[cisco-voip] E164 routing loop

[Brian Meade]

You can do things like "no voice hunt unassigned-number" and "no voice hunt
invalid-number" on IOS to keep it from trying more dial-peers.

On Sun, Aug 13, 2017 at 10:47 PM, Ki Wi <kiwi.voice at gmail.com> wrote:

> Hi Group,
> I have encountered this interesting problem on customer PBX. Didn't work
> on live system for a long time but I am pretty sure this shouldn't be a
> default behavior.
>
> When external PSTN caller calls an unassigned number in the DID range,
> CUCM returns with error code 27 ( destination out of order).
>
> This causes the voice gateway to retry other dial-peers.
>
> There's 3 dial-peer which matches this e164 number.
> 1)Dial-peer 100 goes CUCM (longest match, most specific)
> 2)Dial-peer 200 goes CUCM (longest match, most specific)
> 3)Dial-peer 300 goes to PSTN (the destination-pattern is .T)
>
> When dial-peer 100 and 200 "fails", the voice gateway will dial-out to
> PSTN via dial-peer 300. Once again, PSTN route back to the customer VG.
> This causes a routing loop and it can fills up all the available E1
> channels quickly.
>
>
> *Just wondering if anyone encounter the following issue and have a
> explanation to it? Just the engineering side of me want to get down to the
> root cause. *
>
> The CUCM have "stop routing on unallocated number" turns off (false). Just
> in case it matters.
>
> I tried to google around but can't seems to find any article that talks
> about
> 1) dial-peer behaviors (on voice gateway side) - on what error code will
> cisco voice gateway retry other dial-peers?
> 2) why CUCM returns error code 27?
>
> It's a managed service system so I'm unable to do a deep dive
> troubleshooting.
>
> The current workaround introduced is to create a dial-peer 250 with a
> higher preference that matches the DID range and block it.
>
> This means that incoming dialed number will match to 4 dial-peers (100,
> 200, 250 and 300)
>
> After failing on 100 and 200, the call gets block on dial-peer 250.
>
> --
> Regards,
> Ki Wi
>
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>
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