Cisco 877 and 887 frequently drop LAN for 8 seconds

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  • jimwillsher
    Member
    #164618

    Hello all

    I have a strange but really annoying problem with my C877. I have swapped it with another 877 and the problem persists, and I’ve also tried an 887VA with a comparable config and the same problem happens there too.

    5 or 6 times each day the LAN drops. This means I lose VPN connections on any of the computers on the LAN, web pages time out, etc. It happens every day.

    I have swapped routers, swapped switches, tried various 12.4 versions and various 15.x versions, on 877 and 887VA routers.

    If I have a continuous ping (ping -t x.x.x.x) from a PC on the LAN to google’s DNS servers (8.8.8.8) I see this:

    Reply from 8.8.8.8: bytes=32 time=33ms TTL=47
    Reply from 8.8.8.8: bytes=32 time=33ms TTL=47
    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Reply from 8.8.8.8: bytes=32 time=34ms TTL=47
    Reply from 8.8.8.8: bytes=32 time=33ms TTL=47
    Reply from 8.8.8.8: bytes=32 time=33ms TTL=47
    Reply from 8.8.8.8: bytes=32 time=33ms TTL=47

    I get this whichever PC I do the ping from. I’ve also changed network switches so I know it’s not the switch (continuous pings to other devices on the LAN always work correctly with no interruption).

    When the problem happens, pings to the router (192.168.1.1) also fail:

    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Request timed out.
    Reply from 192.168.1.1: bytes=32 time=2ms TTL=255
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=255

    But strangely, the internet connection is NOT dropping. I can prove that in two ways. Firstly, a continuous ping from a remote site back to this router across the WAN never drops:

    Reply from 11.22.33.444: bytes=32 time=44ms TTL=251
    Reply from 11.22.33.444: bytes=32 time=62ms TTL=251
    Reply from 11.22.33.444: bytes=32 time=43ms TTL=251
    Reply from 11.22.33.444: bytes=32 time=45ms TTL=251
    Reply from 11.22.33.444: bytes=32 time=157ms TTL=251
    Reply from 11.22.33.444: bytes=32 time=43ms TTL=251
    Reply from 11.22.33.444: bytes=32 time=43ms TTL=251

    Also, sh caller shows that the WAN didn’t drop:

    Cisco877#sh caller
    Active Idle
    Line User Service Time Time
    vty 2 root VTY 00:09:46 00:00:00
    Vi3
    PPPoATM 5d17h 00:00:08
    Cisco877#

    I’m at a complete loss. Can anyone help please? Either to sggest the cause or to suggest appropriate diagnostics steps.

    My config is attached

    Many thanks

    Jim

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