Ideally all devices on the local network should be the same. However, contrary to popular belief, lowering the MTU on a router is almost useless and may actually create more problems. Selecting the correct MTU size on the PC's NIC is the absolutely, positively, and with no shadow of any doubt the most important setting, because the NIC is where the packet is originally assembled. This is incredibly important to PPPoE connectivity since it requires an additional 8 byte header as compared to PPPoA. If the NIC produces a 1500 byte packet then it must be fragmented to get past the router that is set to 1492 (default router PPPoE setting)or lower. Many people mistakenly think that the NIC and the router will auto negotiate the MTU on the LAN side to 1492 but in fact most routers will pass a 1500 byte packet on the LAN side. The MTU setting set in the router is almost always exclusively for the WAN side connectivity, not the LAN. Therefore the MOST important MTU setting is on the NIC where the packet is originally made. If you have an MTU of 1492 (or lower) on the NIC you could run an MTU of 50,000,000,000,000,000 bytes on the router and the largest packet ever sent to the internet would still only be 1492. But the opposite is not true. If you have a router set at 1492 and a NIC at 1500 and the NIC sends out a 1500 byte packet then it must be fragmented and that's when the trouble starts. Fragmented packets are not always easy to detect and many people do not even realize that they are having a problem but they are. Set it to 1492 and be done with it.

Andy Houtz DSL