- Expansion module
- FXS/DID x 2 + FXO x 4
- for Cisco 4451-X; Integrated Services Router 4221
The Cisco 4000 series Integrated Services Routers (ISRs) host the Cisco network interface modules (NIMs), which have evolved from the enhanced high-speed WAN interface card (EHWIC), increasing port density and module capability. The NIMs support online insertion and removal (OIR), reducing the downtime required for new or replacement modules.