Axel AX3000 65 User's Manual - Manual (Page 235)

Appendix
AX3000 - User's Manual
223
Example of name resolutions: looking at the host table in Chapter 3.1.3 the
name resolution attempts are:
- as400: this is not a full name, the resolution is first made with the first
DNS domain (as400.servers.axel.com). Then, in event of failure, with the
second DNS domain (as400.terminals.axel.com). Then, in event of
failure, the resolution is made with the name itself (as400).
- linux: an IP address is associated. No DNS resolution.
- www.axel.com: this is a full name. The resolution is first made with the
name itself (www.axel.com). Then, in event of failure, the resolution is
made with the first DNS domain (www.axel.com.servers.axel.com). Then,
in event of failure, with the second DNS domain
(www.axel.com.terminals.axel.com).
b) Resolution Method
To resolve a name, the AX3000 sends DNS requests to the DNS server(s).
If a DNS server sends back a positive response, then the IP address is found
and the resolution operation is completed. If not two cases of failure are
possible:
- Receiving a negative response: the name is not known by this DNS
server. The AX3000 will retry with a new DNS request or with the second
DNS server.
- No response (time-out): after a few seconds the DNS server has not
sent back a response. The AX3000 resends the same request to the
DNS server.
Note: after 4 time-out errors on the same DNS server, this server is
"removed" from the resolution operation.
Note: if a response previously considered as a time-out error is received, this
response is treated as a valid response (positive or negative).
The AX3000 requests a recursive search to the DNS servers (and not iterative
search). This means that the DNS server must search itself for a DNS server
which is able to resolve the required name.