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New Member

two SRST gateways

I'm designing a centralized CCM/Unity solution for customer. On one of the remote site, we'll have two gateways both having the SRST capability. My question is: Are IP phones able to detect to SRST gateways?

Thanks

6 REPLIES
Cisco Employee

Re: two SRST gateways

The SRST gateway is configured as a backup call manager in the phones so when they loose touch with the central ccm, they will fallback to the SRST gateway, so , yes, the phones can detect the gateways, but only after it has been configured.

New Member

Re: two SRST gateways

I would run HSRP between both routers LAN interfaces out at your remote site. Make sure you have PSTN facilities in both boxes.

Phones do not necessarily "detect" their SRST devices....if IP phones fail to register with Pub/Sub and Teirch. CM's, then their last ditch effort is to attempt registration with their default gateway, which should be the SRST device.

Also, keep in mind, that in CM 3.3, you can specify a device other then the default gateway as your SRST gateway.

New Member

Re: two SRST gateways

I think I didn't make my question very clear. When I am saying there are two SRST routers,I mean both routers have T1ports to PSTN. Think about this case, when WAN goes down and caller from PSTN called in to SRST router A, but if IP phones didn't register their DID on SRST router A, they registere on SRST B.The router A for sure won't be able to transfer the call into that phone. So alternatively my question coule be how these two SRST routers have the DID and IP phone information? From CCM or from IP phone?

I appriciate the answers from you guys.

Thanks

New Member

Re: two SRST gateways

You could use Dial-peers with a high preference pointing at the other srst router.

Re: two SRST gateways

The way to do this is using Dial peers and manual configuration of the handsets. The phones do not automatically pick up the SRST reference unless it was their default gateway hence the need for manual configuration.

1.) configure the default gateway of half the handsets to router A

2.) configure the default gateway of the other half to router B

Make sure that when you do 1 and 2 you keep the numbers in blocks e.g. 100-123 on A and 124-146 on B

3.) configure Dial peers on the routers to point to the other router for the group numbers. e.g a dial peer on A that points to router B for 124-146 and a dial-peer on B that points to A for 100-123

4.) you may have to configure preferences as 2 for both the above dial-peers as they will be conflicting with the existing dial-peers fr incoming calls.

This should allow you to have calls come in on one router and be delivered to the other one during SRST.

If you don't do it by blocks then you'll just have more dial peer statements to type in.

Paul

New Member

Re: two SRST gateways

That'll be a great answer. After I reading your solution, I have one comment to share with you guys. DIDs actually are assgined with the coresponed T1 or maybe FXO line(has DID feature)by carrier, if I have two routers , I should've known which T1 or FXO line having what range DIDs, then we manually configure IP phones to that coresponded gateway(as you describered). In that case, we don't need dial-peer to the other router.

Thanks

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