So I've had SIP NAT'ed over a 891 for years and years. Then I do a router upgrade to a ISR 4331 and copy the config across modifing the bits that need to be changed and I thought the everything was working fine.
Then I get told by the users that they can't transfer between the phones (SPA303's) and I've tried everything I can think of like disabling ALG for UDP and TCP and removing the ZBF for the VOIP VLAN and still nothing, transfers still fail.
Anybody know of anything special that the 4331's are doing to the INVITE packets, or is it just borked firmware?
4331 is currently running 3.13.4.S.154-3.S4-ext.SPA
Thank you!
