IP-IP GW Configuration Notes for OCS to CUCM Connectivity

Some time ago I wrote a document that Microsoft went on to release to a few companies for pilot. The document outlined the configuration for Cisco/Microsoft integration using the IP-IP GW concept. This is a reprint of some updated content here that should also hold true for OCS R2 and all versions of CUCM.
One of the important elements for this integration is the version of IOS for the Cisco router. Although no version of IOS is bug free, 12.415xz has proven to be stable and relatively bug free in most situations. The following IOS command line example is based upon 12.4.15xz which has features found in other versions but without some of the bugs from later version like 12.4.20t.

The configuration below gives some typical NANP dial peers. You may also want to include dial peers for international and 911. Depending on your normalization in OCS your dial peers will of course vary. One thing to note, is IOS (12.4.15xz)there is no need to specify the + sign for incoming or outgoing dial peers as this version automatically strip the +. This also means no need to modify the mediation server to remove the plus either. This example follows the diagram depicted with different version of CUCM with 5.x (this can also be 6.x) using SIP and 4.2.3 using H323. For the version using SIP (5.x) you will need to configure MTP resources in CUCM and mark them as required. For CUCM using H323 only the gateway configuration is required, MTP resources are not required. In follow up entries, I will talk more about CUCM configuration for using H323 or SIP in both versions.
!
voice service voip
no notify redirect ip2ip
allow-connections h323 to h323
allow-connections h323 to sip
allow-connections sip to h323
allow-connections sip to sip
supplementary-service media-renegotiate
supplementary-service ringback h225-info
fax protocol t38 ls-redundancy 2 hs-redundancy 2 fallback none
h323
emptycapability
no h225 timeout keepalive
h245 passthru tcsnonstd-passthru
sip
midcall-signaling passthru
bind control source-interface FastEthernet0/0
bind media source-interface FastEthernet0/0
!
!
voice translation-rule 103
rule 1 /^\([2-9].........\)/ /+1\1/
rule 2 /^\(...........\)/ /+\1/
rule 3 /^\(...........\)/ /+\1/
!
!
voice translation-profile AddPlusForOCS
translate calling 103
!
!
sccp local FastEthernet0/0
sccp ccm X.X.X.X identifier 2 version 4.1
sccp ccm X.X.X.X identifier 1 version 4.1
sccp
!
sccp ccm group 1
description SCCP CCM group
bind interface FastEthernet0/0
associate ccm 1 priority 1
associate ccm 2 priority 2
associate profile 101 register MTP_5.x
!

!
dspfarm profile 101 mtp
codec g711ulaw
maximum sessions software 100
associate application SCCP

!
!
dial-peer voice 101 voip
description incoming SIP dialpeer
session protocol sipv2
session transport tcp
incoming called-number [2-9]..[2-9]......
dtmf-relay rtp-nte
codec g711ulaw
no vad
!
dial-peer voice 555755 voip
description to OCS Mediation server
translation-profile outgoing AddPlusForOCS
destination-pattern 1555755[23678].
session protocol sipv2
session target ipv4:X.X.X.X
session transport tcp
dtmf-relay rtp-nte
codec g711ulaw
ip qos dscp cs3 signaling
no vad
!
dial-peer voice 111 voip
description to Callmanager 5.x or 6.x FIRST SUBSCRIBER
preference 1
destination-pattern 1[2-9]..[2-9]......
session protocol sipv2
session target ipv4:X.X.X.X
session transport tcp
dtmf-relay rtp-nte
codec g711ulaw
no vad
!
dial-peer voice 112 voip
description to Callmanager 5.x or 6.x SECOND SUBSCRIBER
preference 2
destination-pattern 1[2-9]..[2-9]......
session protocol sipv2
session target ipv4:X.X.X.X
session transport tcp
dtmf-relay rtp-nte
codec g711ulaw
no vad
!
dial-peer voice 113 voip
description to Callmanager 4.X FIRST SUBSCRIBER
preference 3
destination-pattern 1[2-9]..[2-9]......
session target ipv4:X.X.X.X
dtmf-relay h245-alphanumeric
codec g711ulaw
no vad
!
dial-peer voice 114 voip
description to Callmanager 4.X SECOND SUBSCRIBER
preference 4
destination-pattern 1[2-9]..[2-9]......
session target ipv4:X.X.X.X
dtmf-relay h245-alphanumeric
codec g711ulaw
no vad
!
!
!
gateway
timer receive-rtp 1200
!
sip-ua
timers connection aging 120
!

The IP-IP GW is a handy piece of software embedded in IOS code. The IP-IP GW can also serve the dual purpose of terminating T1/E1 along with the already mentioned functionality. It can also connect OCS to other PBX’s not capable of SIP. Of course this isn’t the only device capable of bridging the gap and now with direct SIP a small network would probably steer away from this idea altogether. Places where this architecture may suit are larger deployments where connectivity to multiple PBX’s is a requirement. The current limitation for a mediation server to connect only to one gateway is the main reason we stayed with the IP-IP GW. The required MTP resources required by CUCM can also prove somewhat of a pain unless your entire CUCM deployment is based on SIP. Using H323 can remove some of the configuration complexity when this is the only part of your CUCM deployment that is required to use SIP.

I will be posting follow-up CUCM configuration notes in the coming days, so stayed tuned.