resolv.conf defaults

Glenn L. Stewart — Mon, 11 Feb 2002 03:00:30 GMT

I would like to change certain entries in a vanilla resolv.conf to include retry and retrans as recommended by the forum previously.

I have read two man pages from other non HP-UX man pages due to the fact that the HP-UX man page is not a decriptive about these settings as I would have liked.

I found these:

retry:n Sets the number of attempts made to connect to each name server. While retry:0 is allowed, it is equivalent to retry:1. The default is 4.

retrans:n Sets the basic retransmit timeout, in seconds. The default is 5. An exponential backoff algorithm is used, so the default values for retry and retrans result in 5+10+20+40=75 seconds of total timeout for each name server. While retrans:0 is allowed, it is equivalent to retrans:1.

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Using a non working DNS entry (i.e. incorrect ip for entry nameserver). I produced this result for ping (uses gethostbyname).

Vanilla resolv.conf

Result:
# timex ping prddb0
ping: unknown host prddb0

real 2:30.06
user 0.04
sys 0.03

With an additional.. in resolv.conf
retry 2
retrans 1

Result:
# timex ping prddb0
ping: unknown host prddb0

real 0.10
user 0.05
sys 0.02

I have had itrc members recommend retrans 3000 - this conflicts with the man page above. But with the evidence above, the "defaults" must be incorrect as per man entries above:

Using "man" defaults from above (i.e. should be no change on vanilla resolv.conf)

retry 4
retrans 5

Result:
# timex ping prddb0
ping: unknown host prddb0

real 0.23
user 0.04
sys 0.03

Obviously the defaults for other Unix flavours (retry=4,retrans=5) are not equivilant to the defaults used by HP-UX.

I doubt retrans default is 5 on HP-UX

Another example using only:
retry 4

Result:
# timex ping prddb0
ping: unknown host prddb0

real 2:30.07
user 0.05
sys 0.03

From this, I can assume that default retry is as above, but retrans is certainly not default 4

My questions are:

Q1: What are the default retry and retrans used for HP-UX.
Q2: What would you suggest the optimum defaults to be, given that 2 minutes, 30 seconds (above) is unacceptable before resolving from a secondary DNS server (the primary being non pingable in the above example - with no secondary hence timex showing delay).

Thanks

Glenn

Re: resolv.conf defaults

Bill Hassell — Mon, 11 Feb 2002 03:42:07 GMT

Using man pages from other flavors of Unix can create problems. HP-UX options (per the HP-UX man page for resolv.conf) lists ndots: as the only option for resolv.conf.

However, if you have the minimum patch PHCO_20098 (10.20) or PHCO_22076 (11.0) (or successor patches) then retrans: and retry: are available. Alternatively, the environment variables RES_RETRANS and RES_RETRY can be set for the same results.

Unfortunately, all versions of 10.20, 11.0 and 11i do not have updated man pages yet.

However, I would seriously consider using nsswitch.conf rather than shorter resolv.conf timeouts. IP/hostname lookups occur much more often than you would expect (ie, once for every filename on a network backup system). By configuring files, then DNS, name resolution for important addresses is virtually instantaneous, requires no LAN traffic, and survives unreliable DNS servers.

topic Re: resolv.conf defaults in Operating System - HP-UX

resolv.conf defaults

Re: resolv.conf defaults