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X25 configuration guidance required please

I'm looking for some assistance on X25 configuration.

We have had an X25 serial line to our provider installed at our company premises.

I have to configure our 7206 router accordingly.

The X25 interface is connected on Serial3/1 of the router (on Serials 3/2-6 we have IP connections elsewhere)

Now, what do I have to do to configure this interface for X25 communications?

The information I've been given from the provider is:

Customer is DTE

Level 3 settings: Window Size 2

Packet Size 8

LCN Range 1024-1030

And a few different 14 digit NUA's - I'm assuming these are the X121 addresses that I need to communicate with at their end?

So what do I configure at my end?

So far I have:

interface Serial 3/1

encapsulation x25 dte (think dte is the default anyway)

x25 ltc 1024

x25 htc 1053 (are these lines correct for the LCN Range the provider has specified?)

I'm not sure what else is required and how to use the information from the provider appropriately? Should I have been given an X121 address for my interface? How do I route to their network, etc?

As you can seem I'm a complete X25 novice so any help and guidance that you can give would be appreciated!

Thanks.

5 REPLIES
Bronze

Re: X25 configuration guidance required please

Hi,

you definitely need an X.121 address to map your IP address to. You need to specify your local X.25 address, and use an ´x25 map´ statement to map your address to the provider. The whole configuration needs to look like this (IP addressing is arbitrary, change that to your real IP address):

interface Serial 3/1

ip address 172.16.1.1 255.255.255.252

encapsulation x25 dte

x25 address 1234

x25 map ip 172.16.1.2 5678

x25 ltc 1024

x25 htc 1030

x25 subscribe windowsize permit 2 2

x25 subscribe packetsize permit 16 16

172.16.1.2 is the remote IP address, and 5678 the remote X.121 address.

You also need to globally enable X.25 switching with the global command ´X.25 routing´.

That should pretty much do it. Give me a shout if it doesn´t work.

Nethelper

New Member

Re: X25 configuration guidance required please

Thanks a lot, that's very helpful. I still have a few questions though:

Should it be my service provider that allocates the X121 address to me then? Or do they expect me to have my own X121 address (if so, how do I obtain one. I'm in the UK)

Also, for the remote IP address - why does it need an IP address if it's purely an X25 connection? I have a number of NUAs (X121 addresses) that I need to communicate with. Does that mean that I need to have an IP address mapped to each one?

Isn't there some way that I can just say, for this NUA - use interface Serial3/1? i.e. without having to map it to an IP address?

Apologies if I've misunderstood any of the above! I've never worked with X25 before so it's all a bit strange to me!

Bronze

Re: X25 configuration guidance required please

Hi,

my mistake, the above is for XOT, or X.25 over TCP/IP. For a pure X.25 the configuration would be:

x25 routing

!

interface Serial0

ip address 172.16.1.1 255.255.255.252

no ip mroute-cache

encapsulation x25 dte

bandwidth XX (whatever your assigned bandwidth is)

x25 ltc 1024

x25 htc 1030

x25 pvc 1 interface Serial0 pvc 5

x25 subscribe windowsize permit 2 2

x25 subscribe packetsize permit 16 16

I am not sure about the number of the PVCs, who is your provider anyway ? I might be able to check with them.

Consult the document below as well:

X.25 Protocols

Configuring X.25 PVCs

http://www.cisco.com/en/US/tech/tk713/tk730/technologies_configuration_example09186a0080094719.shtml

Nethelper

New Member

Re: X25 configuration guidance required please

Hi,

thanks for the response, thats very helpful indeed! (Apologies for not replying sooner, I hadn't noticed your additional reply until now!)

I'm in the UK and my provider is essentially BT - though we go through a 3rd party so that complicates things further!

I'm still waiting to hear back from then on how to test this out so if any further questions arise (which I'm sure there will be!) I will let you know!

Thanks again.

New Member

Re: X25 configuration guidance required please

Hmmm, not too sure I fully understand the PVCs. However, I'll have a look through the link you provided and see if I can make more sense of it.

What I still don't get though - how do I route to the NUA's (X121 addresses) they have provided for the remote end?

I have 3 remote NUA's that we want to communicate with, so presumably, as with IP, I have to set up some kind of static routes to say, for these NUAs, use this interface? Is that correct? If so, what do i need to configure here?

(I think the thing that is most confusing for me is translating between the information Cisco provide and the information our X25 provider supplies!)

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