| The Care and Feeding of ISDN4BSD | ||
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| 10.2 sppp and isp0 | 10 Setting up a | 10.4 Troubleshooting the PPP |
10.3 telnet to the Remote System
After starting isdnd and running the script described above, everything should be fine and we are able to test the link. I'll use telnet to show what will happen:
- <hm@hmpc>/home/hm telnet 192.76.124.10
Trying 192.76.124.10...
telnet: Unable to connect to remote host: Can't assign requested address
<hm@hmpc>/home/hm telnet 192.76.124.10
Trying 192.76.124.10...
Connected to 192.76.124.10.
Escape character is ']'.
I have to run the telnet command two times. The first one instructs isdnd to dial out. When a B-channel connection is made, the PPP protocol starts to run and negotiates the options with the remote side of the link: the important thing which happens here is that our own interface address is set to an address which is specified by the remote side. This can be seen by issuing the command ifconfig isp0 before dialing out:
- <hm@hmpc>/home/hm ifconfig isp0
isp0: flags=2911<UP,POINTOPOINT,PROMISC,SIMPLEX,LINK1> mtu 1500
inet 0.0.0.0 -> 192.76.124.10 netmask 0xffffffff
and then again at the time the connection is active:
- <hm@hmpc>/home/hm ifconfig isp0
isp0: flags=2951<UP,POINTOPOINT,RUNNING,PROMISC,SIMPLEX,LINK1> mtu 1500
inet 192.168.168.168 -> 192.76.124.10 netmask 0xffffffff
As you see, the interface flags show an additional item RUNNING meaning that this interface is currently active and you also notice that our own IP address has changed from 0.0.0.0 to 192.168.168.168, which is the address our interface was assigned to by the remote system.
This address assignment taking place is also the reason for the first telnet connection failing with the error message ``Can't assign requested address'': this telnet connection uses the address 0.0.0.0 as its destination address, because the address negotiation and assignment has not yet taken place and 0.0.0.0 is an illegal address in such packets. After the address assignment has taken place, the second telnet succeeds connecting to the remote system.
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