I have L3 service from sevice provider.There are Cisco3825 at one side and Cisco1760 at another side. Cisco 3825 have fractional E1 serial interface. Cisco1760 have FE port to SP. FE port of router is connected to FE port of ADSL-modem. Sometime I see that network connectivity is lost. I can't ping 1760 from 3825, VoIP traffic don't pass. This problem disappear itself. I made extended ping from 3825 to 1760 during 2-3 hours. I saw 25% unsuccessfull ping. I changed router on PC with WinXP. I made extended ping now. I saw 100% successfull ping.
How I can resolve this problem?