Walter Roberson
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 Posted:
Mon Jun 13, 2005 4:20 pm Post subject:
Re: 802.1q vlans trunking |
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In article <1118653774.646688.119840@g43g2000cwa.googlegroups.com>,
julde <jdelapierre@neuf.fr> wrote:
:I have to pass packets between 2 switches with vlans. One of these
:switches permit to create 256 vlans maximum. I had to configure one
:port of this switch in trunk mode in order the two switches could
:communicate. I think I had to add the vlans I want to the trunk port.
:But can the trunk port transport more than 256 vlans (because of the
:limit of 256 vlans of one of the switch)?
The answer will vary with the switch model and software release.
A switch that only allows 256 vlans to be created might have only
256 slots in its per-VLAN MAC address tables, or might only use an
8-bit number internally in storing the information about which MAC is
on which VLAN.
Sometimes, though, it is just a user interface limitation.
I suspect it would be more likely to work if you are in
single spanning-tree mode than in per-VLAN spanning-tree mode.
The "magic numbers" of VLANs that I have heard of in the past include
240, 256, 1000, 1018, 1024, 2000, 4000, and 4096.
It is not uncommon for Cisco switches to support 1024 in "VTP mode"
(which allows dynamic reconfiguration of VLANs from a master machine),
and 4096 in "VTP Transparent mode" -- i.e., the limits can depend on
exactly how the switch is being used.
--
History is a pile of debris -- Laurie Anderson |
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