2 weeks ago  I replaced our ubiquity router with the ER605 V2.6.

All but SIP calls work perfectly.

On the other hand the SIP calls now have a delay rampup of RTP traffic.

The first 30 seconds after call setup there is no audio at all (both sides are muted) and afterwards the connection is clear.

However the muted first 30 seconds makes the correspondent hang up.

This situation is consistent for every call.

As a result, because we are using the ER605 we lost business.

So I had no option but remove the ER605 and reinstall the old ubiquity router.

After that, SIP calls were back to normal.

So the linksys router is not usable with IP phones..

p.s. Our SNOM ip hones are connected with a grandstream UCM6202 PBX