Network topology is as follows: AR18-20 ---- ADSL Modem ---- DSLAM (ISP).
AR18-20 version is VRP3.40F0115. AR18-20 is used as PPPoE client. Phenomena is slow speed and connectivity break-down with modem when downloading files. This happens after few minutes. Dialer interface is still up, but there is no connection with modem.
There is 2 solutions to this problem. One is changing speed on modem if this is supported on modem. Second solution that solves problem is putting ethernet interface on which dialer interface is applied to half-duplex mode.
pppoe-client dial-bundle-number 1
1.1. There is big number of crc errors on ethernet interface on which dialer interface is applied.
1.2. This crc errors can cause both slow speed and lost of connectivity.
1.3. Crc errors usually occur because physical link is damaged or because of problems of synchronization on different ends of link.
1.4. In case of AR18-20 problem is that this router has WAN ethernet port with 10 Mb/s speed that cannot be changed to 100Mb/s or auto-negotiation mode.
1.5. With modems that can not change speed to 10 Mb/s, manually or by auto-negotiation, this leads to described problems.