04-20-2007 12:03 AM - edited 03-03-2019 04:38 PM
hi,
i have the following setup:
two switches 2960 connected together over a trunked connection (802.1q)
i have two vlans configured in the switch:
vlan 1 (default) and vlan2.
i have a sniffer connected and i am mirroring the port where the two switches are connected to the sniffer.
there is a router connected on a port - this port is an access-port in vlan 2.
if i do a ping from this router over the switch-switch connection, i am not able to see the vlanid in the packet?
the pingsize is only 100 byte
i need this investigation for analysing the cos fields in the vlan-header
thank - any idea ???
04-20-2007 12:29 AM
Just to ensure you are mirroring the trunk port connection between the switch
cos bytes will be carried only on the trunk links
better would be to put 2 desktops in 2 different vlans and place them across the 2 switches and ping them... you should see the cos bytes
HTH
Narayan
04-20-2007 02:21 AM
hi,
i opened the switch-switch connection and inserted a hub - so i looked at the right frame - between the two switches.
here you can see the relevant switchkonfig:
interface FastEthernet0/1
switchport access vlan 2
switchport mode access
no logging event link-status
mls qos trust dscp
spanning-tree portfast
!
interface FastEthernet0/3
switchport access vlan 3
switchport mode access
no logging event link-status
spanning-tree portfast
!
interface FastEthernet0/24
switchport trunk allowed vlan 1-3,10,1002-1005
switchport mode trunk
!
on port 0/1 there is the enddevice connected
port 0/24 is the switch-to-switch interlink (over a hub), where i do the sniffering
the enddevice is a router, connected to port 0/1 wich the following config:
!
interface FastEthernet3/1
description to filiale
bandwidth 100000
ip address 30.30.30.1 255.255.255.0
duplex auto
speed auto
max-reserved-bandwidth 100
!
the config from other switch:
!
interface GigabitEthernet0/1
switchport access vlan 2
no logging event link-status
spanning-tree portfast
!
!
interface GigabitEthernet0/24
switchport trunk allowed vlan 1,2,10,1002-1005
switchport mode trunk
!
fakt is that i can?t see the vlan id on the interswitchlink - i do not know why !
04-20-2007 01:04 AM
Hi Raber,
As Narayan updated I believe you are sniffing the trunk interface?
Also can you post teh output of
"sh run | in monitor"
Regards,
Ankur
04-20-2007 02:22 AM
hi,
i opened the switch-switch connection and inserted a hub - so i looked at the right frame - between the two switches.
here you can see the relevant switchkonfig:
interface FastEthernet0/1
switchport access vlan 2
switchport mode access
no logging event link-status
mls qos trust dscp
spanning-tree portfast
!
interface FastEthernet0/3
switchport access vlan 3
switchport mode access
no logging event link-status
spanning-tree portfast
!
interface FastEthernet0/24
switchport trunk allowed vlan 1-3,10,1002-1005
switchport mode trunk
!
on port 0/1 there is the enddevice connected
port 0/24 is the switch-to-switch interlink (over a hub), where i do the sniffering
the enddevice is a router, connected to port 0/1 wich the following config:
!
interface FastEthernet3/1
description to filiale
bandwidth 100000
ip address 30.30.30.1 255.255.255.0
duplex auto
speed auto
max-reserved-bandwidth 100
!
the config from other switch:
!
interface GigabitEthernet0/1
switchport access vlan 2
no logging event link-status
spanning-tree portfast
!
!
interface GigabitEthernet0/24
switchport trunk allowed vlan 1,2,10,1002-1005
switchport mode trunk
!
fakt is that i can?t see the vlan id on the interswitchlink - i do not know why !
04-22-2007 05:54 AM
friend,
May be these 2 links can answer the behavior you are seeing
http://wiki.ethereal.com/CaptureSetup/VLAN#head-81781716144f2855ab0aff2f8b752e95f2562efb
http://www.ethereal.com/faq#q7.11
HTH, rate if it does
Narayan
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