You have the basic idea. the Local Director
load-balances per packet. Now you are talking about 2
servers behind the LD and you want the same user
(session) to continue to go to the same server till
the transaction is complete (usually do to the fact
that the server keeps the session ID and tracks it,
very common.) What you will need to use is the STICKY
command. This command will allow you to send a
certain client session to the same "real" server.
So once you create your 1 virtual server and 2 real
servers type in the sticky command and apply it to the
Virtual address. There are foure ways that the box
will do the sticky:
IP: Based on source and destination of the request.
The problem here would be in the case your users are
coming from a PAT. Lets say you have one large user
base coming in with the same source. The LD would
send these requests from that IP to one real (thinking
it's the same session.) This could get in the way of
actual load balancing. But th egood thing is that it
works and is very easy to configure and make sure it
works.
SSL: This is the other sticky type which has been
supported since aleast ver. 4.4. This tracks the SSL
session ID and makes sure the client with the same SSL
Session ID keeps going back to the same server. This
had some problems with a couple of IE4.? vers, where
the browser would request a new SSL ID too soon (the
SSL TTL on the browser was set to small.)
App Cookie: This was introduced in the 5.? releases.
This allows you to define a session based on the
cookie yor app gives to the session. This is assuming
that you use Cookies. If your using cookies this is a
pretty solid solution, though it is a bit slower than
the previous two.
LD Cookie: Released along witht the previous. You
also have the option of having the LD assign cookies
to the traffic (a great option when your app doesn't)
Again this is a bit slower than the first two.
On the cluster issue, remember that the cluster has a
single VIP and this is the way it should be accessed.
It will do it's own load-balancing (hopefully.) So the
LD would be useless in this case, unless you have two
sets of clusters that you'd like to load-balance.
When installing also look at the way the LD is doing
it's load-balancing. By default it is set to
least-conn. That means the unit with the least amount
of open connections gets the request. This may or may
not be the right one for you, so read into them and
apply it to your scenerio.
Remember that your install is a very basic one:
You need to set the management IP
Set the Virt
Set the Real
Bind them
Set your sticky
The Default Gateway
and plug two interfaces to separate VLANS.
(I think thats it!)
Also remember that the LD is a bridge (and never
bridge it) the servers behind it use the same address
space as the network in-front of it and use the
default gateway of the network in-front of the LD.
I hope that helps, I'm sure I would spew out some more
if my fingers weren't tired!
Moe Tavakoli
--- Keith Whitfield <[EMAIL PROTECTED]> wrote:
> Thanks for the response. So, In what kind of server
> setup does
> LD work? Is there a way to disable load-balancing on
> the LD and
> configure it to work as a Redirector?
>
> I don't know if I am asking for something that LD
> doesn't do.
> But, I am confused at the scenario when LD is
> implemented and
> what are the things I need to keep in mind at the
> server sides
> when I go ahead with LD solution.
>
> Thanks
>
> <[EMAIL PROTECTED]> wrote...
>
> I’m not even sure it is possible to load balance
> between two
> servers in a cluster. Since clusters are generally
> presented as
> one server.
>
> Clayton
> “Keith Whitfield” <[EMAIL PROTECTED]> wrote
> in message
>
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> Hi...
>
> I am in the process of implementing a Local Director
> for the
> servers in our company. Right now in the process of
> documenting
> the requirements and design of it. I have some
> questions for
> which the cisco site don’t have information in the
> LD
> documentation. I have 2 servers on which I need to
> do load
> balancing as well as have a fail over redundancy in
> case one of
> them goes down. I can achieve this by the LD. But
> the traffic
> that goes via the LD are real time transactions and
> I don’t know
> how the application(our) will respond to these
> requests, since
> LD laod balances on a packet-packet basis. Basically
> we will be
> having 2 instances of the application running.So, my
> questions
> are
>
> 1.To achieve synchronization between the servers for
> every
> transaction that occur Do I need to have a
> clustering software
> for these servers?
>
> 2.Can I configure the LD to forward all requests to
> only one
> server (even though it is connected to another
> server) and make
> the second available when the first goes down?
>
> 3. Does the The sample configs in the LD
> documentation assume
> that the servers are already clustered or have only
> static data
> for the outside users?
>
> Any comments on this or if someone has a similar
> setup what I am
> trying to acheive , please reply back.
>
> Thanks in advance.
>
> Regards
> Keith.
>
>
>
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