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Section 5: Voice (6 Points)

  • Both phones should be able to ring each other using the numbers supplied. Use the most efficient method of transporting the voice from R1 to R4.

Did you jump straight in with Voice over IP (VoIP)? VoIP is not the most efficient means of transporting voice between R1 and R4 as they have a dedicated Frame Relay connection between them. If you were to use VoIP, the voice would have to be encapsulated into IP and then into Frame Relay before it is even transmitted. The most efficient method is therefore to encapsulate directly into Frame Relay using Voice over Frame Relay (VoFR). VoFR requires a map-class on the Frame Relay DLCI. Otherwise, it will break the existing data connectivity between R1 and R4, so pay particular attention to the commands, which must include frame-relay fragment and under the physical Frame Relay interface, you must configure the command frame-relay traffic shaping. The dial-peers for the remote site numbers simply point to the DLCIs between R1 and R4. Ensure you configure the command frame-relay voice bandwidth under the Frame Relay map-class on routers R1 and R4; otherwise, your voice will not work. This value could be calculated exactly using the standard voice codec g729r8 with associated overhead and the number of required calls but the question does not request this. If you configured this correctly as in Example 1-47 and Example 1-48, you have scored 3 points. If you succeeded in the VoFR but have broken the data connectivity, you have scored no points.

Example 1-47 R1 Voice and VoFR Configuration

interface Serial0/1
 frame-relay traffic-shaping
!
interface Serial0/1.101 point-to-point
 frame-relay  interface-dlci 101
  class ccie
  vofr cisco
!
map-class frame-relay ccie
 frame-relay fair-queue
 frame-relay voice bandwidth 64000
 frame-relay fragment
!
dial-peer voice 1 pots
 destination-pattern 01256
 port 1/0/0
!
dial-peer voice 2 vofr
 destination-pattern 01189
 session target Serial0/1 101

Example 1-48 R4 Voice and VoFR Configuration

interface Serial0/0
  frame-relay traffic-shaping
!
interface Serial0/0.1 multipoint
frame-relay interface-dlci 100
  class ccie
  vofr cisco
 no frame-relay inverse-arp
!
map-class frame-relay ccie
frame-relay fair-queue
 frame-relay voice bandwidth 64000
frame-relay fragment
!
dial-peer voice 1 pots
 destination-pattern 01189
 port 1/1/0
!
dial-peer voice 2 vofr
 destination-pattern 01256
 session target Serial0/0 100

  • Ensure that voice is still available if the main connection between R1 and R4 fails.

It is now time to configure VoIP, because if the Frame Relay network fails, you will need to run voice over the ISDN network between R1 and R4. The only method available to you is VoIP. Additional dial-peers are required each end pointing to the loopback IP addresses of each remote router. You must ensure that the VoFR is used before the VoIP so you will need to allocate a preference to the dial-peers. The lowest number dial-peers will have preference so it is advised that the VoFR dial-peers should be configured before the VoIP. Alternatively the VoIP dial-peers can have a priority manually configured higher than the default 0, which ensures if your dial-peer numbering is out of sync, the router still chooses VoFR before VoIP. Both methods of priority have been shown in the configuration for clarity. If you have configured this correctly as in Example 1-49 and Example 1-50, you have scored 2 points.

Example 1-49 R1 VoIP Configuration

dial-peer voice 3 voip
 preference 5
 destination-pattern 01189
 session target ipv4:10.4.4.4

Example 1-50 R4 VoIP Configuration

dial-peer voice 3 voip
 preference 5
 destination-pattern 01256
 session target ipv4:10.1.1.1

  • Make the phone on R1 also answer calls if 01962 is dialed on the R4 connected handsets; do not use number expansion to achieve this.

You are required to simply add additional dial-peers for 01962 on R4 (both VoFR and VoIP) pointing to R1, and then configure R1 with an additional dial-peer POTS pointing to the original FXS phone port, which currently contains 01256. If you have configured this correctly as in Example 1-51 and Example 1-52, you have scored 1 point.

Example 1-51 R1 01962 Configuration

dial-peer voice 6 pots
 destination-pattern 01962
 port 1/0/0

Example 1-52 R4 01962 Configuration

dial-peer voice 4 VoFR
 destination-pattern 01962
 session target Serial0/0 100
!
dial-peer voice 5 voip
 preference 5
 destination-pattern 01962
 session target ipv4:10.1.1.1

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