Cisco LAN Switching by Clark and Hamilton Cisco Press ISBN 1-57870-094-9
For VLAN 1, BPDUs are sent to the usual Spanning Tree multicast address of
01-80-C2-00-00-00. All switches recognize this address.
For all other VLANs, BPDUs are sent to the multicast address of
01-00-0C-CC-CC-CD. Non Cisco switches do not recognize them and flood them.
They are "tunneled" through regular 802.1Q switches. Cisco switches
recognize them as BPDUs and use them for PVST+.
> -----Original Message-----
> From: Fred Danson [mailto:[EMAIL PROTECTED]]
> Sent: Thursday, February 01, 2001 12:57 PM
> To: [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]
> Subject: RE: ISL vs. 802.1Q
>
>
> If Cisco were to add-on to dot1q, how would it be able to
> communicate with
> other non-Cisco routers using 802.1q?
>
>
> >From: Chris Supino <[EMAIL PROTECTED]>
> >Reply-To: Chris Supino <[EMAIL PROTECTED]>
> >To: Jun Pati <[EMAIL PROTECTED]>, [EMAIL PROTECTED]
> >Subject: RE: ISL vs. 802.1Q
> >Date: Wed, 31 Jan 2001 21:04:30 -0500
> >
> >Jun,
> >
> >Used to be that ISL supported a spanning-tree per VLAN, where Dot1q
> >supported only a single spanning-tree. I was told at a
> seminar recently
> >that
> >Cisco has expanded the capabilities of their implementation
> of Dot1q, and
> >it
> >is now almost as fully featured as ISL, including supporting a
> >spanning-tree
> >per vlan. ISL is being phased out.
> >
> >Christopher Supino
> >MCSE, MCP+I, CCNA, CNA Netware 5, Compaq ASE
> >Senior Systems Engineer
> >TransNet Corp.
> >
> >-----Original Message-----
> >From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
> Behalf Of
> >Jun Pati
> >Sent: Wednesday, January 31, 2001 7:29 PM
> >To: [EMAIL PROTECTED]
> >Subject: ISL vs. 802.1Q
> >
> >
> >What is the advantage of using ISL on an all-Cisco network
> compared to
> >dot1Q
> >aside from being able to handle frames larger than the ethernet mtu.
> >
> >
> >_________________________________
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