CCIE Voice Lab Preparation Notes #2

SRST
There are four SRST scenarios:

• SRST configuration for MGCP gateways
• SRST for H.323 gateways
• SRST for SIP gateways
• SRST on CME

1. MGCP Gateway

• Enables fallback for MGCP gateway
  router(config)#ccm-manager fallback-mgcp
• Enters SRST configuration mode
  router(config)#call-manager-fallback
• Configure Basic SRST settings
  router(config-cm-fallback)#max-dn value [dual-line] [preference preference-order]
  router(config-cm-fallback)#max-ephone value
  router(config-cm-fallback)#ip source-address ip-address
  router(config-cm-fallback)#system message primary message
  router(config-cm-fallback)#user-local country-code
  router(config-cm-fallback)#time-format [12|24]
  router(config-cm-fallback)#date-format format
  router(config-cm-fallback)#moh filename
  router(config-cm-fallback)#max-conferences value
  router(config-cm-fallback)#call-forward reason number
  router(config-cm-fallback)#voicemail number
  router(config-cm-fallback)#secondary-dialtone digit-string
• Configure the MGCP gateway as SRST reference in CUCM.
• Assign the SRST reference to IP phones by configuring corresponding device pool.
• The last step is to configure H.323 incoming and outgoing dial peers for SRST.
  

Additionally, you can use the router to provide multicast MOH to IP phones.

router(config)#ccm-manager music-on-hold

router(config)#call-manager-fallback

router(config-cm-fallback)#moh filename

router(config-cm-fallback)#multicast moh multicast-address route address-to-send-packets-to

2. SRST for H.323

On H.323 gateways, when the WAN link fails, active calls from Cisco Unified IP phones to PSTN are not maintained by default. Call preservation may work with 'no h225 timeout keepalive' command under 'voice service voip' 'h323' configuration mode.

3. SRST for SIP Gateway

SIP SRST feature is using Back-to-Back User Agent Mode.

By default, when configuring 'voice register global', it is SRST mode.

4. SRST on CME

router(config)#telephony-service

router(config-telephony)#srst mode auto-provision {all|dn|none}

Use none when configuring SRST with CUCM.

CCIE Voice Lab Preparation Notes #1

Understanding COR on Cisco IOS Gateways

• Calling privileges on IOS gateways are implemented using class of restriction (COR).
• COR lists contain CORs and are used to control call routing.
• COR lists are assigned to dial peers (Incoming COR List & Outgoing COR List).
• For each call, the incoming COR list is matched against the outgoing COR list. If the outgoing COR list is a subset of the incoming COR list, or no incoming COR list is configured, call is routed.

A COR is the building block of calling privileges. A COR list contains multiple CORs and is bound to dial peers. For CallManager Express, COR is applied to ephone-dns. For SRST, COR is applied to number range.

COR only takes in place when both incoming COR list and outgoing COR list are applied.

Normally, when configuring Outgoing COR list, we assign one COR to one Outgoing COR list, and the Outgoing COR list is analogous to the concept of Partition in CUCM, and the Incoming COR list is analogous to Calling Search Space.

Configuration Commands:

First, you need to define COR:

router(config)#dial-peer cor custom

router(config-dp-cor)#name COR-name

Then, you need to configure COR lists:

router(config)#dial-peer cor list list-name

router(config-dp-corlist)#member name

Lastly, you need to apply COR lists to incoming or outgoing dial-peers or ephone-dns.

router(config-dial-peer)#corlist incoming | outgoing list-name

router(config-ephone-dn)#corlist incoming | outgoing list-name

To apply COR lists to SRST ephones:

router(config-cm-fallback)#cor {incoming | outgoing} cor-list-name {cor-list-tag starting-number - ending-number | default}