Limitations

EAP is subject to internal limits. When the E-series router acts as a pass-through between the backend authentication server and the peer, EAP packets traverse the controllers within the router. The size of EAP packets and fragments tends to be larger than the buffer exchange limit—1450 bytes—between the controllers. This intercontroller buffer exchange limit is tuned for the optimal system performance and scalability; also, when stacked over L2TP on LNS, it prevents PPP control packets from causing IP fragmentation and reassembly on the Ethernet downlink. Hence, if EAP is configured as a PPP authentication protocol, then EAP packet or fragment size is affected by the intercontroller buffer exchange limit as follows:

• The MRU value advertised by JUNOSe in the LCP request packet takes the lowest of the following values:
  • the lower layer MRU minus the PPP overhead
  • the configured MRU
  • 1450 bytes
• The MTU value is initialized by JUNOSe to the lowest of the following values:
  • the lower layer MTU minus the PPP overhead
  • the peer MRU
  • 1450 bytes

The MTU value is passed to RADIUS in an Access-Request packet by means of the Framed-Mtu attribute.

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