Configuring Cisco Routers to Support VoIP
Consider Figure 2-5 as a precursor to reading about the configuration of a
router with FXO, FXS, and VoIP neighbors.
Figure 2-5 Voice over IP Network Topology
CCNP ONT
[ 262 ] CCNP ONT Quick Reference
FXO FXS
FXS
B
A
PSTN
Example 2-1 Configuration of Router A
hostname router_A
interface s0/0
ip address 172.21.77.1 255.255.255.0
dial-peer voice 1 voip
destination-pattern 720
session-target ipv4:172.21.77.2
dial-peer voice 2 pots
destination-pattern 721
port 1/0/0
dial-peer voice 3 pots
destination-pattern 9
port 2/0/0
In Example 2-1, the dial plan consists of three patterns: Dialing 9 gets an
outside line, dialing 720 rings the phone on the other router, and 721 rings
the pots line on the local router.
All patterns need a destination-pattern statement to configure the dial plan.
Phones reached over IP also need a session target, whereas directly attached
analog phones are referenced by port.