Can Ping Switch but Can't Ping Rtr (behind it)

Discussion in 'Cisco' started by Bob Simon, Nov 5, 2003.

  1. Bob Simon

    Bob Simon Guest

    I am at home (68.0.56.75) and can ping my company's 2924 switch
    (public address: x.y.34.2) but not a 2500 lab router behind it (public
    address: x.y.34.4). However, if I telnet to the switch, I can then
    ping or telnet to the 2500. I am able to ping all the other devices
    attached to the switch from home, why not the 2500?

    The config for the switch and router ports follow:
    SWITCH
    FastEthernet0/19 is up, line protocol is up
    Hardware is Fast Ethernet, address is 0030.7bdd.8c13 (bia
    0030.7bdd.8c13)
    Description: Cisco 2500
    MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
    reliability 255/255, txload 1/255, rxload 1/255
    Encapsulation ARPA, loopback not set
    Keepalive not set
    Auto-duplex (Half), Auto Speed (10), 100BaseTX/FX
    ARP type: ARPA, ARP Timeout 04:00:00
    Last input 00:00:58, output 00:00:01, output hang never
    Last clearing of "show interface" counters 01:11:12
    Queueing strategy: fifo
    Output queue 0/40, 0 drops; input queue 0/75, 0 drops
    5 minute input rate 0 bits/sec, 0 packets/sec
    5 minute output rate 5000 bits/sec, 10 packets/sec
    768 packets input, 68420 bytes
    Received 283 broadcasts, 0 runts, 0 giants, 0 throttles
    0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
    0 watchdog, 71 multicast
    0 input packets with dribble condition detected
    44727 packets output, 7433576 bytes, 0 underruns
    0 output errors, 22 collisions, 0 interface resets
    0 babbles, 0 late collision, 2 deferred
    0 lost carrier, 0 no carrier
    419 output buffer failures, 0 output buffers swapped out

    ROUTER
    #show int e0
    Ethernet0 is up, line protocol is up
    Hardware is Lance, address is 0000.0c5d.1126 (bia 0000.0c5d.1126)
    Internet address is x.y.34.4 255.255.255.0
    MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec, rely 255/255, load
    1/255
    Encapsulation ARPA, loopback not set, keepalive set (10 sec)
    ARP type: ARPA, ARP Timeout 4:00:00
    Last input 0:00:00, output 0:00:00, output hang never
    Last clearing of "show interface" counters 0:01:49
    Output queue 0/40, 0 drops; input queue 23/75, 0 drops
    5 minute input rate 8000 bits/sec, 13 packets/sec
    5 minute output rate 1000 bits/sec, 3 packets/sec
    2323 packets input, 142399 bytes, 0 no buffer
    Received 2234 broadcasts, 0 runts, 0 giants
    0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
    0 input packets with dribble condition detected
    80 packets output, 6223 bytes, 0 underruns
    0 output errors, 0 collisions, 0 interface resets, 0 restarts
    0 output buffer failures, 0 output buffers swapped out

    Also, debug ip packet on the switch shows that it receives icmp
    packets from my home pc to it, but not when I ping the router. What
    could cause this?
     
    Bob Simon, Nov 5, 2003
    #1
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  2. Bob Simon

    Rik Bain Guest

    ip default-gateway, IIRC, is only for traffic from the router (i.e. TFTP,
    telnet, et al.) when ip routing is disabled.

    Rik
     
    Rik Bain, Nov 5, 2003
    #2
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  3. Bob Simon

    Bob Simon Guest

    I have some more info:
    I can successfully ping both the switch and router from another
    computer that is directly connected to the switch. I cannot ping the
    router from another host that is off-net.

    Thinking that perhaps my ISP's managed router (not under my control)
    is blocking x.y.34.4, I changed the router's IP address to x.y.34.14.
    This did not help.

    Anyone got any other ideas for me to try?
     
    Bob Simon, Nov 6, 2003
    #3
  4. Bob Simon

    Scooby Guest

    Try a trace (tracert in windows) from your pc to the router and then a trace
    from the router to your pc - that will at least tell you where the packets
    are getting dropped or routed improperly.
     
    Scooby, Nov 6, 2003
    #4
  5. Bob Simon

    Bob Simon Guest

    I found my problem! I was missing the following statement in the
    router:
    ip route 0.0.0.0 0.0.0.0 x.y.34.1 1

    I had this instead (which did not work):
    ip default-gateway x.y.34.1

    I thought that 0.0.0.0/0 WAS the default gateway. I guess not!
    What's the difference between these two statements?
    Bob

     
    Bob Simon, Nov 6, 2003
    #5
  6. :I found my problem! I was missing the following statement in the
    :router:
    :ip route 0.0.0.0 0.0.0.0 x.y.34.1 1

    :I had this instead (which did not work):
    :ip default-gateway x.y.34.1

    :I thought that 0.0.0.0/0 WAS the default gateway. I guess not!
    :What's the difference between these two statements?

    If I recall correctly, default-gateway is the gateway of last resort
    if all the routing protocols fail.
     
    Walter Roberson, Nov 6, 2003
    #6
  7. Check the routing on the 2500 - does it have a return route to your
    home (68.0.56.75) address or a default route? If you can't ping the
    2500 from anywhere other than the network that it is directly
    connected to, I reckon it hasn't got the necessary routing statements.

    Pete
     
    Pete Mainwaring, Nov 6, 2003
    #7
  8. Bob Simon

    Andre Beck Guest

    The "ip default-gateway" statement is only significant when you configure
    "no ip routing", whereas the explicit declaration of a 0.0.0.0/0 static
    route is only significant when you configure "ip routing".
     
    Andre Beck, Nov 9, 2003
    #8
  9. Bob Simon

    John Lamar Guest

    Yes, you need a default route for all other traffic other than your
    directly connected network... however the 2500 knows where the switch
    is so you are in good shape.

    The problem is between you and your switch. Actually that doesn't make
    sense. Your isp gets you to the switch, the x.y.3.0 network....
    something before that switch knows about this network also. Turn on the
    appropriate routing protocols on both devices and you should be in good
    shape.

    If the switch is then connected to a router or gateway on the other
    side that allows it on the internet make that path (that adapter's
    network) the default route.
     
    John Lamar, Jan 19, 2005
    #9
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