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NetScaler ADC: GSLB: Static Proximity backup method


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Hi, 

 

according to the documentation, the backup method of static proximity will be used, when static proximity fails.

 

As the database is local, I have no clue how the fail is happening, in addition I have the following question:

 

I have 3 Sites, where 2 sites are in the same DMZ. The same DMZ sites are logically matching to the same country code, so I wonder how the NetScaler decides which one of them to pick?

Will it use its backup method to judge whether to go to dmz site1 or site 2, if the country code is defined for this county?

 

Kind regards

 

Mark

 

 

 

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Apologies if this isn't exactly the question you asked.

 

If your primary gslb method is staticproximity, your backup method (for static proximity) is one of the other methods:  roundrobin/leastconnection/leastresponsetime/sourceiphash/leastbandwidth/leastpackets/RTT/customload.  Roundrobin is default lb method.

 

Meaning, if a client comes from an IP for which a mapping can't be identified (no entry or not part of the subnet ranges you defined), it will fallback to gslb roundrobin or some other method as indicated.

 

Your static proximity entries should have non-overlapping criteria like country.subcriteria so they don't have the exact same matches (additional link below).

The match failure might be related to wildcard handling:  https://support.citrix.com/article/CTX232884

And while its not always easy to find there are some articles on the netscaler's built in geolite database.  That may help you understand the default entries, or you can create your own. 

 

However, if you're gslb is in active/passive config, then all requests go to datacenter1 unless its down and then they go to datacenter2 anyway (regardless of lb method).

Example:  gslb_vsrv_primary only maps to a single gslb_svc_primary with a backup gslb vserver bound pointing to gslb_vsrv_secondary/gslb_svc_secondary.

IF active/active load balancing, the staticproximity would be used to decide between locations; if unable to resolve, then roundrobin (or other backup method) would determine decision.

 

And in your later post:  yes,  you can use custom static database entries:

https://docs.citrix.com/en-us/netscaler/11-1/gslb/configure-static-proximity/add-custom-entries-static-proximity-db.html

(Its not a great example, but there is one in the admin guide.)

Carl's examples is more detailed in his gslb section (search for static or custom entries and go a few entries down):  https://www.carlstalhood.com/global-server-load-balancing-gslb-netscaler-12/

 

For advanced scenarios, content switching + gslb can help with some of the proximity decisions too:  https://nerdscaler.com/2017/06/15/cascaded-hierarchical-gslb-config/

 

 

 

 

 

Edited by Rhonda Rowland
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Hello,

 

I like to explain a bit more our situation:

 

I have 3 sites in my GSLB (A, B, C).

 

Site C is new and should be used for VPN only, while A and B also run some ADC.

 

We use static proximity / geo ip for a couple of the gslb services.

This includes our VPN configuration, where we have nodes in all sites,

This is working quiet well.

 

But we also have a ADC service using static proximity that only exists in Site A and Site B.

 

What happens for users that are identified as Site C users?

From what I see right now they get somehow moved to Site A and Site B, but I wonder if it is just performing round robin here, or if it is done using the backup method?

 

The GSLB Content Switching article looks promising to me, but first of all I would know whether my situation already matches the backup method or what is exactly happing there? :) 

 

Addition:

 

I just realized I can add multiple preferred locations to a Preferred Location list.

The (?) says: "The location list in priority order used for the given action."

 

Currently this looks for me like

 

add dns action act_gslb_pref_de GslbPrefLoc -preferredLocList "*.DE.*.*.*.*"
add dns action act_gslb_pref_es GslbPrefLoc -preferredLocList "*.ES.*.*.*.*"
add dns action act_gslb_pref_it GslbPrefLoc -preferredLocList "*.IT.*.*.*.*"

 

Let's say :
Site A is DE,
Site B is ES,
Site C is IT

 

Would the following just solve my dillemata for the service which is not existing in Site C?

set dns action act_gslb_pref_it GslbPrefLoc -preferredLocList "*.IT.*.*.*.*" "*.DE.*.*.*.*"

 

So, if there is no GSLB Service in IT but in DE, it will use Site A as a preference for the service?

 



Best regards

 

Mark

 

 

 

Edited by Mark Nickolai
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