dsl to leased line connection

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Aug 6th, 2008
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Hi Friends

I need a quick help plz

One of my branch office has to be shifted from one building to another. before they ware connected through leased line on the serial interface of my router.

now in the new building they have dsl connection only.

Can we connect Leased Line to DSL Line?


is it possible that one side of the link is DSL and another side Lease Line on serial.

if possible how can we do the same?

your immediate response will be highly appreciated

thanks and regards


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dhananjoy chowdhury Wed, 08/06/2008 - 23:56
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If the two sites IP's are reachable from each other then you could opt for some kind of Tunneling , may be GRE / IPSEC etc.

It will be irrespective of whether its DSL or Leased line.

Jacob Samuel Thu, 08/07/2008 - 01:42
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as of now there is a leased line and both sites are connected each other.

my concers is connecting to different type of link-

dsl at bracnh side

serail leased line at HQ

will it communicate? If it works by creating tunnel? can you please describe how it is?



dhananjoy chowdhury Thu, 08/07/2008 - 01:59
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This is what I can understand from your setup .

Correct me if I am wrong.

Site HQ:

Router connected via Serial LL,

- Now there is IP connectivity with the ISP.

Branch side:

Router connected via DSL

- this will also have IP connectivity with the same or other ISP.

Now if this is the case do you have IP reachability between the sites ?

Jacob Samuel Thu, 08/07/2008 - 02:05
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yes, Branch side as of now not shifted to new building so connectivity now is thruogh LL only.

my concern is when they move to new building they have to connect to DSL at that time will i get ip reachability? since both are different technology.

if no what else i have to do to get the end-to-end connectivity?

if reachability is there tehn what else i have to take care for the proper data transfer?



dhananjoy chowdhury Thu, 08/07/2008 - 02:25
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One more thing you need to look at , is the new site going to have a DSL link for connecting only to your HQ or it would be a Internet Link.

If it is going to be a Internet link then probably you could look at some kind of VPN solution ,IPSEC - site to site, etc. for communication between your LAN subnets

Jacob Samuel Thu, 08/07/2008 - 02:31
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this will not be for internet. This just for connecting to the HQ office to access their application server.

Just the replacement of point-point serial link to dsl link.

So technology wise No Problem, even one is LL and other is DSL it will comunicate. right? what all i should configure on my cisco routers for the same.

branch - 2621

HQ - 7500



dhananjoy chowdhury Thu, 08/07/2008 - 02:43
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Yes, technology wise there is No Problem, even one is LL and other is DSL it will communicate and for reacability between the HQ 7500 and the Branch2621, the ISP will do it for you.

Now the question is to make communication between the LAN subnet in the Branch to the HQ servers,

- Is the ISP going to do the routing for the LAN IP subnet?

If yes, then no problem, only a basic routing configuration.

But If not, then you neet to set up a tunnel between the Branch2621 and the HQ 7500, and route the traffic via this tunnel.

Hope this helps.

Jacob Samuel Thu, 08/07/2008 - 03:03
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As of now its running EIGRP in the network.

i am attaching the cuurent config of the HQ router and branch router.

please review the config- as per this

what else i have to do? Need routing configuration only?

or do i need to create Tunnel interface or not?



HQ Router config

current config of branch router

dhananjoy chowdhury Thu, 08/07/2008 - 03:28
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See, its difficult to say the config now, because the new setup will be quite different from the existing.

In the existing setup, it is having a Point-2-Point connectivity between Riyadh and Al-Qasim, with subnet and also running EIGRP.

But in the new setup it may not be point to point. Just check with your ISP how they are going to provide the conectivity.

Jacob Samuel Thu, 08/07/2008 - 03:41
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Two other branches are already connected with DSL, but both side is DSL, you can find that in the HQ router Config. I can attach the config of the branch router which has dsl - dsl conection with HQ. Its like point-to-point link, there is not much changes in the config.

The difference now with the above cases is, it is DSL at both location and in present case it is LL at HQ side and DSL at Branch side.

If it is point-to-point like the above, then what else we have to do.

meanwhile i will try to verify with the ISP also.

wiating to hear from you



dhananjoy chowdhury Thu, 08/07/2008 - 04:35
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If its point2point like above, and you are using the same IP subnet, then there is no change on the HQ side.

On the Al-Qasim side,

- remove the config from the int S0/0

- you need to configure the DSL part.

nourelrayes Thu, 08/07/2008 - 21:35
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Both ends must have the same layer 2 protocol so using DSL in one side and PPP or HDLC on the other side won't work.

Both ends must have leased lines or dsl connection.

For some security reasons you should implement GRE over IPsec if you will use the DSL solution.

Jacob Samuel Sat, 08/09/2008 - 00:26
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Can anybody give me some more input on the same. there is multiple opinion in this.




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