X.25 to TCP Translation on Cisco Router

[siddhartha.jain]

Hi,

I have the following setup:

POS <------> VSAT IDU <--------> Router <--------> IP Host

The POS is an Async Serial device with no networking protocol stack.

It pushes the character stream to the VSAT IDU (404622228888). The

VSAT IDU is connected over VSAT link to the router's serial port. The

router's serial port address is 404622221111. The router does X.25 to

IP translation and sends to to the IP Host.

The following is the config:

------------------------------------------------

version 12.0

x25 routing

!

interface Loopback0

no ip address

no ip directed-broadcast

!

interface Ethernet0/0

ip address ip-address-of-router-eth-int 255.255.255.224

no ip directed-broadcast

!

interface Serial0/0

no ip address

no ip directed-broadcast

encapsulation x25

no ip mroute-cache

no keepalive

x25 address 404622221111

x25 nvc 8

!

ip classless

ip route 0.0.0.0 0.0.0.0 ip-of-gateway

ip http server

!

translate x25 404622221111 tcp Server-IP port 8888 stream

----------------------------------------------------------------

This works fine. But shouldn't this be working like this:

translate x25 404622228888 tcp Server-IP port 8888 stream

since 404622228888 is the incoming X.121 address.

If I put "translate x25 404622228888 tcp Server-IP port 8888 stream"

in the config, it doesn't work.

Any ideas why??

Regards,

Siddhartha

[mikchung]

The x.121 address in the translate command is the in-coming or called address, which is normally the x.121 address of your interface with subaddress appended to the end. The subaddress portion is to distingush different servers/destinations.

I guess the calling or originating address is not used because the calling station could be talking to serveral hosts via the same link/interface and so we still need to know the destination address in order to route the messages correctly, therefore it is more straight forward to use the destination address in the translation command

[s.jankowski]

Siddhartha

What you wrote would be correct if the traffic is incoming from the VSAT to the router, whereas here the config is for translation to happen between the router and the IP host. Here the input is the serial interface of the router. Also no translation happens between VSAT and Serial Interface as both are using only X.25. So I think this is the correct config in this scenario.

[siddhartha.jain]

Hi,

Right now I have tested only with one VSAT and router. I am wondering what happens when I connect mutiple VSATs to the router. Will the router maintain a separate translation session for the stream coming from each VSAT?

Or in other words, if the router translates all traffic from serial X.121 interface of the router to the Ethernet IP interface, then will be club traffic from all VSATs and create one translation session (in which case I am screwed) or will it maintain a separate translation session for each VSAT-Router-IP Host connection?

Also, lets say I wanted to translate traffic coming from 2 VSATs and not translate traffic coming from other 3 VSATs connected to the same serial X.121 port. How would I do that then?

Too many questions, I guess. :-)

Regards,

Siddhartha