Destination Host Unreachable Reason Solution Verification

Root Cause: It is unable to find out DESTINATION HOST.
REASON:
1) Check the Local Ethernet Port driver is updated properly or not.
2) Confirm Cable is connected properly to the corresponding device.
3)Maintain the same Network.
Before Read Comparison of Destination Host Unreachable and Request Time Out.
Trouble shooting commands.
ethtool -i, mii-tool -v, ping -R , route ,
Verification Command
tcpdump, arp,netstat,nmap,

1)Check whether Ethernet Port driver is updated properly or not.
# ethtool -i eth0
driver: e1000e
version: 1.3.10-k2
firmware-version: 5.11-2
bus-info: 0000:04:00.0
In your current local OS. If corresponding Ethernet driver is not updated properly, then boot from live OS - ubuntu - Red hat Enterprise Linux(rescue mode), Once booted as live CD then it is automatically detect and deploy the Ethernet driver,
So from this point, we can find out the Driver-Version-Firmware-version for then we can install these same Ethernet driver version to our required Production os.
b)After driver installed properly, from ethtool we can Verify the Ethernet device status

# ethtool eth0
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
100baseT/Half 100baseT/Full
1000baseT/Full
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
Supports Wake-on: pumbg
Wake-on: g
Current message level: 0x00000001 (1)
Link detected: yes
speed-port-Link detected Status.
2)Confirm Cable is connected properly or not to the corresponding Ethernet device.
# mii-tool
SIOCGMIIREG on eth0 failed: Input/output error
eth0: negotiated 100baseTx-FD flow-control, link ok
SIOCGMIIREG on eth1 failed: Input/output error
eth1: no link
eth2: no link
eth3: no link
# mii-tool -v eth0
SIOCGMIIREG on eth0 failed: Input/output error
eth0: negotiated 100baseTx-FD flow-control, link ok
product info: vendor 00:aa:00, model 56 rev 0
basic mode: autonegotiation enabled
basic status: autonegotiation complete, link ok
capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control
link partner: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD flow-control

a) Through this output we can confirm whether cable is connected properly to the corresponding device.
3)Maintain the Same Network for Local host and the Remote Host Network IP.

VERIFICAITON METHOD
1)# ping -R 20.0.0.8 [Display Routing Tack]
PING 20.0.0.8 (20.0.0.8) 56(124) bytes of data.
64 bytes from 20.0.0.8: icmp_seq=1 ttl=64 time=0.220 ms
RR: 20.0.0.9
20.0.0.8
20.0.0.8
20.0.0.9
64 bytes from 20.0.0.8: icmp_seq=2 ttl=64 time=0.217 ms (same route)
64 bytes from 20.0.0.8: icmp_seq=3 ttl=64 time=0.215 ms (same route)
a) Record_routing track & display router sending and receiving IP.
2)Monitor the Ethernet Device
# tcpdump -i eth0
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
20:17:37.310618 arp who-has 20.0.0.8 tell 20.0.0.9
20:17:37.310852 arp reply 20.0.0.8 is-at b4:99:ba:a2:a3:c2 (oui Unknown)
20:17:37.310860 IP 20.0.0.9 > 20.0.0.8: ICMP echo request, id 45333, seq 1, length 64
20:17:37.311095 IP 20.0.0.8 > 20.0.0.9: ICMP echo reply, id 45333, seq 1, length 64
-t tcp – udp –a all –I interface –p process id –n display only number(host&ip)
3) What are port are opening and how is it communicate with remote system.

# netstat -tuap
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 *:sift-uft *:* LISTEN 2973/rpc.mountd
tcp 0 0 *:exec *:* LISTEN 2919/xinetd
tcp 0 0 localhost.localdomain:2208 *:* LISTEN 2883/hpiod
tcp 0 0 *:nfs *:* LISTEN -
tcp 0 0 *:login *:* LISTEN 2919/xinetd
tcp 0 0 *:shell *:* LISTEN 2919/xinetd
tcp 0 0 *:wbem-https *:* LISTEN 3260/cimserver
tcp 0 0 *:vce *:* LISTEN 3457/ricci
tcp 0 0 *:1001 *:* LISTEN 2941/rpc.rquotad
tcp 0 0 *:rsync *:* LISTEN 2919/xinetd
4)Find the neighbor System IP & MAC Address.
# arp
Address HWtype HWaddress Flags Mask Iface
20.0.0.8 ether B4:99:BA:A2:A3:C2 C eth0
5)Possibility for Network accessibility.

# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.154.0.0 * 255.255.255.0 U 1 0 0 eth0
192.168.1.0 * 255.255.255.0 U 1 0 0 eth1
151.0.0.0 10.154.0.100 255.0.0.0 UG 0 0 0 eth0
NOTE: U route is up G specified gateway should be used.
Accessible Network.
1)10.154.0.0/255.255.255.0
2)192.168.1.0 /255.255.255.0
3)151.0.0.0/255.0.0.0 Via 10.154.0.100

TRACE ROUTE COMMAND RESULT
1)Using traceroute we can find out what are the hosts are there in between Master and server.
2)Trouble shoot the problem,How is it communicate While Pinging if we are not getting any proper Result or Error Message like ( Destination Host Unreachable or Request Time Out). For then we can use traceroute result we can find out the root cause of the issue.
Sample Result
# traceroute 63.251.XX.XX
traceroute to 63.251.237.22 (63.251.237.22), 30 hops max, 40 byte packets
1 D-Link.Home (192.168.1.1) 0.563 ms 0.759 ms 1.001 ms
2 59.90.146.1 (59.90.146.1) 24.734 ms 26.216 ms 29.467 ms
3 (218.248.174.202) 31.210 ms 34.450 ms 34.687 ms
4 59.163.206.161.static.chennai.vsnl.net.in (59.163.206.161) 37.684 ms 41.151 ms 41.145 ms
5 ix-4-2.tcore1.CXR-Chennai.as6453.net (180.87.36.9) 304.999 ms 305.239 ms 306.215 ms
6 if-3-3.tcore2.CXR-Chennai.as6453.net (180.87.36.6) 340.942 ms if-5-2.tcore1.SVW-Singapore.as6453.net (180.87.12.53) 362.725 ms if-3-3.tcore2.CXR-Chennai.as6453.net (180.87.36.6) 339.957 ms
7 if-5-2.tcore2.SVW-Singapore.as6453.net (180.87.15.69) 386.936 ms 317.557 ms if-2-2.tcore2.SVW-Singapore.as6453.net (180.87.12.2) 317.039 ms
8 if-7-2.tcore2.LVW-LosAngeles.as6453.net (180.87.15.26) 324.010 ms 300.743 ms 313.030 ms
9 if-2-2.tcore1.LVW-LosAngeles.as6453.net (66.110.59.1) 346.784 ms 334.775 ms 341.771 ms
10 192.205.35.129 (192.205.35.129) 341.758 ms 335.006 ms 350.735 ms
11 cr1.la2ca.ip.att.net (12.122.128.30) 258.755 ms 277.004 ms 270.969 ms
12 cr1.sffca.ip.att.net (12.122.3.121) 289.452 ms 266.453 ms 262.451 ms
13 cr83.sffca.ip.att.net (12.123.15.110) 268.189 ms 273.418 ms 277.663 ms
14 12.122.137.25 (12.122.137.25) 221.607 ms 220.103 ms 245.593 ms
15 12.248.24.134 (12.248.24.134) 224.110 ms 227.361 ms 236.857 ms
16 * * *
17 * * *

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