SRST Configuration on the Cisco IOS Gateway ccsp training institute in india

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To configure Cisco Unified SRST on a Cisco IOS router to support the Cisco IP Phone
functions, follow these steps:
Step 1 Enter call-manager-fallback configuration mode to activate SRST.
Step 2 Define the IP address and port to which the SRST service binds.
Step 3 Define the maximum number of directory numbers to support.
Step 4 Define the maximum number of IP Phones to support.
Step 5 Define the maximum number of numbers allowed per phone type.
Step 6 Define the phone keepalive interval.
TIP When Cisco Unified SRST is enabled, Cisco IP Phones in call-manager-fallback
configuration mode do not have to be reconfigured, because phones retain the same
configuration that was used with CUCM.
SRST Configuration on the Cisco IOS Gateway 127
SRST Activation Commands
Example 6-1 shows the commands for the first two SRST configuration steps.
Example 6-1 SRST Activation Commands
RemoteSite#configure terminal
RemoteSite(config)#call-manager-fallback
R e m o t e $ i t e ( c o n f i g - c m - f a l l b a c k ) # i p source-address ip-address [port port]
[any-match I strict-match]
The Cisco IOS command call-manager-fallback enters call-manager-fallback configuration
mode.
The Cisco IOS command ip source-address enables the router to receive messages from
the Cisco IP Phones through the specified IP addresses and provides for strict IP address
verification. The default port number is 2000. This IP address will be supplied later as an
SRST reference IP address in CUCM Administration.
The ip source-address command is mandatory. The fallback subsystem does not start if the
IP address of the Ethernet port to which the IP Phones are connected (typically the Ethernet
interface of the local SRST gateway) is not provided. If the port number is not provided,
the default value (2000) is used.
The any-match keyword instructs the router to permit Cisco IP Phone registration even
when the IP server address used by the phone does not match the IP source address. This
option lets you register Cisco IP Phones on different subnets or those with different default
DHCP routers or different TFTP server addresses.
The strict-match keyword instructs the router to reject Cisco IP Phone registration attempts
if the IP server address used by the phone does not exactly match the source address. By
dividing the Cisco IP Phones into groups on different subnets and giving each group different
DHCP default router or TFTP server addresses, this option restricts the number of Cisco
IP Phones allowed to register.
SRST Phone Definition Commands
The commands shown in Example 6-2, max-dn and max-ephones, are mandatory because
the default values for both are defined as 0.
Example 6-2 SRST Phone Definition Commands
RemoteSite#configure terminal I
RemoteSite(config)#call-manager-fallback
RemoteSite(config-cm-fallback)#max-dn max-directory-numbers [dual-line]
[preference preference-order]
RemoteSite(config-cm-fallback)#max-ephones max-phones
128 Chapter 6: Implementing Cisco Unified SRST and MGCP Fallback
The Cisco IOS command max-dn sets the maximum number of directory numbers or
virtual voice ports that can be supported by the router and activates dual-line mode. The
maximum number is platform-dependent. The default is 0.
The dual-line keyword is optional. It allows IP Phones in SRST mode to have a virtual
voice port with two channels.
NOTE The dual-line keyword facilitates call waiting, call transfer, and conference
functions by allowing two calls to occur on one line simultaneously. In dual-line mode,
all IP Phones on the Cisco Unified SRST router support two channels per virtual
voice port.
The optional parameter preference sets the global preference for creating the VoIP dial
peers for all directory numbers that are associated with the primary number. The range
is from 0 to 10. The default is 0, which is the highest preference.
NOTE The router must be rebooted to reduce the limit on the directory numbers or
virtual voice ports after the maximum allowable number is configured.
To configure the maximum number of Cisco IP Phones that an SRST router can support,
use the max-ephones command in call-manager-fallback configuration mode. The default
is 0, and the maximum configurable number is platform-dependent. The only way to
increase the maximum number of Cisco IP Phones supported is to upgrade to a higher
hardware platform.
NOTE The router must be rebooted to reduce the limit on Cisco IP Phones after the
maximum allowable number is configured.
SRST Performance Commands
To optimize performance of the system, best practice dictates that you use the limit-dn and
keepalive commands, as shown in Example 6-3.
Example 6-3 SRST Performance Commands
RemoteSite#configure terminal
RemoteSite(config)#call-manager-fallback
RemoteSite(config-cm-fallback)#limit-dn {7910 I 7935 I 7940 I 7960} max-lines
RemoteSite(config-cm-fallback)#keepalive seconds
SRST Configuration on the Cisco IOS Gateway 129
The optional Cisco IOS command limit-dn limits the directory number lines on Cisco IP
Phones during SRST mode, depending on the Cisco IP Phone model.
NOTE This command must be configured during the initial Cisco Unified SRST router
configuration, before any IP Phone actually registers with the Cisco Unified SRST router.
However, you can change the number of lines later.
The setting for the maximum number of directory lines is from 1 to 6. The default is 6. If
any active phone has the last line number greater than this limit, warning information is
displayed for phone reset.
The optional Cisco IOS command keepalive sets the time interval, in seconds, between
keepalive messages that are sent to the router by Cisco IP Phones. The range is 10 to 65535.
The default is 30.
The keepalive interval is the period of time between keepalive messages that are sent by a
network device. A keepalive message is a message that is sent by one network device to
inform another network device that the virtual circuit between the two is still active.
NOTE If the default time interval between messages of 30 seconds will be used, this
command does not have to be used.
Cisco Unified SRST Configuration Example
Figure 6-4 shows a multisite topology that supports SCCP-controlled IP Phones at the
remote SRST site. The configuration is shown in Example 6-4.
Figure 6-4 Multisite Topology Supporting SCCP-Controlled IP Phones at the Remote SRST Site
Main Site
Linel; 2001 Linel; 2002 Linel: 2003
Line2:3001 Line2:3002 Line2:3003
130 Chapter 6: Implementing Cisco Unified SRST and MGCP Fallback
NOTE More commands might be necessary, depending on the complexity of the
deployment.