X. 25 Connect

Unanswered Question
Jan 22nd, 2010


our customer wants to use a 2821 gateway with an E1 controller in order to receive data via X.25.

Does anybody know how to configure this?

Thet gateway should answer the call and redirect it to an internal host.

Best regards Bjoern

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Giuseppe Larosa Fri, 01/22/2010 - 04:59

Hello Bjoern,

X25 can be transported over TCP in the so called XoT tunnels see


and dial commands to accept X.25 over an isdn


All examples I see are based on BRI and not PRI

for sure X.25 over D channel is supported only with BRI

X.25 traffic over the D channel can be used as a primary interface where low-volume, sporadic interactive traffic is the normal mode of operation. Supported traffic includes the Internet Protocol Exchange (IPX), AppleTalk, transparent bridging, Xerox Network Systems (XNS), DECnet, and IP.

This feature is not available on the ISDN PRI.

see config of peso router in this example it is using a PRI and it is used as an X25 switch


Hope to help


bjoern.kirchhof Fri, 01/22/2010 - 05:35

Hi Giuseppe,

many thanks for your detailled reply!

If I understood correctly, X.25 over ISDN can only be configure on BRI not on PRI correct ???

Regards Bjoern

Giuseppe Larosa Fri, 01/22/2010 - 05:44

Hello Bjoern,

that was my first impression.

However, ISDN over D channel is a special case and that is supported only on BRI

I just remember we moved XoT tunnels over an MPLS VPN with good results.

if you see config  of peso router in last example it is performing X.25 routing and it uses a PRI

X.25 is layer3 OSI so it configured with its own static routes and special mappings. This is what I can say

Hope to help


bjoern.kirchhof Fri, 01/22/2010 - 05:54

Hello Giuseppe,

many thanks once more for your fast assistance, I'll have a try on monday :-)

Regards Bjoern


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