confused about AAR...like many other VOIP people

[sead berberovic]

. This drives me crazy...I learned that when wan link is down or not enough BW, the route list would switch to, for example, PSTN-route group so everything is fine....and then later I read that in centrilazed CUCM (with locations-and not enough BW)) you have to enable AAR in order to switch to PSTN..WHY???..if my first statement is true, doesn't CUCM do it automatically? Where am I wrong?...thanks... 

[california]

you're talking about two different things when you use the route list they will be picked in order if the links are down.

so if your gateway is down then the next gateway on the route list will be picked automatically.

For AAR to work.  The gateway or link does not have to be down.   Your available bandwidth will dictate if it comes into play por not.

[Nadeem Ahmed]

When a call is made from the device of one location to the device of       another location, location bandwidth gets deducted from the maximum available       bandwidth that is available for the call at either location. If not enough       location bandwidth for the call exists at either location, instead of blocking       the call, Cisco Unified Communications Manager uses the table of AAR groups and       the external number of the terminating directory number to supply the alternate       number that is used to reroute the call through the PSTN or other network

so when link down does not comes into picture, its all have different concerpt and logic.

Br,
Nadeem 

Please rate all useful post.

[sead berberovic]

thank you guys....just to clarify. If I have:

RG-1 (WAN link)

RG-2(PSTN)

Scenario #1:  WAN goes down, CUCM picks RG2 and everything is fine.....

Scenario #2: Not enough BW, CUCM will NOT pick RG2, unless AAR is enabled

Is this OK...My problem was that I thought that Scenario#2 would work without enabling AAR....

Thanks again everybody....

[Nadeem Ahmed]

Correct!

Br,
Nadeem 

Please rate all useful post.

[sead berberovic]

thanks israel and nadeem....

[Chris Deren]

This is not correct, AAR is only triggered on CAC out of bandwidth, it has nothing to do with link failures. So, example 1 depends on where the trunks are but has nothing to do with AAR. Here you basically just rely on Route List/Route Group order and stop routing on user busy/unallocated service parameters.

Scenario 2 also depends on topology and where the GWs are located.

HTH,

Chris

[sead berberovic]

Hi Chris. Thanks for the reply....You'll be surprised to know how many voice people are struggling with the big (general) picture...and I believe that my question is a little confussing. i know that AAR is associated with CAC and lack of BW in centrilazed CUCM but what happens, for example, if:

1) in centrilazed CUCM,locations all default,AAR not enabled and not enough BW: will a phone be able to make a call at all/  or redial and connect (RL picks RG-Pstn).

2)same scenario but with multisite (each has its own CUCM) and not enough BW.......

Thanks everyone for your input....

[islam.kamal]

Hi Saed

1- RL : Route List includes more than RG and the RG can be "E1 , T1 , FXO ,etc..", so there is no need for AAR if you have only one site , you have redundant ways through PSTN . For example if your E1 is down , your FXO ports will handle calls.

2- Regarding AAR , If i have HQ and 2 branches and i have a WAN connection with limited bandwidth "Data,Voice and Video" and i need to limit the calls through my WAN . So i have to enable AAR to limit the number of calls , between sites , and when calls reach  the limit  , the call should go through PSTN way.

Thanks

please rate all useful information

[Chris Deren]

1. Where are the trunks?  AAR means you will be invoking calls that would normally go across WAN via local PSTN trunks, so who is calling what in your example and are the PSTN trunks centralized or local at the remote site?

2. Own CUCM?  Is it own cluster, just a sub?  Again, makes no difference as this has nothing to do with where servers are placed, but where PSTN trunks are located.

HTH,

Chris

[sead berberovic]

thanks everyone...I went a little deeper into this stuf in a last couple of days and now I am starting to understand it. Initially I never heard of AAR and when I finally did I was a little confused....

[Chris Deren]

Great, let us know od we can help any further.

HTH, Please rate all useful posts!

Chris

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