16.8 Considerations When Using Globalized Call Routing

This topic describes what needs to be considered when using globalized call routing.

Cisco IOS internal SAF clients have limited support for the + sign when advertising patterns:

  • Solution for PSTN backup of internal directory number:
    1. Advertise PSTN backup number in E.164 format without +.
    2. Add + by translation pattern used for AAR calls to numbers that do not start with +.
Cisco IOS Configuration DN Pattern and ToDID Limitation
profile dn-block 1 alias-prefix 1972555 pattern 1 type extension 4XXX 4XXX 0:1972555
  • The + is not supported in alias-prefix or extension.
  • PSTN backup cannot be advertised with +.
profile dn-block 2 pattern 1 type global 14087071222 +14087071222 (no ToDID)
  • The + is added to patterns configured with type global.
  • Global patterns always have ToDID unset.
  • There is no PSTN backup for global patterns.

Cisco IOS internal SAF clients have limited support regarding the plus sign (+) in advertised routes. In fact, the + sign cannot be configured in either the DN pattern or the ToDID rule. The only way to advertise a pattern with the + sign is to use the pattern tag type global command instead of the pattern tag type extensioncommand. In this case, however, the ToDID is always unset, regardless of the configured alias prefix at the directory number block profile.

When a CCD-enabled Cisco Unified Communications Manager uses globalized call routing for PSTN access, the mentioned limitation of Cisco IOS internal SAF clients causes issues because the backup PSTN number is not in a format that Cisco Unified Communications Manager can route to the PSTN.

The workaround is to make sure that CCD PSTN backup calls can be routed to the PSTN even if the number that results from the ToDID rule does not start with the + sign.

Note

Cisco IOS Software has limitations only in advertising patterns that include the + sign. Cisco IOS Software can process received patterns that include a + sign without any problems or limitations.

Solution for PSTN Backup Advertised in E.164 Format Without Leading +

This section describes the workaround for CCD PSTN backup calls to PSTN destinations that are in E.164format without a + prefix.

It would be very cumbersome to add all possible E.164 numbers to the overall dial plan of Cisco Unified Communications Manager. However, because CCD PSTN backup calls are always placed with the use of theAAR CSS of the calling phone, you can add one translation pattern ! to a partition that is accessible from the AAR CSS only. At that pattern, you can prefix a + to the called-party number and set the CSS of the translation pattern to a CSS that has access to the global PSTN route pattern (\+!).

That process solves the issue with CCD PSTN backup calls. However, if AAR is enabled, prefixing a + will break AAR, assuming that the AAR implementation is based on globalized call routing. If the external phone number mask of the destination phone is in E.164 format with a + prefix, then AAR calls would not work anymore because AAR calls use the same CSS and therefore would also match the ! translation pattern that prefixes a +. In this case, AAR calls would be placed to E.164 numbers with two + signs. To also make AAR CSS calls work, you must add a second translation pattern in the same partition that is accessible from the AAR CSS only. This second translation pattern \+! is not configured with any digit manipulation but uses the same CSS as the other translation pattern (!). As a consequence, AAR calls are passed on to the \+! route pattern without any digit manipulation (by matching the more specific \+! translation pattern, which does not prefix a +). CCD PSTN backup calls do not match the \+! translation pattern and are therefore routes.

Note

The described solution is a workaround only. The implementation of advertised patterns in Cisco IOS Software may be changed in the future so that + can be configured in the advertised pattern and in the ToDID rule. If so, you should change from the described workaround to the solution that allows CCD PSTN backup calls to be placed to globalized numbers.

TEHO Considerations

This section describes how CCD can be used to advertise TEHO routes.

  • TEHO destinations are located at the PSTN and do not exist internally.
  • Advertised hosted DN is PSTN destination and not internal DN.
    1. If SAF-learned TEHO route becomes unavailable, ToDID number is used for automatic backup call.
    2. Typically, both numbers are identical (ToDID rule is 0:) and use +E.164 format.
  • If no ToDID is advertised, call fails until learned TEHO route is completely removed.
  • Learned route is removed only after expiration of CCD PSTN Failover Duration timer (default: 48 hours).
  • Cisco IOS Software can advertise + only in global patterns (which do not support ToDID).
  • Avoid the use of global patterns in Cisco IOS Software.
    1. If + is required for TEHO implementation and local backup is desired, do not advertise TEHO routes at sites that use internal SAF clients.

TEHO destinations are located at the PSTN only; they do not exist internally at all. The advertised directory number is a PSTN number. When globalized call routing is enabled, this number must be in E.164 format with a + prefix.

Calls to PSTN destinations will match the learned directory number and are therefore sent to the TEHO site over the IP WAN. If the IP WAN is down, the local gateway should be used as a backup. This situation requires a ToDID rule of 0:. With this rule, the CCD PSTN backup number is identical to the learned directory number. When the IP path is marked as unreachable, the same number would be called using the AAR CSS of the calling phone.

Check the Use Hosted DN as PSTN Failover check box in Cisco Unified Communications Manager to generate a ToDID rule of 0:. In Cisco IOS Software, you cannot set the ToDID to 0:.

In addition, if globalized call routing is used, you are forced to use global patterns, which do not allow you to advertise any ToDID rule.

When a TEHO pattern is advertised without a ToDID rule, the local TEHO backup does not work. You can configure only static local backup routes by putting similar patterns into partitions that are listed later in the phone CSS. However, such patterns are used only after the learned pattern has been purged completely. By default, this process occurs after the expiration of the CCD PSTN Failover Duration timer, which is 48 hours by default.

Based on these issues, it is recommended that you not advertise TEHO patterns from Cisco IOS Software if the + is required and local backup is desired.