ERSPAN to record Voice traffic

Unanswered Question
Nov 13th, 2007

Hello .

We are working on deploying some NICE voice recorder on our infrastrucure to record our IP telephony traffic .

We actually use a fully routed network to go from one building to another .(3 buildings)

Inside each building we r deploying a fully Layer 3 routed netwrok model .

This means that Vlans are not trunked from Access to distribution but we use routed interface to connect them instead .

I know RSPAN is working well in this situation and i have pretty much an idea about how to deploy it on the network to record each individual phone calls . We will then RSPAN the traffic from each voice Vlans on each access switches to a pair a voice recorder (For resilience) inside each building.

My idea was to use ERSPAN instead of RSPAN . The major difference between the two is ERPSAN allow you to "span" your traffic through a layer 3 domain .(RSPAN is limited to a layer 2 domain).

By using ERPSAN we will then ERSPAN the traffic from only one voice recorder instead of two in each building . Each voice recorders backuping each other.

I am struggling to have a feedback or any experience on that and i am not sure someone has ever done it before .

Anything unclear please ask.

Thanks for your replies , i look forward to hear everyone imnputs here.


I have this problem too.
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hassan_oudeh Sun, 12/16/2007 - 12:00


actually i have the exact same scenario but instead of 3 buildings i have only 1 tower with 24 floors and 3750 on each floor with L3 routed eigrp network with the 6506,

actually my problem is ERSPAN as i read from the datasheets is not supported on the 3750 switches and only supported on the 6500 ?!

my recording server is connected to the 6500

so i dont know if you find something or still waiting :)

please if you have an idea let me know



sg_london Tue, 12/18/2007 - 09:00

Hello Hassan.

Unfortunately ERPSAN is only enable on high end lpatform (6500 / Sup720 / sup32) .

We have a Proof of concept plan with Cisco mid january to validate the feature for voice recording purpose . Have you found anything on your side ?



hassan_oudeh Thu, 02/21/2008 - 09:06

Hi David,

actually there is no solution for such a setup like this, what i did is connect another L2 trunk and trunked RSPAN to the recorder !

i know it is not the best practice to have both L3 and L2 in the same edge switch but unfortuntly there is no other way to do it !!

i think cisco should come with a solution for such a common issue !




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