From: ccie2be (ccie2be@nyc.rr.com)
Date: Fri Sep 05 2003 - 11:00:31 GMT-3
Hi everyone,
I want to confirm my understanding of the situation where IP Phones are
connected to a 3550.
Let's say that a firm has just upgraded their switches to Cat 3550's in
preparation of a migration to IP Telephony. With the upgrade they have the
same number of ethernet ports that they had with the old switches and their
intention is to have all the PC's that were previously connected to the old
switches connect via the access port on the IP Phone which in turn will be
connected to the new Cat 3550 switches. Currently, their PC's reside in 4
different vlans, vlan 10, 20, 30 and 40 and all of these vlans exist in each
of their switches. Their plan is to have all the IP Phones in one voice vlan.
And, they need the PC's to remain in whatever vlan they're already in after
the migration.
Can this be achieved?
Based on what I understand, this can't be done. Here's the reason. Please
correct me if I'm wrong on this.
Data traffic from the PC's attached to the access port of the IP Phones is
carried in untagged frames in the native vlan. While the native vlan can be
assigned any vlan number there can be only 1 native vlan which, by default, is
vlan 1. And, the native vlan must be the same on all the Cat 3550's since
802.1q trunks area being used.
While this is my understanding from reading the 3550 config guide, this
limitation doesn't seem reasonable or smart. Would Cisco design the 3550 so
that PC's that were in different vlans would be forced to be in the same vlan
if the PC's were connected via the IP Phone?
Thanks; I greatly appreciate any help.
dt
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