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MRA multi cluster deployement

we have a cluster in US of call manager and there we have VCS-C and E cluster as well, we use that for MRA and we want a similar setup for our users that belong to our another cluster in UK. For that we are in process of deploying another Expressway-C and E pair and we have read ILS is a prerequisite to know user’s home cluster details between the cluster. So my confusion is


1.let’s say am the user that belong to UK cluster, email , it will query _collab_edge to domain and it will hit our VCS-E in US and ultimately the cucm cluster in US then with ILS being enabled it will find the user’s home cluster details so at what point our London infrastructure that we are in process of deploying will come into picture? (new Exp-C and Exp-E) there a way we can force UK cluster users to hit UK cluster Exp-C and Exp-E for the same domain i.e., if yes, then what would be the role of ILS which is a prerequisite for MRA multiple cluster deployement.


Jaime Valencia
Hall of Fame Cisco Employee

1 At no point those new expressways will be used, traffic will be from US expressways to UK CUCM cluster for that scenario.

2 Geo DNS can point to their closest point of access (no matter if they're US or UK users), but if you want to force users to use only their expressways, you'd need subdomains. and so they're forced to use a single point of entry.



if this helps, please rate

are you talking about this?Capture1.JPG

Jaime Valencia
Hall of Fame Cisco Employee

No, that's different domains



if this helps, please rate are you saying(for a UK cluster user) if we keep just so obviously the flow would be towards US VCS-e and then ultimately to US cucm and from their it will leverage ILS to register the user to UK cluster?


2. if we want to force the user to connect to the local VCS-e and then from their to their home cluster so we will have to create subdomains like and another set of _collab_edge pointing towards and for that GeoDNS would be required correct (don't have much idea about it) , so can you provide me bit more details on this so that i can take this forward on how to leverage our UK expressway way pair of UK based users and not let the traffic flow to US



Jaime Valencia
Hall of Fame Cisco Employee

1 Endpoints will register to where the _collab-edge SRV points to, if it's a multi-cluster deployment then it will reach the CUCM via _cisco-uds, will determine if it's a local user, if not, will find the cluster where the user lives via ILS, and tell EXP-C to reach out to that cluster for registration.


2 No, that's not GEO-DNS, do a little a bit of research to find out what I'm talking about.



if this helps, please rate

so, coming to your 1st point so once the home cluster of a UK user is found using ILS, it will require EXP-C and probably a neighbor zone to UK cucm for it to register to UK cucm cluster?

won't just ILS be enough  since it keeps all the updates of cluster in ILs topology including home cluster


secondly, i dont know how subdomains is possible for our environment -since all users loginto jabber using so _collab_edge will always wuery the domain which will then take it o US VCS-E which we want to avoid

If you do use Geo_DNS I recommend using, they were the only ones that could do the SRV setup according to the SRND. We use them and now our MRA works consistently for our US and EMEA cluster.

We do not use subdomains since we did not want to make things more confusing for the end user login. Everything is a single domain and Callmanager uses ILS to find the users "Home Cluster".

so tell me one thing-

if we use GEO-dns that i need to research about then the request would be source to local VCS-E first then local VCS-C and local cucm then what is the point of having ILS if GEO-dns is supposed to route the request based on user's location, and does it mean GEO-dns enables having two collab_edge records pointing to different VCS-E cluster? since we already have it for for our US users and if GEO-DNS does the routing based on location and we use a single domain to login to jabber then it would obviously require a record to point to UK VCS-E

i think this is the solution


but not sure what it means when they says



To solve this, we utilize GEO DNS to located the end user’s IP range and match that to a region and then deliver a customized set of DNS SRV records to the client"
end user's IP range?

Yes that's why we use them...they were the only ones that could do it exactly as listed in the SRND. Other places wanted to use CNAME which caused some issues.

Yes, the end user's IP range (WAN address) tells them where they are located. Which "GEO" is the end user located. So if I'm at a Starbucks in Atlanta, Ga then I use the US expressway via GEO-DNS SRV and if I'm at a Coffee Shop in Germany, then I use the EU expressway based off the geo-dns SRV return from my IP (WAN) address.



How this WAN range would be determined for one geographic region? won't it be a random one?

 have a question, for short term we want to deploy a solution like this

We have a VCS-C and E cluster pair tied to our US cucm cluster with MRA working, we have another cluster in UK with CuCM and with our Geo DNS plans in the horizon for long term, for now we want to set up TCT and BOT devices for our UK based user in UK cucm cluster so correct me if this will work the way am thinking

1. since we have VCS-C and E pair setup with all SRV records for our domain
2. once the user logs in to jabber from outside , public DNS will take him to US VCS-E
3. From there it will ultimately reach the US cucm node where will turn ON ILS
4. With ILS on it should learn user's home my confusion lies here

1.With ILs on will it be able to redirect the request to UK cucm to look for user's TCT or BOT device for registration? or will it require some config on VCS-C and E as well.

2. if we have 6 VCS-C nodes will it support 2500X6 registrations, how does that work

#2 - Clusters support up to max 10,000 registrations (2500/node), so with 6 total you have N+2 redundancy
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