Monitoring a VLAN vs. an Interface

From: Andy LaPorte (andy@cloud9.net)
Date: Wed Jul 18 2007 - 00:36:58 ART


I was just going over a lab that asks to monitor a VLAN to an interface.
The goal was to monitor the received traffic.

 

The setup was 4 switches where 2-3 of the switches had ports assigned to the
VLAN that was to be monitored.

 

The solution was to setup remote spanning where the source was the
interfaces and the destination was a new VLAN for the purpose of rspan.

 

I'm a bit confused on when you would set the source as the interfaces verse
when can set the source as the VLAN.

 

Maybe an example would help with my question:

 

S1

Interface FA0/1 - VLAN 10

 

S2

Interface FA0/1 - VLAN 10

 

S4

(no ports in VLAN 10)

Interface FA0/1 - Monitor Destination

 

 

The solution was:

 

S1

VLAN 666 (this was the VTP server so it went to all switches)

 Name IDS

 Remote-span

Monitor session 1 source interface FA0/1

Monitor session 1 destination remote vlan 666

 

S2

Monitor session 1 source interface FA0/1

Monitor session 1 destination remote vlan 666

 

S4

Monitor session 1 source remote vlan 666

Monitor session 1 destination interface FA0/1

 

What I'm trying to figure out is what is the difference from the above
solution and this one:

 

S1

VLAN 666

 Name IDS

 Remote-span

Monitor session 1 source vlan 10 rx

Monitor session 1 destination remote vlan 666

 

S2

Monitor session 1 source vlan 10 rx

Monitor session 1 destination remote vlan 666

 

S4

Monitor session 1 source remote vlan 666

Monitor session 1 destination interface FA0/1

 

Now I understand when monitoring the Interface it monitors both tx and rx
but the request was only for received traffic. Any help would be great in
understanding this concept as I'm a bit confused even after going over the
doc's a few times.

 

Andy



This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:41 ART