Why is the MTU for a PPPoE DSL configuration reduced from 1500 bytes to 1492?
- to establish a secure tunnel with less overhead
- to enable CHAP authentication
- to accommodate the PPPoE headers
- to reduce congestion on the DSL link
Explanation: The default maximum data field of an Ethernet frame is 1500 bytes. However, in PPPoE the Ethernet frame payload includes a PPP frame which has also has a header. This reduces the available data MTU to 1492 bytes.
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