From: Chuck Church (cchurch@optonline.net)
Date: Fri Nov 22 2002 - 16:19:01 GMT-3
Tim,
I've never seen or worked with a content switch, but I'll give it a
shot. Once a workstation resolves a name through DNS, any traffic to/from
that host is done via the name it originally resolved, until the TTL for
that host expires. I doubt your setup has the 'backup' site servers
assuming the IP addresses of the 'primary' servers. If the content switches
do maintain session information on each other, you still need a way to let
the workstations know of the change to the backup servers/addresses. I'm
guessing the only way to do this is through DNS, ie changing the TTL for the
record to a real low number, like 10-30 seconds. Keep in mind I'm just
guessing here :)
Chuck Church
CCIE #8776, MCNE, MCSE
----- Original Message -----
From: "Tim Devries" <TDevries@cyence.com>
To: <ccielab@groupstudy.com>
Sent: Friday, November 22, 2002 12:25 PM
Subject: OT: CSS 11500 Adaptive session redundancy
> I know this is somewhat OT for this list, but there are a lot of smart
> people and CCIE's on this list, so I thought I might pose a question:
>
> Is it possible to configure Adaptive session redundancy on css11500's
> located in different datacenters? (I.E. no layer 2 connection between
> content switches, a lan extension between datacenters located 1000+km's
away
> is not feasible)
>
> The reason I ask is I've configured my 11800's for global load balancing
> according to this link:
>
>
http://www.cisco.com/en/US/products/hw/contnetw/ps789/products_configuration
> _example09186a008009438a.shtml
>
> However, it seems Cisco is embellishing when it says, "Unplug (or suspend)
> all the servers on the French CSS. Click on a link on the page. The CSS
has
> redirected the browser seamlessly to a server on the remote CSS." In
fact,
> this is not what happens.
> When I unplug the servers at one location, and click a link in my app, I
get
> a page cannot be displayed error, and doing a netstat -n on my machine
shows
> that a SYN is being sent to the downed location. Opening a new browser
and
> inserting the link does direct me to the location that is up, so I can
> verify that the APP session between switches is exchanging the correct DNS
> info. This is far from 'seamless' though.
> According to that link, when I disconnect the servers at the 'hot' site, I
> should be seamlessly redirected to the servers behind the CSS at the
'warm'
> site.
>
> Doing a packet analysis on the transaction (from the point of downing the
> services to clicking the link), shows that my browser is attempting to
> connect to the dns address it received when it first connected to the site
> at the 'hot' datacenter. Seeing as how the servers are down at that
> location, I get a page cannot be displayed. When I open a new browser I
get
> the new dns entry, and of course am redirected to the new location.
> However, Cisco promised 'seamless failover' (i.e. within a browser
window),
> and it has not delivered on this, so I am wondering if there is another
way
> to accomplish this. From what I can tell about ASR it looks like the
> switches cannot be geographically seperated if they want to maintain
state,
> but perhaps someone else out there has encountered a similar issue with
> Cisco products and found a solution?
This archive was generated by hypermail 2.1.4 : Tue Dec 03 2002 - 07:23:09 GMT-3