Re: Help configuring Point-To-Point T1

On Sep 19, 12:32 am, "jlama...@xxxxxxxxx" <jlama...@xxxxxxxxx> wrote:
On Sep 18, 8:28 pm, Oliver Garraux <olrben...@xxxxxxxxx> wrote:



On Sep 18, 9:13 pm, "jlama...@xxxxxxxxx" <jlama...@xxxxxxxxx> wrote:

Hi,
I have a point-to-point T1 (private line) between 2 offices.
I have Cisco 3560 switches at both locations.
At one location I have an external CSU/DSU, and at the other location
I have a Cisco 2851 with a CSU/DSU port free on the WIC card.

My intention was to trunk the 2 Cisco 3560s together over the T1,
however I'm confused as to how to configure the serial interface on
the 2851 to pass-through to the 3560.

Thanks.

I'm kind of confused on exactly what your situation is.

How are you connecting the 3560 to the external CSU/DSU? Do you have
a router there too?

Are you wanting to create a VLAN trunk between the two switches? So
that you could have a VLAN that spans across both offices? If so,
then, I don't think you can really do that. A 802.1q VLAN trunk uses
taking in the Ethernet header to identify which VLAN a packet belongs
on. The Ethernet headers would be dropped before it goes onto the T1
serial link, because the T1 line does not use Ethernet as a L2
protocol - it uses PPP/HDLC/etc. You also wouldn't really want to
have the VLAN going over the WAN because all of the broadcasts on that
network would be needlessly forwarded over the WAN wasting bandwidth
on the relatively low-bandwidth WAN connection.

You could certainly have VLAN's set up on both sides of the WAN, and
use the routers to route between them, but each VLAN would only exist
on one side of the WAN.

Sorry if I misunderstood your question.

Ok, here's my situation (with hopefully gorey enough details).
Office 1 (current) :
1700 series router (1 WIC port) w/ Internet T1
Bunch of servers (staying put)
VOIP PBX (staying put) w/ Voice T1
Currently unused Adtran CSU/DSU
3560 Switch
A couple PCs

Office 2 (new):
2851 Router (2 VWIC ports) w/ Internet T1
3560 Switch
Bunch of PCs that need server access to the servers at Office 1
Phones that need access to the VOIP PBX at Office 1

Here's what I was hoping to do:

VLAN for servers
VLAN for PCs at Office 1
VLAN for PCs at Office 2
VLAN for VOIP stuff

I was hoping to use the 3560 to statically route between the VLANs at
the offices by sending the traffic to the specific switchport.
So as an example the 3560 in Office 2 would have the server VLAN setup
and then have a route to the P-T-P switchport, etc..
Apparently this may not be possible.

What additional hw/reorganization would I need to make it possible?

Thanks.

OK, I think I understand what you're wanting to do now. If your
switches support a dynamic routing protocol (even RIP should probably
work OK in this case), it might make it a bit easier to configure
because you wouldn't have to worry about tons of static routes.

The only places you have to worry about the VLAN's is on the 3560's.
You only have to set up the local VLAN's on the local switch. So, the
3560 @ office 1 just needs Office 1's VLAN's added to its VLAN
databaset. And the same for office 2.

You just have to configure the 3560's to route between those local
VLAN's, and to have the attached router as its default gateway. Then,
you have to set up static routes on the routers. So, office 1's
router would have static routes to all of the office 1 VLAN's with the
3560's IP as the next hop. And office 2's router would have static
routes to all of the office 2 VLAN's with the 3560 at office 2 as the
next hop. Then on your routers you should set up static routes to the
other office's VLAN's. You would add static routes on office 1's
router to all of the VLAN's at office 2 with the office 2 router as
the next hop and vice versa.

You should try to use a dynamic routing protocol if you can, it'll
make it easier to configure, and easier to change your network
structure later on. I think the 3560's should support RIP even if
they have SMI, and RIP should work OK in this case. If you are using
RIP, then you should just add each of the local VLAN's networks to RIP
on each of the 3560's. And just add the networks (ie, the serial link
and link to the 3560) that are directly connected to the routers to
RIP on the routers at each office. And make sure RIP is enabled for
all of the appropriate interfaces. If you have EMI on your 3560's,
then I think you are even be able to use EIGRP or OSPF or something
much more modern than RIP.

Hope that helps a little,

Oliver

.

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