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Re: ntpd listening on alias interfaces seems non-trivial



Ntp uses its own protocol on top of UDP. Each ntp packet includes source
and destination addresses of the communication. The ntpd server uses this
data and checks if a answer came from the same host the request was sent
to. If this is not the case, it assumes something is wrong.

In your setup clients connect to one ip(of the alias) and you send the
reply via your main interface. These ip's then don't match. I don't think
it is possible to use alias interfaces with ntpd. If you do get it running
somehow please let me know.

> I have been attempting, without success, to get ntpd listening on an alias
> interface on one of my general purpose boxes. It seems that ntpd prefers to
> listen on localhost:ntp and eth0addr:ntp. It opens a socket for *:ntp as
> well, but does not respond to queries on other addresses. Here is some LSOF
> output demonstrating this..:
>
> # lsof -p 16667 |grep UDP
> ntpd    16667 root    4u  IPv4    4493134             UDP *:ntp
> ntpd    16667 root    5u  IPv4    4493135             UDP localhost:ntp
> ntpd    16667 root    6u  IPv4    4493136             UDP hostname:ntp
>
> I checked the archives, and it seems another poster had similar trouble in
> Dec'02, but there were no apparent follow-up posts. Google has also been
> less than revealing on this topic. All suggestions entertained.
>
> --
> Jeff
>
>
> --
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Marius




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