C2900-universalk9-mz.spa.157-3.m4b.bin Jun 2026

Router# copy running-config tftp://192.168.1.100/backup-config.txt Router# copy flash:old-image.bin tftp://192.168.1.100/

This image supports the full suite of capabilities of the ISR G2, including:

Router# copy tftp://192.168.1.100/C2900-universalk9-mz.spa.157-3.m4b.bin flash: C2900-universalk9-mz.spa.157-3.m4b.bin

This release is part of the train, which introduced several important features for branch office routers:

Router# show version | include IOS

Understanding the anatomy of a Cisco IOS filename is crucial. The name C2900-universalk9-mz.spa.157-3.m4b.bin is not random; it follows a strict naming convention.

: Supports IPsec, SSL VPN, and advanced firewall capabilities. Note that certain weak ciphers, such as dhe-aes-256-cbc-sha , were removed in later 15.6(3)M+ releases to address security vulnerabilities. Router# copy running-config tftp://192

Here’s a concise write-up for the file , suitable for documentation, release notes, or inventory records.