AT&T service into? Recall the other end of this “cable” will be going to the 3750
port 1.
On which device do the vlans get defined?
What is example IP address schema required to allow data to flow from desktop to servers?
Other comments/suggestions would be appreciated.

[Georg Pauwen]

Hello,

--> Connectivity between the 1861 and 3750 is an Ethernet link provided by AT&T.

This is the crucial piece of information: is this a layer 2 or a layer 3 link ? The answer on how to configure your 1861 depends on that. 

[d_alva]

I believe it is a layer 2 because this same link at the headquarter is shared out to multiple sites (one to many) and I believe AT&T said we will need to use vlans to all the sites.  Does a layer 3 allow deployment of one to many?

[d_alva]

If Layer 3 does allow a one to many deployment then I will need to confirm with AT&T which it is.

[balaji.bandi]

thank you for the input, you mean you have One Ethernet  Layer 2 connection and you have many branches deliverer Layer 2? how many sites, how many ethernet cables are they delivering at the main office?

My understanding you replacing all serial with Ethernet service? how is your old setup serial connections ? from branches to head office?

[d_alva]

About a dozen sites eventually.  Only 1 cable delivered at main site.

The old setup was T1 from sites to one T3 at main site.  We are slowly moving away from that.

I am going to double check with AT&T to confirm it is a Level 2 service.

[d_alva]

We have confirmed it is an AT&T Switched Ethernet (ASE) Level 2 circuit.

[paul driver]

Hello

Can you post a topology diagram of your current and intended setup of the network in relation to the spoke and HQ sites please.

[d_alva]

Here is a simple topo showing before and after.  Not sure if this gives the information you were looking for.

[d_alva · Accepted solution]

Solution was to not use any Vlans.  Instead just replace the T1 link with a Router link from port F0/0 on the 1861 to a router port on the main switch.  Each site uses a unique IP on the F0/0 port but links to the common router port on the main switch with the single IP.