Cisco 300-830 CLCCE cheat sheet

Webex Calling is delivered from the Cisco Webex cloud; the customer keeps only endpoints, an optional local gateway for PSTN or legacy breakouts, and network connectivity, with call control hosted by Cisco.

Webex Calling offers two PSTN options: Cisco-provided PSTN (Cloud Connected PSTN via a provider) or Local Gateway (LGW) registration to a premises router for PSTN and emergency breakout.

Cisco Unified Border Element (CUBE) is the standard session border controller for SIP trunking and for connecting on-premises Unified CM to Webex or to a service provider; it terminates and re-originates SIP signaling and RTP.

Cisco Expressway-C pairs with Expressway-E to traverse firewalls for Mobile and Remote Access (MRA); Expressway-C sits inside the trusted network toward Unified CM, Expressway-E sits in the DMZ.

Mobile and Remote Access requires Unified CM IM and Presence or Expressway-based registration; endpoints register to Expressway-C using the traversal zone to Expressway-E, not directly to Unified CM.

Cisco Unified Communications Manager Cloud (UCM Cloud) is a Cisco-hosted dedicated Unified CM deployment; it is distinct from Webex Calling and is managed through the Cisco cloud operations portal.

Cisco Webex Edge Connect provides a private, SLA-backed connection from the customer network to the Webex cloud using a direct connect partner instead of the public internet.

Hybrid services (such as Hybrid Calendar or directory sync) use Cisco Expressway or a connector to link on-premises Unified CM data with Webex cloud services.

Cloud and on-premises coexistence uses a SIP trunk between Unified CM and Webex Calling or UCM Cloud; dial plan and numbering must be coordinated to avoid overlapping extensions.

MRA firewall rules: Expressway-E needs inbound TCP 8443 (or 443) from the internet for client registration, plus TCP 5060/5061 for SIP and UDP 3478 for TURN; Expressway-C to Expressway-E uses the traversal zone on TCP 7001.

Expressway-E in the DMZ uses a dual network interface: one toward the DMZ and one toward the internal network, with no direct routing between the two; the internal interface only reaches Expressway-C.

DNS is critical for MRA: external DNS must resolve the Expressway-E cluster FQDN to public addresses (SRV _collab-edge._tls), and internal DNS must resolve _cisco-uds._tcp for on-premises discovery.

Certificate requirements: Expressway-E presents a certificate signed by a public CA matching the cluster FQDN; Expressway-C and Unified CM use CA-signed certificates with the correct SANs for the traversal and neighbor zones.

Quality of Service: mark voice RTP EF (DSCP 46), call signaling CS3 (DSCP 24), and video AF41 (DSCP 34); trust boundaries must be configured so markings survive the WAN.

NAT traversal for SIP uses ICE/TURN/STUN; Expressway-E provides TURN relay for MRA media when endpoints are behind NAT.

Bandwidth planning: G.711 is about 80 kbps per call with overhead, G.729 about 24-30 kbps, and Opus adapts; video calls require substantially more, so size WAN links per concurrent call counts.

Cloud connectivity for Webex Edge Connect uses a direct connect partner with BGP peering to the Webex cloud; the customer advertises only the internal subnets that need to reach Webex services.

High availability at the edge uses Expressway clusters with up to six peers; Unified CM uses clusters with a publisher and subscribers, and endpoints should have a defined registration fallback order.

Unified CM call routing order: translation pattern, then route pattern (with digit analysis), then route list, then route group, then gateway or trunk; the first matching pattern in the partition search space wins.

Partitions and calling search spaces (CSS): a CSS is an ordered list of partitions; a device or line uses a CSS to define which partitions it can dial, and line CSS overrides device CSS for calls originated by that line.

Digit analysis uses the most specific match: exact digits beat wildcards, and among wildcards the one with fewer wildcards and more specific digits wins; a route pattern with @ matches full E.164 numbers.

Route lists provide failover: the first route group is tried, and if all its devices are unavailable, the next route group is used; route groups select gateways by order or by top-down distribution.

Translation patterns rewrite digits using discard digits (predot, preat, strip) and calling/called party transformation masks; they can also set the CSS for the transformed call.

Globalized dial plan: normalize all numbers to E.164 at the ingress edge with translation patterns, then apply site-specific transformation masks at the egress gateway to present local formats.

Survivable Remote Site Telephony (SRTS) on IOS gateways provides local call control fallback when the WAN to Unified CM is lost; the gateway registers as an SRST reference for the site's endpoints.

Hunt groups distribute calls to line members with algorithms such as longest idle, circular, and broadcast; hunt pilots use a partition and CSS for routing.

Dial peers on IOS gateways match inbound and outbound calls with destination patterns; preference values break ties, and voice translation rules can rewrite numbers per direction.

SIP security: use TLS for signaling and SRTP for media; Unified CM and Expressway support secure profiles, and MRA uses TLS 1.2 for the traversal link by default.

Certificate trust: Unified CM uses tomcat and callmanager certificates; Expressway uses server and client certificates for traversal; expired or mismatched SANs cause registration and zone failures.

Expressway troubleshooting: check zone status (Active/Inactive), the traversal zone, and the SIP status; 'zone not active' usually indicates a certificate, DNS, or firewall issue.

Unified CM troubleshooting: use RTMT for alarms and performance counters, the Dialed Number Analyzer (DNA) to simulate call routing, and the Call Detail Records (CDR) for post-call analysis.

Common MRA failures: incorrect external DNS SRV record, missing public certificate SAN, blocked TCP 8443 or UDP 3478, and untrusted certificates between Expressway-C and Unified CM.

Webex Control Hub provides analytics, troubleshooting, and device management for Webex Calling; call quality data uses MOS and jitter/latency metrics.

Log collection: Expressway has diagnostic logging and packet capture on the CLI; Unified CM uses RTMT trace and log central, and CUBE uses 'debug ccsip messages' for SIP flows.

Security hardening: disable unused services on gateways, use secure SIP profiles, enforce strong passwords, and restrict management access with ACLs and role-based access.