I have a client with several offices that we have IPsec tunnels connecting all offices. Today, I attempted to setup one of the owners home offices. I put his DSL modem(Netgear modem), in bridging mode and setup PPPoE client on the 450. It authenticates and gets out just fine. However, it disconnects constantly losing it authentication until it negotiates again. Any ideas? Thanks!

Use MikroTik hardware (put one RB450 after the Netgear), then ask help on MikroTik user's forum, or contact MikroTik support,

or go to Netgear support forum.

The RB450 is what I am referencing in regards to the PPPoE issues. It is behind the Netgear. With just the Netgear in place doing the PPPoE it is fine. As soon as I put the 450 in place doing PPPoE, it becomes incredibly flaky.

If You put pppoe-client on ethernet interface instead of bridge, do so.
set pppoe-client od that bridge and set following

int bri set admin-mac=xx:xx:xx:xx:xx:xx

int bri set automac=no

on that bridge.
it's kind of tweak should fix disconnection.