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Internet Related/Filtering/Firewall Thread, Can I divide T1 internet connection into two offices with different subnet? in Technical; Hello Guys, First of I would like to THANKS to even try to help me with this, so let me ...
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    Can I divide T1 internet connection into two offices with different subnet?

    Hello Guys,

    First of I would like to THANKS to even try to help me with this, so let me start my scenarios.


    Building A (both building right next to each other)
    1. I have a T1 internet connection with 30 static available IP range.
    2. T1 is connected to my ASA5510 into eth0/0 (which is Outbound), on ASA5510 eth0/1 is my Inbound (where the LAN & VLANs are which consist of three Cisco 3560 switches) , ASA5510 eth0/2 is my DMZ (Exchange & DC also using 2 static IPs).
    3. Cisco 3560 sw1 is physically connected to sw4 on Building B. (all have cisco 3560 & are on it's on vlan for management)

    Building B (on different subnet)
    1. Have DSL internet connected to a netgear router witch is connected to cisco 3560 sw4.


    questions
    I would like to get rid of Building B DSL internet and share the T1 from Building A. Is it possible for me to do this?

    What I know is just run the internet wire from Building A sw1 to sw4 on Building B and it should give T1 internet access. HOWEVER that will be the same subnet as Building A which I don't want. I want Building B to be on its own subnet but share the T1 internet connection from Building A.

    If i'm missing any information please let me know, but I do GREATLY appreciate any help.

    Joe

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    A T1 is basically a straight through CAT5, when thinking about it in simple terms. I don't know if you've ever experimented with sending 2 subnets over a CAT5, but it works. You really can send as many subnets over a cat5 as you have of ports on a switch on each side of the CAT5. You can have one PC on one subnet and it will talk to the PC on the same subnet on the otherside of the cable. Then on the two sides, put another PC on another subnet and put another PC on the otherside of the cable on that same subnet and the second two sets of PCs could talk. But subnet1 PCs and subnet2 PCs would have no way of communicating with eachother without a router that could route between the two subnets.

    So, if you have it setup with your two buildings so they're on seperate subnets, I don't see why you couldn't have a switch on the headend and a switch on the far end. Then you'd have to have a router on the head-end that would route between the original T1 subnet and the DSL subnet but both subnets would be riding over the same T1 line now.

    I guess I never did anything like this with a router. I have setup two subnets on one CAT 5. More I'm thinking about it, the routes are going to get weird with both routes being on the same port. But most routers, you can specify the source network, destination network and then the next hop far end IP. So, I'd try setting it up. You would have legit next hop IPs. They'd both be on the far end of the same T1, but the router doesn't need to know or care.

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    Thank You dorlow for the response.

    But how do I come to share this T1 internet connection from 1st to 2nd office? I think I would need an internet ethernet line from Building A with an external IP Address to be connected to the Netgear router in Building B, question is how do I come to do this? or where do I start?

    Thanks for your help & time.

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    How far apart are the buildings? Are they next to eachother or a block or two apart? If they're relatively close, you just need to string a wire from one building to another building. The company I work for does stuff like that all the time. There's certain right ways to do it. I'm not the wiring guy. But it will be a point-to-point similar to the T1... but unlike the T1 where the CO owns it, this new wire you'll string, you'll own the wire. So, there will be no public IP at all. It will all be internal IPs going over that wire. It will be logically just coming off one switch port in the building that has the T1 and going into the other building into another switch.

    Your best bet would be to VLAN the first switch and use sub-interface on your router so you can route beween VLAN1 and the VLAN you're going to put the one port that's going to go to the other building. Then setup your router to route between the two VLANs.

    Do some research on Cisco routers and sub interfaces and VLANs. You can VLAN a switch so the switch thinks it's multiple smaller switches. Then you can assign a sub interface of the router to those VLANed switched ports. Then you can setup a routing protocol, such as IGRP or OSPF to route between those sub-interfaces and do exactly what you want to do.

    Here's some information for you...

    Subinterface - Wikipedia, the free encyclopedia

    Really, what you should do is post this question to a Cisco Networking forum. I took my Cisco classes about 7 years ago and I haven't really touched Cisco since. I'm Windows server guy now, so this isn't my specialty. I know it's possible because I've done it, but it's been a while since I've looked into exactly how to make it work.

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