源码:--------------------------------------------------------------------------------
r1-1(e0/0)-----(f0/1)sw(f0/2)---------r1-2(f0/0)
(f0/3)----------r1-3(e0)
cat3550 f0/2 configured with one Access vlan 20 and
one voice vlan 50
f0/1 access vlan 50
f0/3 access vlan 20
r1-2 configured with a native vlan 20 and a dot1q
trunk vlan 50 (simulating ip phone)
And ping r1-1 and r1-3 works from r1-2!
This means that cat3550 treats the voice vlan in a
very special way!
If you configure the voice vlan port as a dot1q trunk
port, you may need
to block all vlans other than the native vlan and
voice vlan. Otherwise
all other vlan packets will be sent to the ip phone...
===================================
cat3550 configuration:
interface FastEthernet0/1
switchport access vlan 50
no ip address
!
interface FastEthernet0/2
switchport access vlan 20
switchport voice vlan 50
no ip address
duplex full
speed 100
spanning-tree portfast
!
interface FastEthernet0/3
switchport access vlan 20
no ip address
!
=============
r1-1:
interface Ethernet0/0
ip address 50.1.1.10 255.255.255.0
r1-2:
interface FastEthernet0/0
no ip address
speed 100
full-duplex
!
interface FastEthernet0/0.20
encapsulation dot1Q 20 native
ip address 20.1.1.1 255.255.255.0
!
interface FastEthernet0/0.50
encapsulation dot1Q 50
ip address 50.1.1.1 255.255.255.0
!
r1-3:
interface Ethernet0
ip address 20.1.1.3 255.255.255.0
no ip directed-broadcast
!
r1-2#p 20.1.1.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 20.1.1.3, timeout is
2 seconds:
!!!!!
SUCcess rate is 100 percent (5/5), round-trip
min/avg/max = 1/2/4 ms
r1-2#p 50.1.1.10
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 50.1.1.10, timeout
is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip
min/avg/max = 1/2/4 ms
cat3550-11#sh int f0/2 swi
Name: Fa0/2
Switchport: Enabled
Administrative Mode: dynamic desirable
Operational Mode: static access
Administrative Trunking Encapsulation: negotiate
Operational Trunking Encapsulation: native
Negotiation of Trunking: On
Access Mode VLAN: 20 (VLAN0020)
Trunking Native Mode VLAN: 1 (default)
Administrative private-vlan host-association: none
Administrative private-vlan mapping: none
Operational private-vlan: none
Trunking VLANs Enabled: ALL
Pruning VLANs Enabled: 2-1001
Protected: false
Unknown unicast blocked: disabled
Unknown multicast blocked: disabled
Voice VLAN: 50 (VLAN0050)
active!!!