Destination Net Unreachable

Good Morning,

This question has been asked and I have searched through most of the postings, but unfortunitly i have not found the solution so that is why I am posting this message.

The company I work for has quite a few locations, and every few weeks some of our satilite locations, get a Destination Host Unreachable when they try to ping a particular PC on our network.

We are running Linux, Ubuntu to be exact.

Example: One of our servers in location A is setup with a ip address of They can ping every PC/Server in subnet 192.168.27.X except our terminal server which is When they try to ping it they get this:
PING Hydra3.Domain ( 56(84) bytes of data. destination net unreachable destination net unreachable

The wierd thing is that this clears up within 24 hours.

I talked to a friend and he suggested I look at the routing table, but everything looks ok.

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface    *        U     0      0        0 eth1
link-local      *          U     1000   0        0 eth1
default         UG    100    0        0 eth1

Any help would be greatly appreciated, unfortunitly because this is an intermittent problem, it is hard to troubleshoot, since it is working right now.
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nociSoftware EngineerCommented:
'apt-get install tcptraceroute'
'apt-get install traceroute'
should do the trick according to quick look on the [k]ubuntu site.

It does mean that the system doesn't known how to reach the
network 192.168.27.???
and the network is NOT locally connected to the system either as it would return Destination Host unreachable.
so the network looks a bit like

You (...15.2 -> ...15.1 ==> 30.1 ??> 27.76)

Please investigate the system for routing / connection troubles.
nociSoftware EngineerCommented:
PING Hydra3.Domain ( 56(84) bytes of data. destination net unreachable

You need to look at a lot of routing tables.....
on this system (appearantly has an address in 192.168.19.??, from 2-254).
What btw is the translation of link-local.. at it's netmask is rather large.
netstat -rn would tell you the real address.  (doesn't look like 192.168.15...)
But ok.

From system x ( sends to the next HOP (depending on routing tables) if link local != => the next hop is some system
that will forward to ??? to which tells you that it cant reach the network containing

Now you have to look on at the routing tables to find out what it will do with packets being sent to 192.168.27.???
Also look at the NAT translations that may heppen on the road.

First draw yourself a picture of your net and what route you would have expected it to take.
An aid here might be traceroute as that will should you how routing is done at the individual nodes. If possible to get tcptraceroute than use that with the right portnumber for your terminal service than the packets would even take the right route if some NAT is involved.
philtukeyAuthor Commented:
My apologies, I accidently listed the netstat for the wrong server. Here is the correct netstat -rn for the 15.X server in question.

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface    *        U     0      0        0 eth1
link-local      *          U     1000   0        0 eth1
default         UG    100    0        0 eth1
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philtukeyAuthor Commented:
I am new at Linux so how would go look at in the routing table? Apparently these servers do not have traceroute installed, how do I install that onto the linux servers? Where would I go to find NAT information?
nociSoftware EngineerCommented:
I run gentoo myself but that only means the package manager is different, I thought apt-get was the tool for debian derived distro's.
'apt-get traceroute' maybe?
What you show is 'netstat -r'  which shows the default as default.
'netstat -rn' should show default as
I hope that link-local actually is (can be found in /etc/networks).
because you would have a rather "interesting" setup if it is

And is logging on to possible to try to investigate there what the routing looks like? netstat -rn from that system?
philtukeyAuthor Commented:
I ran netstat -rn and that is what I got.

I will try to run 'apt-get traceroute'
philtukeyAuthor Commented:
When I run apt-get traceroute and got E: Invalid operation traceroute.

philtukeyAuthor Commented:
Here is a better log if what I recieved last night when I tried to ping from
4 packets transmitted, 3 received, 25% packet loss, time 3006ms
rtt min/avg/max/mdev = 220.843/512.429/796.577/235.102 ms
root@ziserv:~# ping
PING ( 56(84) bytes of data.
From icmp_seq=3 Destination Net Unreachable
From icmp_seq=4 Destination Net Unreachable
From icmp_seq=6 Destination Net Unreachable
From icmp_seq=7 Destination Net Unreachable
From icmp_seq=8 Destination Net Unreachable
From icmp_seq=9 Destination Net Unreachable

--- ping statistics ---
9 packets transmitted, 0 received, +6 errors, 100% packet loss, time 8005ms


philtukeyAuthor Commented:
The reason I left it open is because we are waiting for the problem to come back. It comes and goes randomly. So it is hard for me to troubleshoot it, when it working.
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