Actually I wouldn't say most "wet themselves" but we also don't "assume"
anything. There are plenty of real instances of problems that many have
seen, and have even been posted here, that have been caused by having non-AD
DNS servers on a windows client. You also state "it never happens due to
the redundancy of DNS lookups" which is also false. Redundancy, in this
case, implies that if the DNS client doesn't find an answer on one server,
it'll ask another. There is a difference between getting an answer of
"record not found" and not getting an answer at all (a DNS server being
down, timeout exceeded, etc.) If a server replies that a record does not
exist, the DNS client will *not* query other servers. Also keep in mind
that the windows DNS client uses a fairly complex algorithm to decide
whether to talk to a preferred or alternate DNS server. This means that if
there is only one DNS server listed then the windows client will wait the
full time-out period. If, however, there are multiple servers listed, the
DNS client can, in some instances, decide that it would get a faster
response from an alternate DNS server based on previous response times from
the preferred DNS server.
In the real world, this means that if your internal DNS server is
temporarily under load and doesn't reply quickly enough (not completely
uncommon in an SBS environment where SBS is running DNS, AD, Exchange, and
Sharepoint) then the windows client will fire off a request to an alternate
DNS server. If the request is for an AD resource then the secondary server
will reply with a record not found and the client will believe the DNS
server is accurate (as it should, otherwise why list it as a DNS server) and
proceed as if the resource is unavailable. This is obviously inaccurate and
will cause client issues.
-Cliff
"Ab" <> wrote in message
news:#...
> Pabs wrote:
>> Hi, typically the SBS server would be handing out DHCP addresses.
>> However I'm wondering if the router should be the one handing out DHCP
>> addresses. For example, a colleague of mine had their SBS 2003 server
>> go down due to a hardware issue. Now no one in the office can access
>> the Internet. If the router was the DHCP server, I believe they'd
>> have Internet access right now from their workstations. Any thoughts
>> or experiences on this? Thanks.
>
>
> SBS should run DHCP as the norm. You can get redundancy if you enable DHCP
> on the router only when the server is down so clients will be able to get
> to the Internet - it would be a manual switch over and back when the
> server is back on.
>
> The alternate is to include your external DNS as a secondary DNS setting
> the the DHCP settings. Most wet themselves when this is mentioned and
> *assume* the Windows clients will have terrible issues as the 2nd DNS will
> be used on occasion and cause client errors etc etc - except it doesn't
> ever happen due to the redundancy of DNS lookups.
>
> Another alternate is to install DNS on a second server in the domain.
>
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