I'm studyng for CCNA exam, and I am a little confused about encapsulation dot1Q command. When do I need to use that command? Does it required for configuring every trunk port on switch or what?
Thanks!
I'm studyng for CCNA exam, and I am a little confused about encapsulation dot1Q command. When do I need to use that command? Does it required for configuring every trunk port on switch or what?
Thanks!
All trunks must use either dot1q or isl encapsulation. You use that command, or the equivalent ISL command to set the encapsulation type, and yes it must be on each port that you are trunking on the switch. Additionally, the switch on the other side of the trunk must be configured the same way.
Mark,
It depends on the switch model. Some switches by default have ports (interfaces) in the "access mode" and will never become trunks. Some switches (especially with newer software) have all ports in "auto mode", so, if they sense the active attempt to become trunk - they will become a trunk. Some switches support two encapsulation methods - ISL and 802.1q, so, you have to specify which trunking protocol to use (older switches have ISL by default). Newer switches do not support the Cisco's proprietary ISL protocol, so, the only option for them is DOT1Q, so, you do not have to specify it.
Good luck,
Mike CCNP, CCDP, CCSP, CCVP, MCSE W2K, MCSE+I, Security+, etc. CCIE Voice (in progress), CCIE R&S (next)
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Thanks for answers, now it is clear. The types of switch are 3550/3560 and
2950T. Thanks again!Mark,
I don't keep it in my head, which switch has it and which is not, but if you type "swi ?" in the interface configuration mode, you will see if the command "swi encap" available at the switch. Also you can check interface capabilities (sh int cap) - it will show you supported trunking modes (along with a bunch of other valuable information).
Good luck,
Mike CCNP, CCDP, CCSP, CCVP, MCSE W2K, MCSE+I, Security+, etc. CCIE Voice (in progress), CCIE R&S (next)
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The 2950 is dot1q only, the 3550 supports isl and dot1q. I don't know about the 3560.
>
The 3560 can do ISL and .1q trunking both. The 2950/2960 are .1q only as you state.
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