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New Member

Cisco SX20 with an ISDN Link


I have 2 Cisco SX20 with ISDN Link systems that I want to connect over a LAN.

I have paired both units and given them ip addresses in the same subnet, my first question is what the defaut gateways of each unit should be pointing to...

My second question is what would be the best configuration option if I just want to have one unit call the other over a LAN.

Thanks in advance

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VIP Green

The IP default gateway should

The IP default gateway should be the IP Gateway of your Subnet (usually the IP address of your router).

To call one unit from the other, make the call as H.323 rather than H.320/ISDN and put the IP address in as the number to dial (assuming you're running the IL1.1 software on the ISDN Link and not the original IL1.0).

New Member

Hi Wayne,Thanks for your

Hi Wayne,

Thanks for your reply, I am running IL1.1 and 6.3 on the sx20.

My sx20 and ISDN Link are directly connected, do you mean that both the ISDN Link and the sx20 default gateway settings should point to my IP default gateway.

If I had to call one unit from the other over a layer 2 LAN could i just point one ISDN Link to the other and use their IP Addresses as each others default gateway.


VIP Green

The default gateway should be

The default gateway should be the the correct address for the subnet that each of the devices is connected to.

Your SX20 will have an IP address (say and your ISDNLink will have, as an example - both on the same subnet (subnet mask the default gateway will be the IP gateway on that subnet (usually

Your second SX20/ISDNLink, if on the same subnet may be for example, and  They still all use the same gateway ( if they're in the same subnet.

If the second device is on a separate subnet, then the IP gateway will be the gateway for that network (ie, if the subnet is, the gateway will likely be

If you're unsure, contact your local Network expert and they should be able to assist.

Once both devices are on the network, and have everything configured correctly, you should be able to do a direct H.323 dial from one to the other by dialling its IP address (dial the second device on from the first device

The ISDNLinks are only involved in a H.320 (ISDN) call.

New Member

Thanks again for your help

Thanks again for your help,

This is more or less how i had it set up, as it's just a small LAN there is no default gateway so i've tried it with no default gateway settings in either the sx20 or isdn link, ive tried just putting in a default gateway ip address from the same subnet ( the only subnet ) and i've tried making the sx20 ip addresses the others default gateway with no luck.

I now have both units on the bench connected to a 2960 switch along with a laptop, I can ping all devices and access the web gui's

The sx20 is connected to the isdn link and the isdn link LAN port is connected to the switch, all speed and duplex settings are 100Mbps Full ..... no auto configuration, h323 callsetting is set to direct but still nothing.

I think I might factory default all the units and start again as I'm sure it shouldn't be this hard.

Thanks again for your help wayne, this and other posts you have done have been very helpfull.

VIP Green

The IP Gateway should be the

The IP Gateway should be the same on all your devices on the same subnet, and is the device they all talk through to talk to a device on a different subnet/network/internet/etc.  So it should be the same on your SX20s and ISDNLink devices, your PC, Switches, etc - everything in the subnet.  Networking 101.

For your small test lab, it shouldn't matter if all your devices are in the same subnet, or if you want, just set the gateway to the IP address of your switch.

Perhaps to simplify things, as you're not using the ISDN at the moment - set up the SX20s without the ISDNLinks and get them working together, then introduce the ISDNLinks in to the equation.

Please remember to rate responses and to mark your question as answered if appropriate.

Edit: I've attached an edited copy of a config from one of my SX20s and it's ISDNLink, although it'll be a bit different to yours as it's registered to a Gatekeeper and managed through TMS, but a lot of the rest you should be able to copy/compare.

New Member

Hello,Just a quick question,


Just a quick question, if I factory default the sx20 via the GUI does that wipe all the interface software...?

ie.. the TC6.3.0.3

I have factory reset the 2 I have but nothing has come back up on the screen.

As you've probably guessed none of us are network engineers nor do we have access to any other than using the forums.

If I have removed all the software how do I get it back on.



VIP Green

A factory reset doesn't

A factory reset doesn't delete the TC software. 

Suggest you unplug it all and reconnect then turn it on again.

New Member

Thanks again Wayne,I got the

Thanks again Wayne,

I got the screen back using the remote key sequence " Disconnect, *#*#01#" which i found in some knowledge base document.

one of the units has come up with an error saying it's missing a Release Key so i can't access the Administrator Settings on that one anymore but I should get that fixed next week.