"With Cisco IOS Software Release 12.1(13)E and later, VLAN IDs might be in the range of 1 to 4094, except in the case of reserved VLANs. With Cisco IOS Release 12.1(11b)E or later, you can remove VLAN 1 from a trunk port. Even after removing VLAN 1 from a trunk, the trunk interface continues to send and receive management traffic. For example, CDP, VTP, Port Aggregation Protocol (PAgP), and DTP all use VLAN 1, regardless of the existence of VLAN 1 on the port."
How can we tell if certain ios is later release than ios 12.1(13) E? For example if we have windows OS like windows 95. windows 98. windows 2000 etc we can tell which windows OS is most latest.
Please look at the number inside the "brackets". The higher the number the later.
If you have access to Cisco Software Downloads, it keeps "tracks" of what you are downloading. It will also "inform" you that you've LAST downloaded, for instance, an IOS for the 2960S version 15.0(1)SE and the latest one available is 15.0(1)SE2. Both versions are HTML links so if you click on the newer version the page will take you to the download page.
If you do a "sh ver" on the switch or router, it will tell you what version of IOS you are running. I can tell you that 12.1(13)E is pretty old. After 12.1 revisions came 12.2, 12.3 and 12.4. Now days for routers the latest is IOS 15 with multiple revisions.
Also if you access the downloads section on the cisco website and look for an IOS you will be able to see the IOS's list in order of their evolution.
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