Strange problem with RSPAN Command

Unanswered Question
Sep 20th, 2010
User Badges:


I have two access switches both are connected to my core Switches. Access Switch -1 is trunk via UTP cable and Access SW-2 is trunk via Fiber. Monitor session command is working with my Access Switch-1.  But whenever I am putting monitor session command on my access switch-2, all the connections between Access Switch-2 to my core Switch is disconnecting. When I remove monitor session command I can communicate with all direction.

My configurations are

Core Switch (3560)

monitor session 1 destination interface Fa0/11

monitor session 1 source remote vlan 556

Access Switch-1

monitor session 1 source interface Fa0/11 - 22

monitor session 1 destination remote vlan 556

Access Switch-2

monitor session 1 source interface Fa0/11 - 22

monitor session 1 destination remote vlan 556

Core Switch is my VTP Server. Others are VTP Client.  I am getting what to do. Can you guys help me.


Sultan Al Arif

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
Md. Sultan Al Arif Tue, 09/21/2010 - 20:24
User Badges:

Hi Marko

Yes I have declare 556 as Remote Span Vlan in my core Switch. My core is VTP server.How I can find where is the loop?

vragotha Tue, 09/21/2010 - 08:27
User Badges:
  • Silver, 250 points or more

Can you post a 'sh vlan' from the core and two access switches?

Marko Leopold Wed, 09/22/2010 - 04:00
User Badges:

would be great if you provide your network topology too. how are the devices connected together?

Marko Leopold Thu, 09/23/2010 - 00:12
User Badges:

hello sultan!

it looks not to complicated. from this i would say i cant see any problems. maybe the traffic that the monitored switchports produce is too high. can u look for drops and errors on the trunk ports? and do you still have the problem if you only monitor one source port?

Md. Sultan Al Arif Thu, 09/23/2010 - 01:13
User Badges:

Hello Marko

I have not check the drops and error on trunk port. But I have checked that minimum five ports can be monitored at time. When ever I add port 6 its got disconnect from other. May be you are right, its producing high data. I am monitoring Voice Data on this port as well as other data.

What I can do? Any other way that I could apply....

Marko Leopold Thu, 09/23/2010 - 01:58
User Badges:


Good to know this. I would recommend you to open up a seperate link for your RSPAN-VLAN. You can use Port-Channel if you need more throughput then. Remember that the monitoring machine need a big connection (10gb) then too. Do you need all traffic the Ports produce or can you filter something? Maybe you can use VACLs if the switches can handle this.

Md. Sultan Al Arif Thu, 09/23/2010 - 02:24
User Badges:

Hello Marko

I did not create port channel yet. I need only Voice Vlan data to motior. If I create monitor session only for Voice Vlan same problem arise.

Marko Leopold Thu, 09/23/2010 - 03:43
User Badges:

if you only need the voice vlan, why you just not try to monitor the vlan 556

at the core switch. so source is vlan 556 and destination is your monitor port.

or you just try to monitor the network port of your voice server if this is possible.

Md. Sultan Al Arif Thu, 09/23/2010 - 05:14
User Badges:


My voice Vlan is Vlan500 and Remote Vlan is 556. So at my access Switch  I need to configure Source is Vlan and Destination is Remote vlan. and My access SW Source Vlan is 556 and is monitoring port.  But this configuration is also working as same.

If I am missing some thing please describe brief.

Marko Leopold Fri, 09/24/2010 - 03:24
User Badges:

no i mean on your core switch. use vlan 500 as the source and use your

monitoring device as destination for the monitor session.


This Discussion