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Voip Traffic through ASA 5505 (8.3)

Hi Guys,

I have a quick question.

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.

Can anyone see any problem with this?


Cisco Employee

Re: Voip Traffic through ASA 5505 (8.3)

Sounds good to me.  Pls. let us know if you see any problem once you implement it.