Telnet over PPP connection

Tags:
Ethernet
Networking
TCP
We have two AS/400s. System A & B(they are connected with TCP/IP). We have a dial-up PPP connection setup from system B to a remote site. We can connect from system B to the remote site with no problems and use TELNET and FTP. But when we try to TELNET from system A, through system B, to the remote site, we get an active connection but never get a sign on screen...it times out. Is this a routing issue that the remote system can't find the way back through system B to system A?

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When ‘B’ initiates a connection to the remote site. It dials an external modem on a serial port, or an internal modem (which thinks it is a serial port). The end of that process to enable telnet is the acknowledgement of an interrupt (hardware even if wirtualized). Every time I have seen this sort of problem (and it is still prevalent) the secondary machine “A” requests a tcp/ip connection to the remote site from “B”, and ‘B’ looks at the routing table gives ‘A’ the last valid IP address and stops, never having dialed the remote site. Or having dialed the remoste site never passes the new IP address back to ‘A’.
It is a place to start – Good Luck.

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  • Cptrelentless
    Could be. Did you try adding a static route?
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  • Davidm14386
    Don't know much about routing/networking, so I'm not sure what route to add and what machine to add it on. Here are the IP addresses of all machines involved. System A: 10.0.0.3 System B: 10.0.0.11 Remote System: 10.100.200.2
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  • Amigus
    Without knowing the netmask and other details about the network layout it's difficult to assertain what route(s) you need to add and where. In essense all systems in the path need to reach all other systems by way of a network route or the default route. From the information you provided: System A: 10.0.0.3 System B: 10.0.0.11 Remote System: 10.100.200.2 I'd guess that System A needs a route through system B to remote system. Assuming that all networks have a netmask of 255.255.255.0 you'd need to add a route to system A as follows: net 10.100.200.0/24 via 10.0.0.11 In addition the remote system needs to know that 10.0.0.0/24 is available through System A. Sorry that this is so vague, confusing and possibly wrong. If you provide a more precise layout of the network I could probably give you better advice.
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  • Steview
    You have probably already checked this but I would also review the system values on both AS400s to ensure that your signon from A can be passed to and is valid on B. It would worry me that you do not get a sign on screen. Audit requirements often insist on specific system values that will stop this - sorry I do not know the values off hand and currently have no access to an AS400
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  • RiddleFixer
    Wow, people still do use telent, eh? :-) When routes are in question, try ping and traceroute. If ping gets you the right replys from both sides, it is likely there is not a problem with the routes or connection and you can focus your attention on other areas such as tcpwrappers or firewalls or other security policy type stuff. If the ppp connection disrupts your routes, you will likely see some other problems as well. route -n should shed some light. good luck
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