RSPAN causing instability

[Frank den Haan]

We are trying to configure RSPAN at one of our sites in order to record voice calls using CallRex. We have it working successfully at another site using RSPAN (smaller site with 4x 3560 PoE switches), but when trying to set it up at this site, it causes "instability" for the voice network to say the least (some phones display one-way audio, UCM down message on the phone...not good). The calls are actually recording successfully on the CallRex server, but we cannot leave the RSPAN config in place due to the issues it causes. As soon as the RSPAN commands are removed, everything behaves normally. Here is the relevent config:

EDGE Switch 1 (Cisco 2960-48LPS):

vlan 210

name CALL-RECORDING

remote-span

interface GigabitEthernet1/0/1

description Trunk to Core Switch

switchport trunk native vlan 999

switchport trunk allowed vlan 100,200,210

switchport mode trunk

monitor session 1 source interface Gi1/0/47   (IP phone plugged in here)

monitor session 1 filter vlan 200   (voice VLAN)

monitor session 1 destination remote vlan 210   (remote-span VLAN)

Core Switch 1 (Cisco 4510):

spanning-tree vlan 210 priority 24576   (along with all the other VLANs with are root on this switch)

vlan 210

name CALL-RECORDING

remote-span

interface GigabitEthernet4/1

description Trunk to Edge Switch

switchport trunk encapsulation dot1q

switchport trunk native vlan 999

switchport trunk allowed vlan 100,200,210

switchport mode trunk

spanning-tree guard root

monitor session 1 source remote vlan 210   (remote-span VLAN)

monitor session 1 destination interface Gi4/6   (sniffer port on CallRex server)

The config is pretty stright-forward, but as mentioned above, is causing major problems when turned up.

CPU / memory levels are normal. Nothing shows up in the sh log on either the Edge or Core switches.

Does anyone have any ideas what the problem could be? Many thanks in advance!

[Gabriel Hill]

Hello Frank,

Could you verify that spanning-tree is acting normal when this configuration is active?

Show spanning tree vlan 210

Also, when it is active, do a: show interface trunk  --> Be sure that VTP isn't pruning the vlan for some strange reason.

Thanks,
Gabriel

[paul driver]

Hello
Can you try specifying the port which this span traffic should traverse - see if this make a difference

monitor session 1 source interface Gi1/0/47 (IP phone plugged in here)
monitor session 1 filter vlan 200
monitor session 1 destination remote vlan 210 reflector-port xxxx


Res
Paul

Sent from Cisco Technical Support iPad App

[Frank den Haan]

Thanks for the reply Paul. I tried to specify the reflector-port, however the 4510 and 2960S switches do not seem to support that command.

As a workaround, we ended up just monitoring the whole voice VLAN on the 4510 and spanning it to the sniffer port (also on the 4510). The majority of the calls are being successfully recorded.

[Frank den Haan]

Thanks for the reply and suggestion Gabriel. As far as I could tell, spanning-tree seemed fine. I also had TAC on the phone the other day and we checked spanning-tree while the issue was occurring. Nothing seemed out of the ordinary.