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duplicate udp nat entries


We have a NAT issue at our office. Every now and then we lose our SIP registration.  When that happenes and I use the show ip nat translation command I see two udp nat entries with the same inside global and outside global address+port. I anonymised the inside global address. After I use the clear ip nat * command the duplicate entries are gone and two inside global addresses with two different port numbers are used. I found a similar but different problem: which describes the use of duplicate udp entries for different outside global addressses.

Pro Inside global         Inside local          Outside local         Outside global

udp 195.191.X.X:1037

udp 195.191.X.X:1037

IOS version:

Cisco IOS Software, C1900 Software (C1900-UNIVERSALK9-M), Version 15.1(3)T, RELEASE SOFTWARE (fc1)

Does anyone know if this is a know bug, if there is a workaround, if the bug is solved in a newer IOS version?

Kind regards,


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