Cisco IOS Dial-Peers: Toll Bypass and Tail End Hop Off (TEHO)

Let’s investigate a scenario where a company has offices using a Cisco Unified Communications Manager Express (CUCME) router in San Jose, California and a CUCME system in New York City. The router in New York City will be configured to route 5 digit inter-office calls to the San Jose network over the IP WAN. If the IP WAN is not available, the router should be configured to re-route the call to the PSTN using 11 digit dialing to the direct inward dialing range 408-551-2XXX that was purchased from the PSTN provider. The following dial-peers are used to configure this call routing: Dial-peer voice 109 voip Destination-pattern 12… Preference 1 Session target ipv4:10.2.1.1 ! Dial-peer voice 209 pots Destination-pattern 12… Prefix 914085512 Preference 2 Port 0/0/0:23 ! Dial-peer voice 203 pots Destination-pattern 91[2-9]..[2-9]…… Prefix 1 Port 0/0/0:23 Some configuration details discussed in previous blogs have been omitted from this discussion so we could focus on the dial-peer hunting and digit manipulation involved in re-routing a call to the PSTN if the primary WAN path was to fail. All 5 digit patterns beginning with the digits 12 are routed to dial-peer 109 by default based on the lower preference. If dial-peer 109 cannot reach 10.2.1.1, dial-peer 209 the call will be re-routed over the PRI (port 0/0/0:23) without any end user intervention. Dial-peer 209 manipulates the dialed digits (called party) to an 11 digit pattern prefixed with a 9 access code. The new pattern matches dial-peer 203 and is routed to the PRI as an 11 digit pattern (access code is stripped). Using this configuration, calls will only be re-routed across the PRI if the destination IP address in unreachable. Call Admission Control (CAC) should be implemented using an H.323 gatekeeper to guarantee call quality. We will cover the Gatekeeper CAC configuration in a future blog. A Tail-End Hop Off (TEHO) dial-peer can be configured to enable toll cost savings for calls routed from NYC to local San Jose, California destinations on the PSTN. TEHO functionality is commonly referred to as least cost routing (LCR) which is enabled in dial-peer 401 below: Dial-peer 110 voip Destination-pattern 91408……. Prefix 91408 Session target ipv4:10.1.1.1 The CUCME device in San Jose must be configured with a dial peer similar to dial peer 203 to match on the 11 digit pattern prefixed with a 9 access code. The San Jose CUCM platform will normally route the call to the local PSTN gateway as a 7 or 10 digit local pattern (each LEC may have different regional requirements). In the next blog, we will investigate inbound and outbound call routing in sites where FXO analog ports are used to connect to the PSTN. We will then begin to explore the exciting world of translation profiles. REFERENCES Cisco IOS Dial Peer Features http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/dial_peer/dp_confg.html Global Knowledge Cisco Unified Communications classes www.globalknowledge.com/go/cisco Cisco Press Books – CVOICE / GWGK / TUC http://www.ciscopress.com/markets/detail.asp?st=44706