/mcpAdvanced Call Routing Techniques Over the years as business needs grow, the company expands and requires more DIDs and enterprise administrators can find that the basic dial-peers do not meet scale well. There can be on-off situations that need to be addressed, or perhaps there are just too many dial-peers in general. Having thousands of dial- peers does not make administration and troubleshooting easy. Having a dial-peer for each specific CUCM server or call agent starts to compound the problem of too many dial-peers because now an administrator needs to configure a dial-peer for for each digit-string. If there is have more than one SIP provider connecting to a gateway, or a few different people using the same CUBE, this makes isolating a specific tenant very tough. Cisco has taken this feedback and created a set of items that can address these issues and more. Dial-peer Groups, Voice Class tenants, destination server-groups, e164-pattern-maps and POTS trunk groups allow for an administrator to solve all of the problems listed and many more not listed. Dial-Peer Groups Dial-peer groups were added in Cisco IOS 15.4(1)T and Cisco IOS-XE 3.11S and POTS dial-peers were added as an option in Cisco IOS 15.5(1)T and Cisco IOS-XE 3.14S. A dial-peer group allows administrators to specify an exact dial-peer for outbound routing based on the inbound dial-peer matched. Once an inbound dial-peer with a dial-peer group configured is matched, the call uses the dial-peer defined in the dial-peer group even if the destination-pattern does not match. The only prerequisite is the outbound dial-peer must be Up so an outbound matching method must be configured, however, this is not actually used to route the call. The best way to describe dial-peer groups is to liken them to the concept of static routes in a routing table. These are static inbound to outbound routing decisions that take away some of guesswork for the gateway because they are telling it exactly how to route the call. Full Documentation: Cisco Unified Border Element Configuration Guide - Cisco IOS XE 17.6 Onwards