Section 5: Voice (7 Points)

• Configure VoIP between R1 and R4 using the numbers supplied in Figure 3-10; ensure your VoIP is operational if the Frame Relay network fails.

A basic VoIP scenario, to ensure VoIP is operational in the event of Frame Relay failure, you simply need to point your session target IP addresses to the loopback interfaces on R1 and R4, which will still be reachable in the event of a failure over the ISDN. If you have configured this correctly as shown in Example 3-66 and Example 3-67, you have scored 2 points.

Example 3-66. R1 VoIP Configuration

 dial-peer voice 1 pots  destination-pattern 01256  port 1/0/0 ! dial-peer voice 01189 voip  destination-pattern 01189  session target ipv4:10.4.4.4 

Example 3-67. R4 VoIP Configuration

 dial-peer voice 1 pots  destination-pattern 01189  port 1/1/0 ! dial-peer voice 1256 voip  destination-pattern 01256  session target ipv4:10.1.1.1 

• Set up a hunt group on R4 so that if the number 01189 is dialed and voice port 1/1/0 is in use, port 1/1/1 answers the call. Port 1/1/0 should always answer the call if the phone connected to this port is not in use first.

To create a hunt group, you need to configure an additional pots dial-peer statement on R4 for the same number of 01189; by assigning preference values to each dial-peer you can manipulate which port answers the call first and that the secondary answers when the primary is in use. The lower the preference value is the higher the priority will be. If you have configured this as shown in Example 3-68, you have scored 2 points.

Example 3-68. R4 Hunt Group Configuration

 dial-peer voice 1 pots  preference 1  destination-pattern 01189  port 1/1/0 ! dial-peer voice 2 pots  preference 2  destination-pattern 01189  port 1/1/1 

• Define an order of preference for selecting a codec when R1 initiates a call to R4. R1 should first negotiate to use a g728 codec and then fall back to a g729r8 with a 20-byte payload. Leave the R4 codec as default.

By assigning a voice-class codec on R4's VoIP dial-peer, you can define which codec is used. If the first codec fails, you can define what the fallback codec is by assigning preferences. If you have configured this correctly as shown in Example 3-69, you have scored 3 points.

Example 3-69. R4 Hunt Group Configuration

 voice class codec 1  codec preference 1 g728  codec preference 2 g729r8 ! dial-peer voice 1189 voip  destination-pattern 01189  voice-class codec 1  session target ipv4:10.4.4.4