From: Bownds, Clayton (Clayton.Bownds@xxxxxxxxxxxxx)
Date: Thu Mar 01 2001 - 20:32:54 GMT-3
PVST should still be supported on dot1q trunks as long as both ends of trunk
are Cisco devices, so there isn't really a ISL STP performance advantage
there... the newer Catalyst code supports up to 4K VLANs, so there isn't a
dot1q advantage there any longer... I would recommend ISL only because it
has proven to be more stable in my experience, but that is personal
preference. The 2948G (NOT the G-L3) runs Cat4K code and is, in many ways,
functionally equivalent to the 4K series Catalysts. The 4000's do not
support ISL on all native switchports. ISL is only supported on the gig
uplinks on the Layer-3 module. Since the 2948G is fixed config, that isn't
an option... so no, ISL isn't supported.
So, "the bottom line is", when deal with ALL Cisco gear, there isn't a
performance advantage from one to the other... there is however a
configuration difference in that 802.1q does not tag the native VLAN of the
trunk so that must be taken into consideration when configuring
switch-switch and switch-router trunk links. You can find out more about
this here:
CatOS to XL trunks: http://www.cisco.com/warp/public/473/43.html
CatOS to CatOS dot1q: http://www.cisco.com/warp/public/473/27.html
General trunking:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat5000/rel_5_2/config/e
_trunk.htm
CatOS ISL trunking:
http://go3.163.com/~lihaijun/ciscollz/Cisco%20-%20Configuring%20ISL%20VLAN-T
runking%20on%20the%20Catalyst%205000%20Switches.htm
oh, one more thing... you can bridge between ISL vlan sub-ifs in most IOS
revisions, but dot1q bridging isn't supported until 12.13T
Thanks,
Clayton
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Blade Of Darkness
Sent: Thursday, March 01, 2001 8:20 AM
To: ccielab@groupstudy.com
Subject: ISL Trunking vs dot1q
Group,
Has anyone experience the pros and cons of isl vs dot1q? I am asking about
performance-wise and all equipments are ciscos. Why would one chose to use
isl instead of dot1q? And can the cisco WS2948G (only G)
use isl? I only see dot1q supported.
Thanks.
Blades of Darkness.
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