HowTo test SRST switchover

Unanswered Question
Nov 19th, 2007

How do I switch a ATA186 to SRST mode without disturbing other network services and devices?

I have to check SRST functionality (switchover & fallback) and I only have access to Callmanager 4.2.3, the Voice Gateway (H.323) and the ATA186 itself. The voice gateway isn't the default gateway and apart from SCCP signalling so I can't apply an ACL there. The other networking devices btw. CCM and ATA are not under my controll.

My first idea was to configute a static host route to ATA's IP on CCM.

But isn't there a less critical way to put an ATA into SRST. And how to put it back to CCM controlled mode?

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
ccieid10t Mon, 11/19/2007 - 06:39

In order for SRST to kick in, it has to lose connectivity to CCM. You can put in a static route to a null interface.


Ip route (CCM IP) int null 0

jason-calbert_2 Mon, 11/19/2007 - 06:39


I'm not positive if this will work with an ATA but this is what I do to test a phone with SRST. If the phone and the SRST router are in the same VLAN/subnet I change the default gateway of the phone it's self so that it can't reach callmanager but can reach the SRST router because they are in the same VLAN/Subnet. In theory you should be able to do this with ATA's.



pwellmann Tue, 11/20/2007 - 03:15

Hi all,

I have tested a static route on all CCM Servers yesterday evening and it works well.

On CCM 4.x with W2000 you can simply route CCM traffic to ATA's Device-IP to an unused IP-Address within the same subnet:

route add mask

SRST will kick in after 30 sec. After deleting the static route:

route delete mask

ATA will fallback from SRST after 120 sec.

There was no impact to other devices. Don't forget to configure the static route on all CCM Servers and to disable ATA's the 2nd unused analog port. Without disabling the 2nd port, ATA won't fallback from SRST to CCM-controlled.

Kind regards


pwellmann Thu, 06/05/2008 - 23:14

CCM 4.x accept static routes but CUCM 5.x and 6.x do not (see SR CSCse56091)

So you have to configure the device with a wrong default gatewa address. But be aware, you might rech the device never again ;-)

A better solution is to setup a VLAN Filter on an attached Catalyst 3560 switch:


mac access-list extended gtwy

permit host 0090.0b08.0507 host 0019.2F74.BCA3

permit host 0019.2F74.BCA3 host 0090.0b08.0507


vlan access-map block-gtwy 10

action drop

match mac address gtwy

vlan access-map block-gtwy 20

action forward

vlan filter block-gtwy vlan-list 10




This Discussion