From: Tim Devries (TDevries@cyence.com)
Date: Fri Nov 22 2002 - 14:25:23 GMT-3
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?
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