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SSH Tunnel
Secondary Server
Figure 99. Dynamic DNS Update - Secondary Server
A secondary DNS server can be used e.g. if no connection to the
primary DNS server can be accomplished. An alternative DNS ser-
vice with identical or different host name can be used for the sec-
ondary DNS server.
Note: In principle, a secondary DNS server is not necessary for a
dynamic DNS update.
The SSH tunneling enables other hosts on the internet to connect
to the A850 by using a SSH server as a proxy, even if the A850 has
no official IP address or cannot be directly reached from the inter-
net, as long as the following preconditions are met:
•
The A850 must be able to initiate SSH connections to a SSH
server which can be reached from the internet. If there is a
firewall between the A850 and the internet, connections to
the SSHserver's IP address and port must be allowed by the
firewall.
•
The SSH server must support SSH version 2 and allow remote
port forwarding without a parallel shell connection.
•
The user must create an account on the SSH server.
The A850 supports two SSH tunnel connections: a primary which is
tried first and a secondary which is only used if the primary con-
nection can't be established. Both SSH servers must support
remote port forwarding (for more than one port if necessary).
Note: You can also perform the Console Commands of the A850
from a remote PC through a SSH tunnel if you define a
"Remote Telnet port" at the SSH server.
105
CHAPTER 3
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