[cisco-voip] WAN failure in call manager

Sun Dec 13 16:07:46 EST 2009

That is very very neat indeed. I might even lab that up later.

On Sat, Dec 12, 2009 at 12:39 AM, Wes Sisk <wsisk at cisco.com> wrote:

>  yep!  there are some interesting scenarios that arise where phones may
> failover rather aggressively (geometric tcp). in recent cm versions this is
> configurable on the phone configuration page.  there are also scenarios
> where router may artificially failover (dsp issues cause ios to stop
> responding to crcx/dlcx/etc.)
>
> I like your idea lelio.  allows you to transition all devices at a remote
> site as mostly a single entity.  However, it depends on choosing the
> appropriate trigger event.  The trigger even may differ depending on network
> topology and implementation
>
> /wes
>
>
> On Friday, December 11, 2009 9:21:28 AM, Lelio Fulgenzi
> <lelio at uoguelph.ca> <lelio at uoguelph.ca> wrote:
>
> neat suggestion. i just read up on eem. pretty powerful stuff.
>
> on the corollary, you could also monitor when a phone registered before
> your MGCP gateways and then force the MGCP gateways to register as well
> using similar ACLs.
>
> i likes it!
>
>
> ---
> Lelio Fulgenzi, B.A.
> Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
> (519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> "Bad grammar makes me [sic]" - Tshirt
>
>
> ----- Original Message -----
> From: "Wes Sisk" <wsisk at cisco.com> <wsisk at cisco.com>
> To: "Lelio Fulgenzi" <lelio at uoguelph.ca> <lelio at uoguelph.ca>
> Cc: cisco-voip at puck.nether.net, "anand" <anand.eee at gmail.com><anand.eee at gmail.com>,
> "Karen Cheng" <kaz.cheng at gmail.com> <kaz.cheng at gmail.com>
> Sent: Friday, December 11, 2009 9:13:12 AM GMT -05:00 US/Canada Eastern
> Subject: Re: [cisco-voip] WAN failure in call manager
>
> to be creative one could write an EEM script to monitor for gateway losing
> connectivity to mgcp call agent and then implement an ACL blocking all ip
> connectivity from the phone subnet toward the CM servers.  that would
> effectively have the router control the phone rehome as well.
>
> /wes
>
> On Thursday, December 10, 2009 5:54:30 PM, Lelio Fulgenzi
> <lelio at uoguelph.ca> <lelio at uoguelph.ca> wrote:
>
> Good point Wes. That's what I was trying to say with respect to the last
> paragraph, but reading it again, I didn't make that point clear.
>
> Yes, the gateway does maintain connectivity for it's local ports (PRI, FXS,
> etc) and when it looses connectivity it triggers it's local ports to
> register via SRST to itself (or another SRST router).
>
> However, regardless of that, even if a router can still talk to the CUCM
> cluster, it will accept SRST registrations from phones. (see last message
> sent).
>
> But I love how you manage to start with "it depends.... " ;)
>
> ---
> Lelio Fulgenzi, B.A.
> Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
> (519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> "Bad grammar makes me [sic]" - Tshirt
>
>
> ----- Original Message -----
> From: "Wes Sisk" <wsisk at cisco.com> <wsisk at cisco.com>
> To: "Karen Cheng" <kaz.cheng at gmail.com> <kaz.cheng at gmail.com>
> Cc: "Lelio Fulgenzi" <lelio at uoguelph.ca> <lelio at uoguelph.ca>,
> cisco-voip at puck.nether.net, "anand" <anand.eee at gmail.com><anand.eee at gmail.com>
> Sent: Thursday, December 10, 2009 5:45:03 PM GMT -05:00 US/Canada Eastern
> Subject: Re: [cisco-voip] WAN failure in call manager
>
> it depends.
>
> For MGCP functionality the gateway is monitoring CM.  When failure is
> detected router follows the configured fallback apllication, usually h.323
>
> http://www.cisco.com/en/US/docs/voice_ip_comm/cusrst/admin/srst/configuration/guide/srs_wlan.html#wp1351962
>
> That is only for the gateway though.
>
> Phones monitor CM connecvity. When phone loses connectivity to CM they
> attempt to register with SRST router.  When they register they tell the
> router about their configuration.
>
> To that end it is both phone initiated and gateway initiated.  The gateway
> does not control all logic, nor does the phone control all logic.
>
> /Wes
>
> On Thursday, December 10, 2009 5:32:16 PM, Karen Cheng
> <kaz.cheng at gmail.com> <kaz.cheng at gmail.com> wrote:
>
> Hi Lelio,
>
> I don't believe that part about the phone triggering the SRST function is
> true. From memory I believe the SRST router is the one that detects the WAN
> failure in which after a certain amount of time (dependent on how many
> servers in the CM cluster) it reconfigures itself to be the call agent
> instead. It then also continues to monitor connectivity to the CM cluster
> and once backup will again wait (dependent on how it is configured, wait
> until no calls are active etc) before handing the call agent functions back
> to the CM cluster.
>
> I may be wrong though.
>
> Karen
>
> On Fri, Dec 11, 2009 at 8:21 AM, Lelio Fulgenzi <lelio at uoguelph.ca> wrote:
>
>>  Correct, during the SRST mode, the CUCM cluster is not controlling
>> anything. The phones register to the SRST router using a "simplified"
>> configuration they store in memory. The tell the router what DNs it is
>> supposed to have, and the router configures the appropriate dial-peers. Then
>> using the dynamic dial peers it can call other phones, or using the static
>> dial-peers (ones you program) a phone can call off-net using PSTN.
>>
>> Interesting thing is this, SRST is "always on" waiting for a device to
>> register to it. The device is what controls when it talks to the SRST router
>> or not. That's how you can test registering devices to the router when the
>> WAN really isn't down.
>>
>> It also means that if there is some way or scenario that your phones may
>> not be able to talk to CUCM, but your router can, you will have phones that
>> can call each other, but not out the PSTN because the gateways are still
>> registered to CUCM. That is, of course, if you have MGCP gateways. If you
>> have H323 gateways, I think it's a moot point.
>>
>> Of course, I could be wrong on one or two points, and would be happy to
>> learn something new. ;)
>>
>>
>>
>> ---
>> Lelio Fulgenzi, B.A.
>> Senior Analyst (CCS) * University of Guelph * Guelph, Ontario N1G 2W1
>> (519) 824-4120 x56354 (519) 767-1060 FAX (JNHN)
>> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> "Bad grammar makes me [sic]" - Tshirt
>>
>>
>>
>> ----- Original Message -----
>> From: "anand" <anand.eee at gmail.com>
>> To: cisco-voip at puck.nether.net
>> Sent: Thursday, December 10, 2009 5:15:00 PM GMT -05:00 US/Canada Eastern
>> Subject: Re: [cisco-voip] WAN failure in call manager
>>
>> Hi,
>>
>> I have been breaking my head to understand the exact functions of SRST.
>> During the WAN failure, SRST router takes PSTN path.My question is during
>> this time will the call manager controls the call or Call Manager is
>> completely out of operation(I mean it does not take any part in the call
>> control on the PSTN path).
>>
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