There are four NE40 routers in 2 different sites (Router A & B in the first city - Router C & D in the second city)
The topology is A to C with 4 E1 are bundle (interface Mp-group)
B to D with 4 E1 are Bundle (interface Mp-group)(as redundant)
when traffic are in this links each 3 to 5 minutes we have time out in network and ospf routing protocol recalculat again in each period time.
we had time out in ping after around each 30 packet and all network segments are disconnected
after checked all NE40 configurations and debugging the ospf function we find a problem in transmission link like this:
one of E1 in the bundel in master group( Router A to C) is connect to slave group (Router B to D) mistakenly.
so first shut it down its serial interface and then repair that mistake.
before configure the serial ports we should check physically