request for sample SRST configs - 3825

[George Banuelos]

Greetings,

Can someone please post sample(s) SRST router IOS config that can be used to build a 3825 to support Inbound DID calling under an SRST event?  The host cluster has 1 pub & 1 sub.  The 3825 has 2 PRIs. There are 4 VG224's & 1 2811 (used as an 8 port PLAR analog gateway) that would also need to call out during an SRST event.  Most IP phones (7942G and a couple 7971G) are provisioned using Extension Mobility. 

I understand that 'callmanger-fallback' type SRST is needed when Extension Mobility is used and that this method queries phones for their loaded profile during the re-registration procedure with the SRST router.  Does callmanager-fallback type support PLAR on a 2811?      

Also, can the 8 analog PLAR ports on a 2811 be configured to dial a different destination under an SRST event?  In other words, during normal operation, these PLARs call into a DN on the CUCM forwarded over the Unity server and under an SRST, they would need to dial out to the PSTN...

Would it be easier to configure 'telephony' SRST so that each phone receives respective DID assignements that match the Extension Mobility profiles?  Would this simplify PLAR set-ups for the 2811 during and SRST event?

Having a sample of both 'callmanager-fallback' and 'telephony' types would be appreciated.

Thank you!

- Psalm 116

[Jonathan Schulenberg · Accepted solution]

I understand that 'callmanger-fallback' type SRST is needed when Extension Mobility is used and that this method queries phones for their loaded profile during the re-registration procedure with the SRST router. 

Neither SRST mode is Extension Mobility-aware. As far as the router is concerned, whatever configuration the Device Profile applied to the phone IS the phone's configuration. Also, the phone tells the router during registration what DN(s) it has, not the other way around.

Here's a sample config for SCCP phones. Do *not* forget about the dial-peers needed to make outbound calls; this only gets phones to register.

call-manager-fallback
 max-ephones 25
 max-dn 100 dual-line
 ip source-address  port 2000 strict-match
 system message primary Survivability Mode Engaged
 max-conferences 4 gain -6
 transfer-system full-consult
 transfer-pattern .T
 call-forward pattern .T
 secondary-dialtone 9

Does callmanager-fallback type support PLAR on a 2811?

From the phones? No. From an FXO/FXS port? Yes because that is indepedant of the SRST configuration.

Also, can the 8 analog PLAR ports on a 2811 be configured to dial a different destination under an SRST event?

Not directly. You could probably make this work if you are *very* skilled with dial-peers. If the CUCM-facing outbound dial-peer is in a busyout state (e.g. SIP OPTIONS PING) you could have a POTS dial-peer with the same destination-pattern but a translation profile that changed it into a PSTN-dialable format. In addition to the skill level, this would require disconnect supervision to avoid the ports being left offhook indefinitely. In other words, ground-start or a PRI.

Would it be easier to configure 'telephony' SRST so that each phone receives respective DID assignements that match the Extension Mobility profiles?  Would this simplify PLAR set-ups for the 2811 during and SRST event?

No. Again, neither SRST mode is EM-aware and analog FXS/FXO ports are independant of the SRST configuration.

Please remember to rate helpful responses and identify helpful or correct answers.

[George Banuelos]

This feedback is very helpful, thank you.  It changes my previous understanding of SRST.  I had received comments in another SRST posting explaining that the callmanager-fallback type was needed for an Extension Mobility environment that required inbound calls to DID/DN (thank you for clearing this up, it caused me to review the previous posting and I actually made an assumption).  It was also explained (if I understood correctly) that the telephony-service option could actually be used to program the site's phones to 'override' the interrogation process and assign specific DNs to phones based on MAC - is this understanding correct?

The answers posted helped me determine that any PLAR will not be supported on IP phones. 

Can analog VG224 ports support PLAR during SRST?   

Are analog VG224 ports used as FAX lines supported during SRST?

Can inbound DID to DN on VG224 ports be supported during SRST?

It looks like moving the FXS cards (used for PLAR) from the 2811 over to the 3825 is a better solution during SRST, will this require the addition of a PVDM card to support a total of 8 FXS ports and 4 FXO ports on the 3825?

Currently the 3825 is an MGCP gateway off a hosted CUCM cluster... if the FXS & FXO cards are added to the 3825, will the IOS SRST config keep the FXS & FXO ports going?

The 3825 currently has 2 PRI's on it only - if 1 PRI is disabled, will the existing PVDM module be enough to support 1 PRI, 8 FXS ports, 4 FXO ports and the IP phones under SRST?

Per Cisco docs, the 3825 can support up to 300+ IP phones in SRST... how can the current capacity be determined for the 3825 in question - is this license based or is configuration based?

Thank you again for all your help...

- Job 38:36