On Wed, Sep 20, 2000 at 01:11:30PM +0200, Oleg Kostine wrote:
> One little detail: If you use 802.1q on Cisco you have only one STP domain
> for all vlans over the trunk. 29xx,35xx or 6x00 manuals is a good source
> for more info.
According to:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_5/sw_cfg/spantree.htm
"Spanning Tree and IEEE 802.1Q Trunks
IEEE 802.1Q VLAN trunks impose some limitations on the spanning-tree strategy
for a network. In a network of Cisco switches connected through 802.1Q
trunks, the switches maintain one instance of spanning tree for each VLAN
allowed on the trunks. However, non-Cisco 802.1Q switches maintain only one
instance of spanning tree for all VLANs allowed on the trunks.
When you connect a Cisco switch to a non-Cisco device through an 802.1Q
trunk, the Cisco switch combines the spanning-tree instance of the 802.1Q
native VLAN of the trunk with the spanning-tree instance of the non-Cisco
802.1Q switch. However, all per-VLAN spanning tree information is maintained
by Cisco switches separated by a cloud of non-Cisco 802.1Q switches. The
non-Cisco 802.1Q cloud separating the Cisco switches is treated as a single
trunk link between the switches."
Yes, in cat6k docs it does say though, that 802.1q will run only one STP.
This makes me believe, that 6k is not a Cisco Switch (tm). :)
[not 100% relevant info on]
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/sw_5_5/cnfg_gd/vlans.htm :
"Mapping 802.1Q VLANs to ISL VLANs
The valid range of user-configured Inter-Switch Link (ISL) VLANs is 1-1000.
The valid range of VLANs specified in the IEEE 802.1Q standard is 0-4095. In
a network environment with non-Cisco devices connected to Cisco switches
through 802.1Q trunks, you must map 802.1Q VLAN numbers greater than 1000 to
ISL VLAN numbers.
802.1Q VLANs in the range 1-1000 are automatically mapped to the
corresponding ISL VLAN. 802.1Q VLAN numbers greater than 1000 must be mapped
to an ISL VLAN in order to be recognized and forwarded by Cisco switches."
[not 100% relevant info off]
[skip]
P.S. Please tell me, how is this whole 802.1q/STP story bad for you? I don't
get it, why I should care. Mind it, but not *care*. ;^)
SY,
-- CCNP,CCDP (R&S) Dmitri E. Kalintsev CDPlayer@irc Chief of Network Operations @ Sonorous Networks dek @ hades.uz phone: +27 11-327-1524 fax: 327-7648 http://hades.uz UIN:7150410 cell +27 82-336-1033
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