CSM Deployment -Please Help

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I hope someone can provide some help, I need to deploy a CSM module for the purpose of Disaster Recovery, the objective is to be able have a standby server in site B so when the server(s) in site A fails to have the CSM direct all traffic to the standby server is site B (please see diagram) the problem is that I've been reading on CSM and I'm supposed to create "client vlans" and "server vlans" and I'm not sure if this applies to my topology (diagram) or objective, the 6509 that have the CSM's is connected directly with a layer 3 10 Gb link to the 6509 is site B that hosts the standby servers, where does the "client vlan" fit? users are already spread over different networks across the WAN/LAN, and what about the server vlan? I appreciate any input...



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Correct Answer by Jon Marshall about 8 years 9 months ago

Borman


"the "client Vlan" is where the VIP for the server farm will be placed (vserver) and will have an SVI on the MSFC, the "server Vlan" is the Vlan where the real servers are located, these real servers will use the CSM for routing out of their subnet, correct?"


if you are talking about routed mode on the CSM then you are spot on.


As for DNS, no the CSM cannot automatically register a DNS name although the CSM can automatically inject/remove a VIP IP address into the routing tables - this may be some use in a failover situation. If you are interested have a look at reverse route injection in the CSM documentation.


If you want automatic DNS updates for VIPs then you need to look at something like the GSS (Global Site Selector) which can communicate with the CSM's and point requests to different VIPs based on their availability.


One last point. More than happy to help when i can but there is a more suitable forum to post into


"Data Centre" -> "Application Networking"


one of Cisco's experts on load-balancing frequents that group as well as quite a few other very experienced people.


But like i say, more than happy to help when i can.


Jon

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Giuseppe Larosa Tue, 08/26/2008 - 10:57
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Hello Borman,

CSM provides hardware based load-balancing services: so you have real servers grouped in server farms. The CSM introduces virtual servers and users have to point at the virtual server IP.

The common way to deploy the CSM is in bridged mode: in this case it sits in the middle of two vlans that are called the client vlan and the server vlan.

Actually a single IP subnet spans over the two.

Here client vlan should mean the vlan between the MSFC and the CSM front end not the real clients.


In your case the standby server is behind another L3 device and this has to be investigated.

CSM can be used also in routing mode.


Hope to help

Giuseppe

Jon Marshall Tue, 08/26/2008 - 14:43
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Borman


Just to add to Guiseppe's post. The concept of client and server vlans exist for both routed and bridged mode on the CSM. The client vlan is basically the vlan that connects the MSFC to the CSM and the server vlan is the vlan where the real servers sit ie.


MSFC - vlan 10 - CSM - vlan 11


For both bridged and routed mode vlan 11 would contain the servers and vlan 10 is used by the 6500 switch to send packets to the CSM.


The difference is with bridged mode the same IP subnet is used for vlan 10 & vlan 11 and the MSFC has an SVI for that IP subnet. The CSM is seen merely as a layer 2 device. The real servers have their default-gateway set to the SVI address on the MSFC.


With routed mode vlan 10 and vlan 11 would use different IP subnets. The MSFC would have an SVI for vlan 10. The CSM is seen as a layer 3 device and would have an "interface" for both vlan 10 and vlan 11. The servers have their default-gateway set to vlan 11 interface on CSM.


So the client vlan is nothing to do with the actual end user machines as these may be spread across many locations.


Hope this makes sense.


Jon

Jon,


Thanks for your explanation, to put it in simple words then, the "client Vlan" is where the VIP for the server farm will be placed (vserver) and will have an SVI on the MSFC, the "server Vlan" is the Vlan where the real servers are located, these real servers will use the CSM for routing out of their subnet, correct?


Also, can the CSM automatically register each VIP in DNS if we configure it to do so or is this a manual entry in the DNS server?

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Jon Marshall Wed, 08/27/2008 - 09:11
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Borman


"the "client Vlan" is where the VIP for the server farm will be placed (vserver) and will have an SVI on the MSFC, the "server Vlan" is the Vlan where the real servers are located, these real servers will use the CSM for routing out of their subnet, correct?"


if you are talking about routed mode on the CSM then you are spot on.


As for DNS, no the CSM cannot automatically register a DNS name although the CSM can automatically inject/remove a VIP IP address into the routing tables - this may be some use in a failover situation. If you are interested have a look at reverse route injection in the CSM documentation.


If you want automatic DNS updates for VIPs then you need to look at something like the GSS (Global Site Selector) which can communicate with the CSM's and point requests to different VIPs based on their availability.


One last point. More than happy to help when i can but there is a more suitable forum to post into


"Data Centre" -> "Application Networking"


one of Cisco's experts on load-balancing frequents that group as well as quite a few other very experienced people.


But like i say, more than happy to help when i can.


Jon

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