[Sussex] Test of smtp and query about DNS resolution

[Jon Fautley]

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Tony Austin wrote:
|>Mozilla seems to be taking a while to resolve hostnames, am I right in
|>thinking that if I put two DNS servers into /etc/resolv.conf this will
|>speed things up even though I'm using DHCP?
|
| That's not the way I understand it.  You can put extra DNS servers in
| /etc/resolv.conf in case the first one doesn't respond in a timely manner,
| so two could make it seem faster but probably only if the first one was
| very slow.

Yup. Also, make sure that there's no 'search domain.name' line in the
resolv.conf as this can make things really slow. DNS works in the
following way if you have a 'search' line:

* you request www.sussex.lug.org.uk
* resolver looks at resolv.conf and finds an ending suffix and the
nameserver (suffix = 3ait.co.uk in this case)
* resolver requests www.sussex.lug.org.uk.3ait.co.uk - fails
* the resolver then does the normal DNS thing of asking for the uk
servers, then who's authorative for .org.uk, then whos the nameservers
for .lug.org.uk, then what/who is sussex.lug.org.uk, then finally,
www.sussex.lug.org.uk.

It's not suprising that DNS is slow ;)

| I found that using my broadband router as a DNS caching server was
| unreliable and hterefore I let my ISP's servers do the hard work.
| However, in theory a local DNS cache should work faster.

Caching servers in most routers i've used have turned out to be shite.
They don't tend to handle round robin DNS, which is a pain, and breaks a
~ lot of sites. Local DNS caches to tend to speed things up a little - I
run a DNS server at home, and it makes stuff nice and fast :)

| DHCP doesn't have anything to do with it - it just dishes out the IP
| addresses.

Err, DHCP assigns many things, including IP address, Netmask, Default
Gateway, DNS servers, WINS servers, bootp server (and associated info),
and hostname, and prolly many other things. DHCP will, and does,
overwrite resolv.conf.

Jon
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