From: David Siwula (DSiwula@xxxxxxxxx)
Date: Tue Aug 28 2001 - 14:07:58 GMT-3
Great reply......very informative!!
-----Original Message-----
From: Bowen, Shawn [mailto:sbowen@neteffectcorp.com]
Sent: Tuesday, August 28, 2001 9:09 AM
To: 'ccielab@groupstudy.com'
Subject: RE: Weird Vlan problem !! (+ ip phone)
Joy, oh joy... I get to play with IP Phones and Voice stuff way more
than I
want too. Here is the skinny (I crack myself up).
The 6509 probably has a configuration for each of it's ports somewhat
like
this:
interface FastEthernet0/10
switchport trunk encapsulation dot1q
switchport trunk native vlan 1
switchport mode trunk
switchport voice vlan 50
In this example (this is a one port snapshot, all the ports are the
same) we
use a newer feature of the IOS that allows definition of a VVLAN(Voice)
and
DVLAN(Data). When an IP phone is plugged into the port it gets VVLAN IP
address, yet when a CPU is plugged in it gets a DVLAN. What's even
cooler
is that when a phone such as a 7960 is plugged in that has a built in 3
port
switch (2 physical and one virtual ports) it will join BOTH VLAN's. The
phone will use the VVLAN and the CPU plugged into the back of the phone
will
use the DVLAN.
Now, as far as who assigns the IP address it is a DHCP server for both
PC's
and IP Phones, the difference is the Switch Port configuration. The PC
appears to come from the DVLAN and the Phone appears to come from the
VVLAN.
It does not matter where the DHCP server is placed if it is configured
properly (supernets for NT). If you notice in the config above I am
using
802.1q for VLAN trunking. That is because the phones use it natively
and
tag to VoIP data as COS 5 and the PC data as COS 1, this QOS is kind of
enabled by default. To be effective you must match the switch's trunk
mode
with the phones, use 802.1q for all trunk ports. The phones do use TFTP
server, but for the main configuration. Items such as the BIN image and
other such items are on the TFTP server.
Another cool note about the IP phones is that they use another new IOS
feature, two way CDP, yup it's true. Some switches come in powered
model's
now, they provide 48 volts DC to pins 7&8. This is used by IP phones
and
Cisco Aironet 350's now, more to come. The problem is that the switch
needs
to know hoe many watts (if any!) to send a given port, thus the modified
CDP. When an IP phone is plugged in it sends this new CDP packet and
tells
the switch it is an IP phone, the switch gives a low voltage for the
phone
to begin functioning and asks the phone how much juice to send, via CDP.
If
a PC is plugged into the switch there is no request for juice, and if a
phone WAS plugged in and then a PC is plugged in around 10 seconds later
there is no more juice. Makes you think twice about fast fingering a
bunch
of ports in a wiring closet now doesn't it!
Ok, there is intro to IP phones 100.1,
Shawn
-----Original Message-----
From: Jeongwoo Park [mailto:jpark@wams.com]
Sent: Tuesday, August 28, 2001 2:49 AM
To: 'ccielab@groupstudy.com'
Subject: Weird Vlan problem !! (+ ip phone)
Hi all
Here is my issue.
Cisco 6509 switch has two vlans(vlan 1 and vlan 10)
Now, all the LAN users are hanging off the vlan 1 getting DHCP ip
address
from the DHCP server that also belongs to vlan 1.
All the Cisco ip phones are hanging off the vlan 10, and the separate
DHCP
server that assigns dynamic ip addresses to the ip phones also is hang
off
the vlan 10.
Now my issue is that when I take my laptop pc and hook it up to vlan 10
where all ip phones are, I get ip address from the DHCP server at vlan
1.
It is so weird.
Is it just weird thing or I am missing something?
Have any of you guys encountered this problem before?
Thanks
JP
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