Right-size the Expressway-C cluster for Mobile & Remote Access (MRA), B2B video, and traversal zones. Picks OVA profile, cluster size, and HA plan against your user count and call volumes.
Expressway-C lives inside the enterprise and pairs with Expressway-E at the edge for MRA and B2B video. It's sized by concurrent registered endpoints, traversal calls, and peak call setup rate — not just raw user count. This tool takes your numbers and returns the right OVA profile, cluster size, and HA requirement.
Set inputs, click Size Expressway-C.
Small, Medium, Large.
Node count for HA.
Registrations + calls headroom.
Zones, transforms, DNS.
Cisco ships Expressway-C in three OVA sizes. Small (2 vCPU, 4 GB RAM, 132 GB): up to 500 concurrent MRA registrations, 150 concurrent traversal calls, 100 BHCA. Medium (4 vCPU, 6 GB RAM, 132 GB): up to 2500 registrations, 500 traversal calls, 500 BHCA. Large (8 vCPU, 8 GB RAM, 132 GB): 5000 registrations, 1000 traversal calls, 1500 BHCA per node. Cluster up to 6 nodes for linear scale.
The common sizing mistake: counting users, not concurrent registrations. Users register from laptop + phone + tablet, so a 1000-user MRA deployment can easily hit 2500 registrations. Also, laptop Jabber in the background counts as registered even when nobody's on a call. Use 1.8-2.2× the user count as your registration estimate unless you know otherwise from real data.
Cluster size drives HA, not just capacity. A 2-node pair survives one node failing; a 4-node cluster survives two. For MRA, pair your clusters with Expressway-E pairs — C-to-E zones should never span different HA pairs without clear routing. Place nodes in different physical racks at minimum; different data centers if you have a DR plan.
No — they must be separate OVAs with separate IPs. Different security zones.
6 nodes. Above that, deploy a second cluster with DNS-based load balancing.
Yes for internal traversal. MRA requires the full C+E pair.
Standard ESXi works. DRS recommended. Don't over-commit CPU.
Single site.
Multi-site WAN.
3 regions.
Our UC Modernization Sprint deploys Expressway-C/E pairs with proper firewall rules, certs, and integration with CUCM + Webex.