Issue with fragmented UDP is NAT routers that cannot forward second and follow fragments to SIP device.
Connection tracking must be enabled on router.

https://serverfault.com/questions/533704/why-is-iptables-rejecting-the-second-and-subsequent-fragments-of-an-allowed-pack

пн, 1 апр. 2019 г. в 18:44, Fred Posner <fred@palner.com>:
On 4/1/19 11:30 AM, Richard Fuchs wrote:
>>
>> of course, you're hoping that the fragmented packets arrive in order.
>>
> That really makes no difference. The network stack takes care of
> reassembling the fragments no matter what order they arrive in.
>
> Issues only arrive from broken routers or firewalls, or if you have to
> deal with packet loss.
>
> Cheers
>

I blame my initial response on a lack of coffee and attention to
Kamailio Managed Cloud ;)

--fred

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