Cisco RV220W Router Settings
Posted by Chris Popescu on 24 April 2019 06:46 PM

Known Issues

1. SIP ALG will cause problems if it's enabled, but it can be disabled on at least one of the firmware versions.

2. MTU is set to Auto by default, which can set it to 576, which is too low.  This will cause intermittent phone feature failures & call audio (RTP) to be lost mid-calls.


1. Log into the router.

Go to Firewall > Basic Settings > SIP ALG > Uncheck > Save.

2. If there isn't an option to disable SIP ALG, the IT or a tech-savvy individual will need to call Cisco for help upgrading the router to the latest firmware version.

If the router is running the latest firmware and it still doesn't have the option to disable SIP ALG, then you will need to replace the router with a compatible one.

3. Change the MTU from Auto to one of the options below.

This setting is usually found under Networking > WAN.

Your router may reference 'WAN' as Internet Settings or with slightly different terminology, depending on the firmware:

1500 for Cable

1492 for DSL

FiOS using PPPoE (most pre-2006 FiOS circuits) – 1492

FiOS using DHCP (most post-2006 FiOS circuits) -- 1500

Contact your ISP if you're unsure.

This step is only needed if you have or plan to purchase Polycom phones.

The steps below only apply if you are using the RV220W as the DHCP server:

Go to Networking > LAN > LAN Configuration > Set the following:

Primary DNS Server - "".

Secondary DNS Server - "".

LAN Proxy - DNS Proxy - Uncheck.

Click Save.

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