Hostname changes after replies restart

[John Bradshaw]

iputils-ping:
  Installed: 3:20121221-4ubuntu1.1
  Candidate: 3:20121221-4ubuntu1.1
  Version table:
 *** 3:20121221-4ubuntu1.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     3:20121221-4ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

LSB Version: core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:core-4.1-amd64:core-4.1-noarch:security-4.0-amd64:security-4.0-noarch:security-4.1-amd64:security-4.1-noarch
Distributor ID: Ubuntu
Description: Ubuntu 14.04.2 LTS
Release: 14.04
Codename: trusty

Expected: Returned FQDN and IP should be that of box sending ICMP errors/replies.

Actual: Getting the FQDN and IP of an intermediate router, even though replies are coming from another host.

Situation:
Pinged a remote box which was restarting. Initially got ICMP from the intermediate router but when pings restarted the FQDN & IP are that of the router, not the pinged host:

Log:
$ ping edi
PING edi.sub.domain.tld (x.y.1.131) 56(84) bytes of data.
From router0.sub.domain.tld (x.y.1.1) icmp_seq=25 Destination Host Unreachable
From router0.sub.domain.tld (x.y.1.1) icmp_seq=55 Destination Host Unreachable
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=84 ttl=63 time=10564 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=95 ttl=63 time=0.222 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=96 ttl=63 time=0.185 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=97 ttl=63 time=0.156 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=98 ttl=63 time=0.136 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=99 ttl=63 time=0.091 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=100 ttl=63 time=0.134 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=101 ttl=63 time=0.157 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=102 ttl=63 time=0.162 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=103 ttl=63 time=0.231 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=104 ttl=63 time=0.221 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=105 ttl=63 time=0.192 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=106 ttl=63 time=0.159 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=107 ttl=63 time=0.213 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=108 ttl=63 time=0.206 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=109 ttl=63 time=0.160 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=110 ttl=63 time=0.186 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=111 ttl=63 time=0.187 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=112 ttl=63 time=0.227 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=113 ttl=63 time=0.250 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=114 ttl=63 time=0.195 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=115 ttl=63 time=0.255 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=116 ttl=63 time=0.200 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=117 ttl=63 time=0.248 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=118 ttl=63 time=0.256 ms
64 bytes from router0.sub.domain.tld (x.y.1.1): icmp_seq=119 ttl=63 time=0.181 ms
^C
--- edi.sub.domain.tld ping statistics ---
119 packets transmitted, 26 received, +2 errors, 78% packet loss, time 118718ms
rtt min/avg/max/mdev = 0.091/406.521/10564.744/2031.644 ms, pipe 30

$ ping edi
PING edi.sub.domain.tld (x.y.1.131) 56(84) bytes of data.
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=1 ttl=63 time=0.208 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=2 ttl=63 time=0.168 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=3 ttl=63 time=0.207 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=4 ttl=63 time=0.201 ms
^C
--- edi.sub.domain.tld ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 2999ms
rtt min/avg/max/mdev = 0.168/0.196/0.208/0.016 ms

$ ping edi
PING edi.sub.domain.tld (x.y.1.131) 56(84) bytes of data.
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=1 ttl=63 time=0.167 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=2 ttl=63 time=0.213 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=3 ttl=63 time=0.236 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=4 ttl=63 time=0.234 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=5 ttl=63 time=0.171 ms
64 bytes from edi.sub.domain.tld (x.y.1.131): icmp_seq=6 ttl=63 time=0.199 ms
^C
--- edi.sub.domain.tld ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5001ms
rtt min/avg/max/mdev = 0.167/0.203/0.236/0.029 ms

Setup:
1. Hosts "me" (x.y.2.60) and "edi" (x.y.1.131) connected via router (x.y.1.1 and x.y.2.1)
2. Disconnect or reboot remote box "edi"
3. Start ping.
4. Watch for ICMP Destination Host Unreachable from router
5. Connect (or wait for reboot to complete) remove box "edi".
6. Note that ICMP replies will start but show FQDN & IP of intermediate router, not the pinged host.

Think the router FQDN is being cached and returned in error.