I'm setting up an ASA 5505 running 8.3 for someone, they had an 877 that no longer suits there needs so its being replaced with an ASA.
They have some VoIP phones internally. The Voip phones register out to a SIP proxy on the internet, during the registration they send their private IP addresses. The VoIP phones also use NAT keep alive to keep the nat translation in the xlate table.
On the 877 I just had to allow SIP traffic to the outside firewall interface and SIP inspection was on inbound on the inside and outside interface, the inside allowed out all traffic ( not by my choice). This worked fine.
On the ASA, There is a default inspection which inspects SIP, plus an interface inspection for the Phone Vlan that prioritises all traffic from the phone subnet.
I've also allowed SIP traffic targeted to the FW's outside IP from the known SIP proxies public IP. I'm hoping that the NAT keep alives from the phones will keep the nat entries for the phone.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...