You can not monitor two Vlans with one port. As a general rule you can not monitor two vlans with one sniffer the port your sniffer is connected to must be in the same vlan you are watching (no multi vlan ports allowed). It is possible to monitor both vlans at the same time with one sniffer by mirroring to one port for Vlan 10 and mirroring to a second port for Vlan 20 and then connecting a hub to these two ports and sniffing the hub. However, This is not recommended. You need to be aware that this will bridge the two Vlans and basically defeats the purpose of the Vlan.
As for the multi Vlan port. This will assign a port to more than one Vlan. So for example a server could talk to devises on both Vlan 10 and Vlan 20. The multi vlan comand will also prevent the use of a trunk on the XL series switches. As a general rule you are better off to do vlan routing to get to your server rather than to connect the server to a multi vlan port. ""Jerry Lu"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hello everyone, > > I got into a situation here: > > Hareware: Cisco Catalyst 2900XL > ISO: 12.0(5.1)XP > > Say interface FE 0/1 is assigned to Vlan 10, and interface FE 0/2 is > assigned to Vlan 20. Is it possible to make interface FE 0/3 as a SPAN > port whcih monitors both FE 0/1 and FE 0/2 ? I need to attach a sniffer > onto FE 0/3 and analyst the traffic so FE 0/3 could not be a trunk port > (the sniffer doesn't understand VLAN taggings). > > I know under normal circumstance this setup is not allowed (can't monitor > 2 vlan traffic through 1 port). But is there a work around? > > BTW, what's the meaning of the interface commands "switchport multi vlan"? > If I run this command on an interface, will this interface become a trunk > port or an access port? I can't seem to find out the detailed explanation > on this command from Cisco's website. > > Thanks for your help! Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=33575&t=33575 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
