From: Cameron, John (johcamer@cisco.com)
Date: Tue Feb 18 2003 - 20:09:43 GMT-3
From the 3550 config guide:
"switchport trunk encapsulation negotiate"
Specifies that the interface negotiate with the neighboring interface to
become an ISL (preferred) or 802.1Q trunk, depending on the configuration
and capabilities of the neighboring interface.
The trunking mode, the trunk encapsulation type, and the hardware
capabilities of the two connected interfaces determine whether a link
becomes an ISL or 802.1Q trunk.
also:
By default, an interface is in Layer 2 mode. The default mode for Layer 2
interfaces is switchport mode dynamic desirable. If the neighboring
interface supports trunking and is configured to allow trunking, the link is
a Layer 2 trunk or, if the interface is in Layer 3 mode, it becomes a Layer
2 trunk when you enter the switchport interface configuration command. By
default, trunks negotiate encapsulation. If the neighboring interface
supports ISL and 802.1Q encapsulation and both interfaces are set to
negotiate the encapsulation type, the trunk uses ISL encapsulation.
HTH,
JDC
-----Original Message-----
From: Jerry [mailto:phase90@comcast.net]
Sent: Tuesday, February 18, 2003 3:18 PM
To: FRANCISCO JAVIER COPETE AGUADO; Group Study CCIE LAB
Subject: Re: Default trunk encapsulation
I vote ISL because #1) Cisco proprietary for Cisco to Cisco trunk
and #2) it can form trunk with lower-end Cisco switches that don't
understand dot1q
Jerry
----- Original Message -----
From: FRANCISCO JAVIER COPETE AGUADO <F.COPETE.AGUADO@valenciamail.net>
To: Group Study CCIE LAB <ccielab@groupstudy.com>
Sent: Tuesday, February 18, 2003 12:14 PM
Subject: Default trunk encapsulation
> Hi group,
>
> if you have two Cat 3550 connect with a crossover cable, ports in mode
> desirable and encapsulation negotiate. What's the default
> encapsulation? ISL or 802.1Q?
>
> If the default encapsulation is ISL, is possible to force encapsulation
> 802.1Q without enable 802.1Q?
>
> Thank you in advance.
>
> Regards.
>
>
> Copete
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