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Understanding the Cisco IOS File Name Convention

Cisco IOS naming conventions can seem a bit confusing, however to avoid bricking a device its important that you have a full understanding of the Cisco IOS naming conventions.

Before planning an upgrade or install of an IOS file, it is very important that you check the name of each IOS file.

The IOS file name is usually similar to this form

1. The xxxx is the platform. For example:

c1005 – For 1005 platform

c1600 – For 1600 platform

c1700 – For 1700, 1720, and 1750 platforms

c2500 – For 25xx, 3xxx, 5100, and AO (11.2 and later only) platforms

c2600 – For 2600 platform

c2800 – For Catalyst 2800 platform

c2900 – For 2910 and 2950 platforms

c3620 – For 3620 platform

c3640 – For 3640 platform

c4000 – For 4000 platform (11.2 and later only)

c4500 – For 4500 and 4700 platforms


2. The yyy is the feature set. For example,

b For Apple talk support

boot For boot image

c For CommServer lite (CiscoPro)

drag For IOS based diagnostic image

g For ISDN subset (SNMP, IP, Bridging, ISDN, PPP, IPX, and AppleTalk)

i For IP sebset (SNMP, IP, Bridging, WAN, Remote Node, and Terminal Services)

n For IPX support

q For asynchronous support

t For Telco return (12.0)

y For reduced IP (SNMP, IP RIP/IGRP/EIGRP, Bridging, ISDN, and PPP) (c1003 or c1004)

z For managed modems

40 For 40 bit encryption

50 For 50 bit encryption


3. The ww is for the format (where the IOS file runs in the router)

f For flash

m For RAM

r For ROM

l For the image will be relocated at run time

The file might also be compressed. The following letters denote the compression type,

z For zip compression

x For mzip compression

w For “STAC” compression


aaa-bb represent the version of the IOS. It is usually read like this “Version aa.a(bb)”. The last part of the IOS file name might contain letters like T (new feature release identifier), S (individual release number), or XR (modular packages).