Up->Down messages related to ip sla icmp-echo when there are noapparent network issues

Discussion in 'Cisco' started by ttripp, Apr 29, 2009.

  1. ttripp

    ttripp Guest

    I am trying to use ip sla with icmp-echo to control the entry of a
    static
    route in the routing table. Currently I am using sla for controling
    two routes, with more
    to come. My sla configuration looks like this:

    ip sla monitor 5
    type echo protocol ipIcmpEcho 10.120.26.5 source-ipaddr 10.120.26.60
    frequency 15
    ip sla monitor reaction-configuration 5 threshold-falling 5000
    threshold-type consecutive
    3
    ip sla monitor schedule 5 life forever start-time now
    ip sla monitor 12
    type echo protocol ipIcmpEcho 10.120.26.12 source-ipaddr 10.120.26.60
    frequency 15
    ip sla monitor reaction-configuration 12 threshold-falling 5000
    threshold-type consecutive
    3
    ip sla monitor schedule 12 life forever start-time now

    ! Lines ommited

    track 5 rtr 5 reachability
    !
    track 12 rtr 12 reachability

    ! Lines omitted

    ip route 10.100.30.0 255.255.255.0 10.120.26.5 track 5
    ip route 10.1.3.12 255.255.255.255 10.120.26.12 track 12

    As I understand it, the way I have this configured the router should
    ping the two
    configured ip addresses every 15 seconds, and if the 5000msec
    threshold is surpassed three
    consecutive times, then reachability is considered "down" and the
    router is removed from
    my table.

    The problem is that I get the following log messages at random times:

    04-29-2009 10:00:23 Paris_-_WAN-PARIS-1_(10.60.10.1) 182: *Apr 29
    14:13:00:
    %TRACKING-5-STATE: 12 rtr 12 reachability Down->Up
    04-29-2009 10:00:13 Paris_-_WAN-PARIS-1_(10.60.10.1) 181: *Apr 29
    14:12:50:
    %TRACKING-5-STATE: 12 rtr 12 reachability Up->Down

    However, monitoring from PRTG shows the ping response times for both
    of these ip addresses
    is in the 100-200msec time, which shouldn't be nearly enough to
    trigger a Down->Up.

    Also, each Down->Up is followed exactly 10 seconds later by an Up-
    happens each and every time. I have four other routers configured the
    same way and they
    also have the same issue, and the same 100-200msec ping time, and the
    same 10 second
    Down->Up/Up->Down cycle.

    Bandwidth utilization on the circuits these pings are going out on
    varies, but the error
    is generated even when traffic is nill.

    So, has anyone seen anything like this before? Thanks.
     
    ttripp, Apr 29, 2009
    #1
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  2. ttripp

    bod43 Guest

    The Down->Up seems back to front to me?
    Surely it is up normally and needs to go Up-> down first?

    You might consider

    debug ip sla event
    debug ip sla error

    to see what the router thinks it is doing.

    These will generate quite a bit of output over time.
     
    bod43, Apr 30, 2009
    #2
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  3. ttripp

    Thrill5 Guest

    I believe that the problem is the you have configured a 5 second timeout,
    and your only polling every 15 seconds. The falling-threshold of 5000 msec
    (5 seconds) means that if the last successful ping occured more than 5
    seconds ago, the sla is down. This number is NOT how long it should wait
    for a response.
     
    Thrill5, Apr 30, 2009
    #3
  4. ttripp

    ttripp Guest

    Thanks. I opened a ticket with TAC and they said the same thing,
    basically. It's fixed now.
     
    ttripp, May 1, 2009
    #4
  5. ttripp

    jlodwick

    Joined:
    Oct 22, 2009
    Messages:
    1
    Likes Received:
    0
    What was Cisco TAC's response?

    ttripp,
    Could you please let me know what Cisco TAC's response was to fix this problem? I'm trying to tweak this like you were and having the same problems you were having. Did they say to increase the falling-threshold and if so to what?

    Thanks,
    Jeff
     
    jlodwick, Oct 23, 2009
    #5
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