See this document for details on how call routing works in IOS. In Depth Explanation of Cisco IOS and IOS-XE Call Routing
If you need specific help on this topic please share detailed information, like the running configuration in your gateway and applicable call routing details from CM.
If i understood your problem correctly, In your case both connections are terminated on a single voice gateway. Easiest option what i suggest is to add a extra digit when sending the calls from CUCM to gateway, create dial peer matching those pattern and choose the right Connection( PRI/ SIP). This is to differentiate the calls based on deskphones as all calls are through same gateway and you want to choose SIP/PRI based on the calling
Other options is to match the dial peer based on the calling number type and process it.
Incoming called number matches the called number, what you are describing if I understood correctly is that you'd want to differentiate the call path based on who is making the call, ie calling number. To do that you need something like this.
dial-peer voice 45 voip
description From CUCM to GW PRI
answer-address 8...$
dtmf-relay rtp-nte sip-notify sip-kpml
dtmf-interworking rtp-nte
codec g711ulaw
no vad
Repeat this on another DP that matches the 5 digit extensions. Worth mentioning is that you need to make sure that you have no overlap between the two extension ranges, ie both cannot start with an 8.
Apart from this you also need to have something that sends the call outbound from the gateway and set this to be used based on the different matched inbound dial peers. For that I would recommend that you look at the document that I shared earlier and use DPG, Dial Peer Groups, as that sets the outbound dial peer to use based on the matched inbound. It could look something like this.
voice class dpg 1
description Dial-peer Group for PRI
dial-peer 10 !As we do not know what DP you have defined for the PRI this is just an example. Modify the number to match the DP you have.
dial-peer voice 45 voip
description From CUCM to GW PRI
answer-address 8...$
dtmf-relay rtp-nte sip-notify sip-kpml
dtmf-interworking rtp-nte
codec g711ulaw
no vad
destination dpg 1
dial-peer voice 10 pots
description Use PRI for PSTN calls
! add all the rest of the needed config to send calls to PRI
Not for the outbound direction to PSTN as you have nothing that states that if the call matches inbound on dial peer 45 that is needs to use dial peer 23 as the outbound. Add this to set it to use DPG for the outbound dial peer selection.
voice class dpg 1
description Dial-peer Group for PRI
dial-peer 23
dial-peer voice 45 voip
destination dpg 1
dial-peer voice 23 pots
destination-pattern BAD.BAD ! With DPG the actual destination patten is not used, but is still needed for IOS to see the dial peer as in an operational state. That's why you'd often see something like this used in configuration examples
Apart from this I would also strongly advice you to not use the same dial peer as both inbound and outbound as that has a tendency to mix up things. For that I would suggest that you make changes along the line with this, please note as you have only shared parts of your dial peer configuration you'd need to look at if this would fit into you're current configuration.
dial-peer voice 23 pots
no incoming called-number 8[0-5]..$ Incoming Dial-Peer
description Outbound calls to PSTN on PRI
tone ringback alert-no-PI
!
dial-peer voice 100 pots
tone ringback alert-no-PI
description Inbound calls from PSTN on PRI
incoming called-number .
direct-inward-dial
!
voice class e164-pattern-map 1
description E164 Pattern Map for called number to CUCM
e164 8...$
e164 <add the number range for 5 digits>$
!
dial-peer voice 22 voip
no destination-pattern 8...$
destination e164-pattern-map 1
