Sorry Tom, didn't quite get this: "In this scenario you can get the advantages of caching with the Firewall client, and you can take advantage of NLB when using the firewall client. So, all you lose are some nominal gains conferred from CARP" Which scenario/option? - do you mean option 3? If so, which network do you need to enable it on? Intra-Array "feels" right, but not 100% sure... Jason Jones | Security | Silversands Limited | Desk: +44 (0)1202 360489 | Mobile: +44 (0)7971 500312 | Email/MSN: jason.jones@xxxxxxxxxxxxxxxxx<mailto:jason.jones@xxxxxxxxxxxxxxxxx> From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Thomas W Shinder Sent: 14 July 2008 13:25 To: isapros@xxxxxxxxxxxxx Subject: [isapros] Re: Web Proxy with NLB - Back to basics! Hi Jason, I think you've got the analysis down right. CARP and NLB have never been two great tastes that taste great together. In this scenario you can get the advantages of caching with the Firewall client, and you can take advantage of NLB when using the firewall client. So, all you lose are some nominal gains conferred from CARP. Tom Thomas W Shinder, M.D. Site: www.isaserver.org<http://www.isaserver.org/> Blog: http://blogs.isaserver.org/shinder/ Book: http://tinyurl.com/3xqb7 MVP -- Microsoft Firewalls (ISA) From: isapros-bounce@xxxxxxxxxxxxx [mailto:isapros-bounce@xxxxxxxxxxxxx] On Behalf Of Jason Jones Sent: Monday, July 14, 2008 4:05 AM To: isapros@xxxxxxxxxxxxx Subject: [isapros] Web Proxy with NLB - Back to basics! Hi All, After a bit of debate and some guidance really...I may be a little clumsy trying to get my thoughts across here, but please bear with me :) After reading the recent blog post from Yuri/Jim called Understanding By-Design Behavior of ISA Server 2006: Using Kerberos Authentication for Web Proxy Requests on ISA Server 2006 with NLB this got me thinking about an old conundrum that keeps coming up now again in terms of web proxy fault tolerance. As stated in the above post (and the current best practice I think) it is recommended to configure web proxy clients to use client-side CARP by way of the array script. However, client-side CARP is not "NLB aware" and hence the script contains references which related to the server DIPs and not the NLB VIPs. Consequently, NLB is merely used to provide fault tolerance and load balancing for access to the script only. I am aware that the array script includes a basic form of fault tolerance, but this is not really a "proper" fault tolerance solution and in my experience is not sufficient for most customers looking for web proxy availability. So, based upon this, I understand we have the following options: (1) Accept the limitations in terms of client-side CARP fault tolerance and choose performance as the overriding factor (2) Force web proxy clients to use a manual proxy server definition and direct requests to the NLB VIP and lose the benefits of client-side CARP in favour of NLB fault tolerance. Neither of the above options is ideal in my experience - what do you guys normally choose/do??? I have also heard talk of a third option where we can use server-side CARP in conjunction with option 2 above. The downside is that each array member will now how to process the script on behalf of the client, which adds CPU cycles per array member. This seems to be a very good compromise to me, but I have never been that clear on how best to configure this - which network should CARP be enabled on - Localhost, Internal, or the custom Intra-Array network???? Also, what sort of CPU impact are we looking at here? Is it just a few more % per array member, or are we talking about needing an extra CPU per array member to cope with demand? In my experience, if customers are looking at EE with a view to using NLB fault tolerance (as many do) then they are a little disappointed with option 1, as in reality NLB is not really providing the benefits they anticipated. However, the loss of the CARP is also a bit of a blow if option 2 is chosen. So, option 3 seems to be the only viable "best of both" workarounds? Apologies if this is a little back to basics, but I am keen to make sure I get my thinking straight on this one as it keeps coming up and I want to make sure I gets my ducks in line from now onwards :) Any other ideas/thoughts welcome! Cheers JJ ________________________________ This email and any files transmitted with it are confidential and intended solely for the use of the individual to whom it is addressed. If you have received this email in error, or if you believe this email is unsolicited and wish to be removed from any future mailings, please contact our Support Desk immediately on 01202 360360 or email helpdesk@xxxxxxxxxxxxxxxxx If this email contains a quotation then unless otherwise stated it is valid for 7 days and offered subject to Silversands Professional Services Terms and Conditions, a copy of which is available on request. 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