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New Member

Two LD430 connected in daisy chain with cat6500

I've try to connect two active LDs in daisy chain structure to establish three level architecture of my web service.

All is connected to cat6500/Sup2/PFC2 with vlan created as below:

.

(dots are for whitespacing ;-)).

.

Internet

.....|

MSFC2(L3-vlan int) - VLAN1- LD1 - VLAN2 - LD2 - VLAN3

..........................................|............................|..........................|

...............................front server.........apps server.....database server

.

.

-The only L3 interface is terminated on MSFC2 in VLAN1

-Front servers are connected to VLAN1 and are not balanced

-Application servers are connected to VLAN2 and are balanced by LocalDirector LD1

(VIPS for Apps servers are configured on LD1)

-Database serveres are connected to VLAN3 and are balanced by LD2

(VIPS for Apps servers are configured on LD2)

.

The idea is to comunicate in pairs:

-Internet - Front Servers (without balancing)

-Front Servers - VIPs/LD1 - Applications servers

-Front Servers - VIPs/LD2 - Database servers

-Application Servers - VIPs/LD2 - Database servers

There are also needs to make additional communications:

-Database servers - VIPs/LD2 - Applications servers

-Application Servers - VIPs/LD1 - Front servers (reverse proxy http connestions)

-Database servers - VIPs/LD1 - Front servers (reverse proxy http connections)

.

Is that topology and solution possible to establish using LD and cat6500 ?

.

I've tried to do it so network goes down when connecting LD2 because of STP troubles reported on cat6500, seems to catalyst dont want to support two active (and absolutely separate and different in config and connections) LocalDirectores because of interVlan leeking or something like that ;-((

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How to do it only with LD/cat6500 (without CSM and/or CSS) ?

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Regards

Maciej Kolodziej

5 REPLIES
Bronze

Re: Two LD430 connected in daisy chain with cat6500

I think this is workable, but maybe not in the 3-level model. Problem being, that balanced TCP connections need to pass "through" the director, i.e. in one interface and out another. This could cause issues if devices on VLAN3 need to communicate to VIP's on LD1.

Another issue is that sessions from VLAN1 and beyond to/from VLAN3 need to traverse two LD bridge hops, which could have performance implications, and causes LD1 to process a lot of traffic that it might not really need to.

I think a better design would be to have both LD1 and LD2 connect directly to VLAN1 in more of a star topology. That way, you shouldn't run into any illegal "one-armed" LD traffic patterns, and you would not have more than one LD bridge hop for traffic between the outside world and VLAN2 and VLAN3.

New Member

Re: Two LD430 connected in daisy chain with cat6500

Thanks for answer,

I've thinking also about "star topology", so this is not a solution for me because of other, not shown in description, reasons.

Especcialy main problem is that most of trafic goes in pairs of servers:

- Internet to/from front

- front to/from applications

- applications to/from database

(rest of the communications beetwen servers cost about 15% of traffic)

and one LD couldn't service such volume of traffic on it (this is not interface wire speed bridge ;-(( )

.

...Internet

........F

LD1..LD2

App....DB

.

in case of star topology one of LD will be overloaded by network traffic (not by balancing operations) beetwen server groups (I know about it because I've already something like that in my net) ....

.

Regards

Bronze

Re: Two LD430 connected in daisy chain with cat6500

Ok, in that case the 3 level design will work just as long as devices in VLAN3 don't need to communicate to a VIP on LD1.

I suppose if need be, a second VIP for the app servers could be created on LD2 for communications from VLAN3.

The physical dependencies of having all traffic pass through the bridge in the case of the LD, was one of the driving factors that resulted in my companys switch to the CSS architecture.

New Member

Re: Two LD430 connected in daisy chain with cat6500

speaking about CSS, I can't use them because of dispatch mode redirection which is used here ;-))

Bronze

Re: Two LD430 connected in daisy chain with cat6500

I know the CSS allows you to configure redirect services, but I've never used dispatch mode, so I don't know how they do or don't compare.

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