It was found problem with big packets forwarding between two NE40 connected through SDH FE media.
If client_1 of one NE40 ping client_2 of second NE40 with big packet size, some ping reply can not reach client_1. (Diagram attached)
<ATC-144-NE40-8>display interface Ethernet 3/0/5
1824163 CRC, 0 errors, 0 overruns
An autonegotiation mismatch of the duplex setting can reduce performance or cause no link. You can identify a duplex mismatch by checking the port statistics for the following errors:
? A port set to half duplex connected to a port set to full duplex shows late collision errors or no link.
? A port set to full duplex connected to a port set to half duplex shows frame check sequence (FCS) errors.
After autonegotiation was enabled on router there was not any problems with big packets.
The IEEE 802.3u autonegotiation protocol manages the switch settings for speed (10 Mbps or 100 Mbps) and duplex (half or full). There are situations when this protocol canincorrectly align these settings, reducing performance. A mismatch occurs when:
? A manually-set speed or duplex parameter is different from the manually set speed or duplex parameter on the attached port.
? A port is in autonegotiate and the attached port is set to full duplex with no autonegotiation.
Engineer need to pay attention to configuration and parameters of equipment while software debugging.
When you change the duplex parameters, be sure that both speed and duplex settings
match. Autonegotiation should be either enabled on both ports or not enabled on both ports.