We have two offices, each with a 100Mbit leased line. Both offices have an NSA3600 (HA pair) with a site-to-site VPN link connecting the two. We' recently introduced a 1Gbit leased line at each office. Initial speed tests show we're getting around 800-900Mbps up and down at both offices.
We updated the site-to-site VPN policies to use the 1Gbit links, however, users soon began to report performance issues, such as: lag and brief disconnections with their RDP sessions (between sites) as well jitter on voip calls between sites. If we adjust the vpn policies back so they're using the 100Mbit link the issue goes away. The SonicWall's are on the latest firmware and we've disabled all security services on the VPN zone. We also tried adjusting the interface mtu to optimal values but this didnt help. We have a support case open with SonicWall...