An introduction to Cisco IOS version 15

Developed for wide deployment in the world’s most demanding enterprise, access, and service provider aggregation networks, Cisco IOS Software Release 15 M and T provides a comprehensive portfolio of Cisco technologies, including the leading-edge functionality and hardware support from Releases 12.4 and 12.4T.

Release 15 M and T key innovations span multiple technology areas, including Security, Voice, High Availability, IP Routing and Multicast, Quality of Service (QoS), IP Mobility, Multiprotocol Label Switching (MPLS), VPNs, and Embedded Management.

Release 15 M and T provides customers new feature release delivery and hardware support in a shorter amount of time, broadened feature consistency, more reliable new feature release and rebuild schedules, proactive release support lifecycle policies, and easier software selection, deployment, and migration guidelines.

15 M (Extended Maintenance) releases delivered on a more frequent basis (approximately every 16 months), enabling customers to qualify, deploy, and remain on a release longer with active support. Release 15.0(1)M (FCS November, 2009) is the first 15 M release.
15 T (Standard Maintenance) releases (in between 15 M releases) ideal for the very latest features and hardware support before the next 15 M release becomes available. Each 15 T release receives bug-fix rebuild support for 13 months, plus an additional 6 months support for security/vulnerability issues such as Product Security Incident Response Team (PSIRT) advisories. Release 15.1(1)T (FCS March, 2010) is the first 15 T release.


Release numbering schemes for release 15M&T:



Maintenance rebuild methodology for release 15M&T:


Cisco IOS Software Release 15M&T Lifecycle:

Milestone Definition Date
First Customer Shipment (FCS) The date the software release is first available to customers on Cisco Software Download Center Day 0
Maintenance Deployment Point (MD Point) Maintenance Deployment (MD) designated M Releases are widely deployable, as proven through extensive system testing, which continues as part of Cisco’s ongoing commitment to improve and increase reliability and quality. A set of stringent criteria is used to analyze the quality of the release, such as high customer satisfaction, expansive customer deployment, demonstrated software reliability, and rigorous ongoing testing. Typically 9 to 12 months (3rd or 4th maintenance rebuild) after the initial posting (FCS date) of the release on Software Download Center
End of Sale Date (EoSale) The day the release is no longer orderable or included in manufacturing shipments of Cisco hardware. Approx. 28-30 months after FCS date
End of Software Maintenance (EoSM) This is the last date that Cisco Engineering may release any final software maintenance releases or software fixes for the release. Approx 40-42 months after FCS date


The benefits of Release 15M&T over Releases 12.4 Mainline and 12.4T are:

  • IP Routing
    • Graceful OSPF Restart (RFC 3623) (Helper Mode Only)
    • Graceful Restart for OSPFv3 (RFC 5187) (Helper Mode Only)
    • OSPF Graceful Shutdown
    • OSPF Generic Time to Live (TTL) Security Check (GTSM)
    • Performance Routing (PfR) Protocol Independent Route Control (PIRO)
    • Performance Routing (PfR) EIGRP mGRE DMVPN Hub-and-Spoke Support
    • BGP Graceful Restart per Neighbor
    • Intermediate System-to-Intermediate System (IS-IS) BFD Support
    • IS-IS VRF Support
    • MPLS VPN – Inter-AS Option AB
    • BGP Route Target Changes Without PE-CE Impact
    • IS-IS MIB Support
    • MPLS VPN-BGP Local Convergence
  • IP Multicast
    • IGMP Static Group Range Support
    • IP Multicast Load Splitting – Equal Cost Multipath (ECMP) using S, G and Next-hop
    • IPv4 and IPv6 Multicast Address Group Range Support
    • Multicast MIB VRF Support
    • Multicast VPN Extranet Support
    • Multicast VPN VRF Select
    • PIM Triggered Joins
  • Call Admissions Control Enhancements for Voice and Video
    • RSVP Interface-based Receiver Proxy
    • RSVP Fast Link Repair
    • RSVP VRF lite Admission Control
  • High Availability
    • BFD client for IPv4 Static Routes
    • BFD VRF support
    • BFD Support for WAN Interfaces
  • Embedded Management
    • EEM policy description display
    • EEM policy AAA bypass
    • Multiple CLI execution in one TCL command
  • Security
    • Lightweight IPS Engines for Signatures
    • New Default IOS IPS Category signatures
    • Chaining of Traffic Scanning (Regular Expression) Tables for IPS
    • Configurable Threshold Limits for IPS Signatures
    • GET VPN VRF-Aware GDOI on GM
    • Ability to Disable Volume-based IPSec Lifetime Rekey
    • DMVPN Enhancements
  • Voice
    • Cisco Unified Border Element (CUBE) Support for SRTP-RTP Internetworking
    • CUBE Support for Out-of-dialog SIP OPTIONS Ping Messages to Monitor SIP Servers
    • UC Trusted Firewall Control Version 2
    • Cisco UC Release 8.0 SAF Support



  1. Sometimes watch is good for Cisco is not good for custumer. If you need any distance support ask them what you need to do. The biggest problem is enable license support for this version, you can use during 60 days plus 120 without a rebooting, after that you need install a license for each kind of special service. If you live in a Big country like me, where resource is not easy to find(Internet) you are in big trouble.


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