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Cisco VLAN IOS comfig help ...

Cisco VLAN IOS comfig help ...# Internet - 有缘千里一线牵

L*t2004-11-22 08:11

1 楼

What's the effect of the commands below?
interface FastEthernet0/2
switchport access vlan 2
Does it means this FE port expects incoming frames carrying VlanID 2 ? Or it
means all incoming frames (either with or without vlanID2, and discard any
with other VlanIDs) will be tagged with VID 2? Similarly in egress direction.
Thanks in advance!

s*a2004-11-22 08:11

2 楼

port fa0/2 will be in vlan 2
all the packets to and from the port will be tagged with VLAN ID 2

【在 L******t 的大作中提到】

: What's the effect of the commands below?
: interface FastEthernet0/2
: switchport access vlan 2
: Does it means this FE port expects incoming frames carrying VlanID 2 ? Or it
: means all incoming frames (either with or without vlanID2, and discard any
: with other VlanIDs) will be tagged with VID 2? Similarly in egress direction.
: Thanks in advance!

L*t2004-11-22 08:11

3 楼

Thank you, simba.
What confuses me is, at the lowest level of a cascaded switches, there should
be some ports where incoming frames are tagless, but each of these ports is
configured to one (its default) vlan. I guess all incoming frames will be
tagged with the port's default vid before further processing. I am wondering
if the config commands I mentioned are used to config such ports? On the
reverse direction, the port should remove any vlan tags before transmitting
egressing frames, since user

【在 s***a 的大作中提到】

: port fa0/2 will be in vlan 2
: all the packets to and from the port will be tagged with VLAN ID 2

s*a2004-11-22 08:11

4 楼

sorry. actually there is sth wrong with what i said.
you are right.
the cisco access switch will remove the tag before it sends the packet
to the host that connects to the port
add the tag after it gets packets from the host
if you sniff the traffic of NIC of your PC,
layer 2 header will be just
Dest Mac, Source Mac, Type(IP)
if you sniff the traffic of the switch port,
there is extra bytes for VLAN header between eth and IP
ethereal.com will be a good tool when you want to
figure out the detai

【在 L******t 的大作中提到】

: Thank you, simba.
: What confuses me is, at the lowest level of a cascaded switches, there should
: be some ports where incoming frames are tagless, but each of these ports is
: configured to one (its default) vlan. I guess all incoming frames will be
: tagged with the port's default vid before further processing. I am wondering
: if the config commands I mentioned are used to config such ports? On the
: reverse direction, the port should remove any vlan tags before transmitting
: egressing frames, since user

b*e2004-11-22 08:11

5 楼

Actually, this is not true ...
VLAN tags are only imposed/stripped on a trunk port, packets come in/going out
a access port is not tagged (one exception is that you configure a access port
to be .1q tunnel in which case incoming packets are tagged).

should
is
wondering
transmitting
vlan

【在 s***a 的大作中提到】

: sorry. actually there is sth wrong with what i said.
: you are right.
: the cisco access switch will remove the tag before it sends the packet
: to the host that connects to the port
: add the tag after it gets packets from the host
: if you sniff the traffic of NIC of your PC,
: layer 2 header will be just
: Dest Mac, Source Mac, Type(IP)
: if you sniff the traffic of the switch port,
: there is extra bytes for VLAN header between eth and IP