TTL expired in transit switch issue

What is the source IP address and destination IP address of the pings?

both in same subnet:

Host 10.10.1.100
destination 10.10.12.33
SM 255.255.0.0

If what you're describing is correct then the behavior is not really possible. The TTL field is only decremented by a router (layer 3 device). If the source is 10.10.1.100/16 and the destination is 10.10.12.33/16, they hosts are on the same network and no router is needed. Which means the TTL isn't being decremented so there could be no TTL expired.

Unless the sending host is transmitting with a TTL of zero which isn't likely either.

I suspect there's more to your network than meets the eye. Can you provide configs of the network devices and indicate which ports the 10.10.1.100 and 10.10.12.33 hosts are connected to.

exactly my thought... there is no hop on the same subnet. Both hosts are connected to ports on Vlan 10 on separate switches. I expected to get a request timed out but not so. All switches have routing on Vlan 10 enabled. The dell 8024 is a new, different animal to me compared to the HPs. The previous image shows the basic topology. 8024 startconfig attached.
startup-config

I have no idea why a switch (or router) would respond with a ICMP TTL exceeded message for a device on the same network as the sender.

now you know my pain. I can't find anything......

What happens when you do a traceroute? (with the destination on and off)

The device is now online. Tracert has the device going thru the .17 switch?


Tracing route to ricohmpc5502-boe.test.org [10.10.12.33]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  10.10.0.17
  2    <1 ms    <1 ms    <1 ms  ricohmpc5502-boe.test.org [10.10.12.33]

I would double check that HP2910 and 10.10.12.33 both have the subnet mask 255.255.0.0.

Can you also do:

     ping -r 9 ricohmpc5502-boe.test.org

I've seen some weird stuff when not everything has the correct subnet mask

both devices /16


C:\Users\samuels>ping -r 9 ricohmpc5502-boe.test.org

Pinging ricohmpc5502-boe.test.org [10.10.12.33] with 32 bytes of data:
Reply from 10.10.12.33: bytes=32 time<1ms TTL=255
    Route: 10.10.12.33
Reply from 10.10.12.33: bytes=32 time=24ms TTL=255
    Route: 10.10.0.17 ->
           10.10.12.33
Reply from 10.10.12.33: bytes=32 time=1ms TTL=255
    Route: 10.10.0.17 ->
           10.10.12.33
Reply from 10.10.12.33: bytes=32 time=116ms TTL=255
    Route: 10.10.0.17 ->
           10.10.12.33

Could you post the output of an ipconfig (or O/S similar command) from the source host.

Ethernet adapter vEthernet (Virtual Switch):

   Connection-specific DNS Suffix  . :
   Description . . . . . . . . . . . : Hyper-V Virtual Ethernet Adapter #2
   Physical Address. . . . . . . . . : 18-03-73-4F-82-C9
   DHCP Enabled. . . . . . . . . . . : No
   Autoconfiguration Enabled . . . . : Yes
   IPv4 Address. . . . . . . . . . . : 10.10.1.100(Preferred)
   Subnet Mask . . . . . . . . . . . : 255.255.0.0
   Default Gateway . . . . . . . . . : 10.10.0.1
   DNS Servers . . . . . . . . . . . : 10.10.1.35
                                       10.10.1.36
   NetBIOS over Tcpip. . . . . . . . : Enabled

Also from the target host.  To me it looks like one of them may have a subnet mask other than 255.255.0.0.

You may also want to look at all the routing tables in all of the devices.  There may be a device with a entry for 10.10.0.0/24 or 10.10.1.0/24.  Which could also cause weird results.

The printer is connected to a switch down stream. I cleared cache on both switches. After I ping host an entry is written back to the cache. As before the ping request will go to the .17 switch on the first attempt and then .18 for the final 3 attempts?

Did you check the routing tables on everything?

I did. I'm only routing one vlan at this point in time.

I found parameters on routing interface and proxy arp and local proxy arp are indeed checked. If I uncheck and ping host I now get ttl timeout on last resort gateway on the actual router, which is where I thought it should be.

On the dell 8024, the 2 arp settings are enabled by default. Should I just keep the defaults and go with lesson learned? Thanks guys.

Weird.  I personally would not use proxy arp.  Since so many network monitoring products use ping as one way to see if a device is up and to measure latency issues, I would leave it off.

Otherwise your monitoring software will show the device is up when in fact it may not be.

thanks giltjr

To be clear: this seems to be a bug of Dell. The switches must never proxy ARP for a request in the same subnet. Proxy ARP is only useful across subnet boundaries.