RSPAN issues

Unanswered Question
Jan 3rd, 2008

Hi,

i'm trying to establish a rspan session with a network that consist of 2950 for access switch and 2 3550 for core switch that handle all inter-vlan routing.

My source and destination are 2950 switches.

This is the result for the source switch:

Session 1

---------

Type : Remote Source Session

Source Ports :

Both : Fa0/19

Reflector Port : Fa0/21

Dest RSPAN VLAN : 550

This is the result for the destination switch:

Session 1

---------

Type : Remote Destination Session

Source RSPAN VLAN : 550

Destination Ports : Fa0/24

Encapsulation : Native

Ingress: Disabled

This is the result on all switches:

Remote SPAN VLANs

----------------------------

550

This is according to the instruction found on this URL:

http://www.cisco.com/en/US/docs/switches/lan/catalyst2950/software/release/12.1_19_ea1/configuration/guide/swspan.html

The only thing that i pick up with the probe is broadcast information but no data from the source computer. When i configure a local SPAN, my probe picks up all information.

has anybody ever been able to configure a RSPAN on 2950 ??

thanks

I have this problem too.
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mchin345 Wed, 01/09/2008 - 12:46

Verify the following

1.The Cisco Catalyst 2950 switches can only have one SPAN session active at a time. The Cisco Catalyst 2950 switches can monitor only source ports, not VLANs.

2.If a 10-Gigabit Ethernet module port is configured as a SPAN or RSPAN destination port, its link rate decreases.

3.SPAN destinations never participate in any spanning tree instance. SPAN includes BPDUs in the monitored traffic, so any bridge protocol data units (BPDUs) seen on the SPAN destination are from the SPAN source.

tonyp8581 Wed, 01/09/2008 - 13:28

Hi,

thx for your reply,

1. a) I do have only one active session running. b) My intention is too monitor an acces port not a VLAN.

2. My RSPAN destination is a FastEthernet port and it's also configured as an acces port.

3. I do see some BPDU in the packet capture.

That explains it.

Since last week, i did some more reading on RSPAN.

It's said that a intermediate switch cannot be a 2950 or you cannot do RSPAN with 2950.

I am using 2950. Can you confirm that?

thx again

Hi,

Do you have trunks between the switches? If so then make sure that you allow vlan 550 to pass on the trunks so that the RSPAN VLAN can cross all switches. I know that was my problem a while back.

The monitor sessions themselves look okay. Does the destination port have `switchport access vlan 550` in its config?

thanks,

Bryan

tonyp8581 Thu, 01/10/2008 - 06:57

Hi Brian,

Trunks are configured between switches to cross all vlan packets.

The vlan 550 was created for RSPAN use only.

your quote:

"If so then make sure that you allow vlan 550 to pass on the trunks so that the RSPAN VLAN can cross all switches"

I'm using command to verify this:

show vlan remote-span. Is that what your talking about ?

I have tried to place my destination port in vlan 550 but to no avail.

In my capture file, i only see broadcast information.

My understand, you have been able to create a RSPAN session on a network consisting of 2950. is that correct ?

thx

Tony

Kevin Dorrell Thu, 01/10/2008 - 07:22

If you are seeing only the broadcasts, then it sounds as if the VLAN is learning. An RSPAN VLAN must be configured as such (on the VTP domain if you are client-server, or on all switches individually if you are in transparent mode). That disables learning on that VLAN.

Please check that VLAN 550 is correctly set up as a RSPAN VLAN. You should see it in show vlan in the "Remote SPAN VLANs" on every switch.

Kevin Dorrell

Luxembourg

tonyp8581 Thu, 01/10/2008 - 07:54

Kevin,

My VTP server is running on a 3550 and all my 2950 are running as clients.

Here's the result of my command and all switches have the same information.

S2950#sh vlan remote-span

Remote SPAN VLANs

--------------------------------

550

A point you brought up, how do i verify if the RSPAN VLAN is still in learning mode.

thx

Kevin Dorrell Thu, 01/10/2008 - 08:10

It looks OK. If it's marked as an RSPAN VLAN, then it will not be learning - that is basically what an RSPAN VLAN is.

Out of ideas for the moment.

Kevin Dorrell

Luxembourg

Kevin Dorrell Fri, 01/11/2008 - 01:44

Tony,

Thanks for getting back to tell us how you resolved it. That way we can all benefit from your experience.

Kevin Dorrell

Luxembourg

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