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Destination host unreachable линукс

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  1. From 192.168.0.146 icmp_seq=1 Destination Host Unreachable [closed]
  2. 2 Answers 2
  3. What can be the probable reason behind not able to ping?
  4. Why does ARP resolution fail?
  5. Remaining possibilities
  6. «Destination Host Unreachable» and ssh » No route to host»
  7. Destination Host Unreachable

From 192.168.0.146 icmp_seq=1 Destination Host Unreachable [closed]

Want to improve this question? Update the question so it focuses on one problem only by editing this post.

root@prateek-desktop:~# ping 192.168.0.1 PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data. From 192.168.0.146 icmp_seq=1 Destination Host Unreachable From 192.168.0.146 icmp_seq=2 Destination Host Unreachable From 192.168.0.146 icmp_seq=3 Destination Host Unreachable root@prateek-desktop:~# netstat -rn Kernel IP routing table Destination Gateway Genmask Flags MSS Window irtt Iface 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1

What can be the probable reason behind not able to ping ? Firewall has been disabled. 192.168.0.1 is the IP address of my wireless router which is DHCP enabled. The ethernet port to that router has IP address assigned by DHCP. My PC has IP address 192.168.0.146. Both router and PC are having same network. My PC has Default gateway in network settings assigned as 192.168.0.146. My other devices can ping my PC, but my PC can not ping any other device including the router to which my PC is attached directly.

@AfroJoe Interestingly ICMP echo turned off on the far side will not generate this specific output, you wouldn’t get any ICMP reply lines at all. Traditional firewall rules would be the same. This output might happen with an ethernet router configured to only allow certain MAC addresses, if you were pinging that router.

I am not sure, but I think this might happen when you have a conflicting IP address on another device. So that you are actually pinging a different device, not your PC :-). I have edited my answer. I guess this is a very late answer, sorry :-).

2 Answers 2

[edit] My other devices can ping my PC, but my PC can not ping any other device including the router to which my PC is attached directly.

I would check for a conflicting IP address on another device.

(Even though I am not sure your ping results are consistent with this. It does not quite fit my intuition about ARP, and unfortunately I did not find any similar combination in Google Search results. Perhaps there is an additional problem or a different problem. But it is a nice thing to check, and it might help you find some clue).

On your PC, find what the MAC address («hardware address») is. If you run ip link show dev eth1 , the MAC address is the value shown after link/ether .

On one of the other devices, check carefully what MAC address it has cached for your IP, 192.168.0.146. If the other device runs Linux, you can check the ARP cache using ip -4 neigh . If the other device runs Windows, you can check the ARP cache using arp -a (in Windows command line). If it shows a different MAC address for your IP 192.168.0.146, then you were actually pinging a different device, not your PC :-).

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What can be the probable reason behind not able to ping?

Technically, ping showing «Destination Host Unreachable» is a rather specific error message! Your output almost certainly means the ARP resolution is failing. On 192.168.0.146 . It looked like this was the same computer you ran ping on, and you confirmed that in a later edit. In that case, here is how you confirm an ARP issue:

$ ping 172.16.8.2 PING 172.16.8.2 (172.16.8.2) 56(84) bytes of data. From 172.16.8.205 icmp_seq=1 Destination Host Unreachable From 172.16.8.205 icmp_seq=2 Destination Host Unreachable From 172.16.8.205 icmp_seq=3 Destination Host Unreachable ^C --- 172.16.8.2 ping statistics --- 4 packets transmitted, 0 received, +3 errors, 100% packet loss, time 3050ms pipe 4 $ ip -4 neigh 172.16.8.1 dev wlp2s0 lladdr 74:44:01:86:42:d6 REACHABLE 172.16.8.2 dev wlp2s0 INCOMPLETE

Successful ARP resolution involves an exchange like this:

$ sudo tcpdump -n -i wlp2s0 arp or icmp tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on wlp2s0, link-type EN10MB (Ethernet), capture size 262144 bytes . 13:43:49.469349 ARP, Request who-has 172.16.8.1 tell 172.16.8.205, length 28 13:43:49.470046 ARP, Reply 172.16.8.1 is-at 74:44:01:86:42:d6, length 28 13:43:49.852608 IP 172.16.8.205 > 172.16.8.1: ICMP echo request, id 5246, seq 21, length 64 13:43:49.854600 IP 172.16.8.1 > 172.16.8.205: ICMP echo reply, id 5246, seq 21, length 64 13:43:50.853879 IP 172.16.8.205 > 172.16.8.1: ICMP echo request, id 5246, seq 22, length 64 13:43:50.855867 IP 172.16.8.1 > 172.16.8.205: ICMP echo reply, id 5246, seq 22, length 64 ^C 18 packets captured 18 packets received by filter 0 packets dropped by kernel

(observed while running ping, and forcing an ARP refresh using ip neigh flush dev wlp2s0 ).

Note: this interpretation basically only applies to ping . It does not apply when you get a «Host Unreachable» message from a «normal» TCP/IP application like ssh or curl , because that might also mean you received an ICMP error reply such as «Administratively prohibited» (from a firewall). However ping receives and decodes the entire ICMP reply. So ping would tell you that the error was specifically «Administratively prohibited», not just «Host Unreachable».

Also, this Q&A is about IPv4. I have not checked how it could be adapted for IPv6.

Why does ARP resolution fail?

I have one other piece of secret knowledge. Unless your Ubuntu client system was deliberately configured by someone, the address 192.168.0.146 was assigned through an exchange of DHCP packets. Typically this exchange would involve the router, although in other cases it might only involve a Windows Server or other type of server. In this case where the router is the DHCP server or relay, your system was already able to exchange some packets with the router.

You can test re-triggering the DHCP exchange by breaking and re-making the connection.[*] Of course if the problem keeps coming back again «randomly», doing this does not solve the underlying problem, and you might want to investigate the connection while it is still broken.

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([*] Apple wrote an optimization which can do the DHCP exchange after an exchange of specific ARP packets. Maybe there are new quirks with this, but I have not seen it used on Linux yet.)

It is common to see this error with a connection using DHCP and WiFi, when the wireless signal is lost at some point. (And you catch it before the wireless layer had given up entirely. I’m not sure why I’ve seen that so many times, perhaps I was observing buggy or badly written systems). But eth1 is not a WiFi connection.

I believe that DHCP for IPv4 operates without requiring any ARP. At least in the initial DHCP exchange.

Remaining possibilities

From the facts in the initial version of your question I struggled to think of any individual scenario which is particularly common. (Including my implicit assumptions. It’s unlikely that someone would post this question without trying to plug their computer in to an operational router).

  • The network you’re connected to has no device with the address 192.168.0.1 . If that’s what gave you a DHCP address, then it was removed from the network. Unplugged, or just died.
  • You configured eth1 manually AND one of
    • you’re not using NetworkManager in Ubuntu Desktop, and
      • you don’t actually have an ethernet link detected (check ethtool ).
      • Or you have an ethernet link detected, but the switch requires you to provide a password or other authentication using 802.1X.
      • Or you have an ethernet link detected, but you’re required to register your computer’s MAC address with the network administrator.

      Источник

      «Destination Host Unreachable» and ssh » No route to host»

      На центосе стоит 2 сетевые карты с этими айпи. И нету подключения к интернету.

      При попытке пинга с Убунты локальной машины центос пишет

      Чего? Ты с локальной машины с убунтой пингуешь сам себя и тебе отвечает центос?

      Я с Убунты(192.168.8.101) пытаюсь пинговать центос(192.168.100.166 и 192.168.8.1) На центосе установлены 2 сетевые карты с такими айпи. К 166 подключен кабель от глобальной сетки, а со второй карты идет кабель в роутер и от роутера второй кабель идет в убунту.

      Не судите, но тут думаю есть проблема.

      route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.8.0 0.0.0.0 255.255.255.0 U 100 0 0 enp2s1 192.168.8.1 192.168.100.166 255.255.255.255 UGH 0 0 0 enp2s5 192.168.8.101 192.168.100.166 255.255.255.255 UGH 0 0 0 enp2s5 192.168.100.0 0.0.0.0 255.255.255.0 U 100 0 0 enp2s5 192.168.100.166 192.168.100.254 255.255.255.255 UGH 0 0 0 enp2s5

      Ну так у Вас просто сеть не работает.

      Начинать надо сначала — приведите список и параметры сетевых интерфейсов на локальной машине (команда ifconfig), а также таблицу маршрутизации (команда ip route).

      Ну и проверьте, есть ли сеть физически (в логах dmesg должны быть строчки, что сетевые интерфейсы подняты).

      Это с какой машины таблица маршрутизации?

      ifconfig enp2s5 Link encap:Ethernet HWaddr 00:16:e6:66:3d:f2 inet addr:192.168.8.101 Bcast:192.168.8.255 Mask:255.255.255.0 inet6 addr: fe80::9d31:3207:5516:4f24/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:21420 errors:0 dropped:1 overruns:0 frame:0 TX packets:12467 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:8616229 (8.6 MB) TX bytes:1984494 (1.9 MB) Interrupt:21 lo Link encap:Локальная петля (Loopback) inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:2153 errors:0 dropped:0 overruns:0 frame:0 TX packets:2153 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:300690 (300.6 KB) TX bytes:300690 (300.6 KB) ip route default via 192.168.8.1 dev enp2s5 proto static metric 100 169.254.0.0/16 dev enp2s5 scope link metric 1000 192.168.8.0/24 dev enp2s5 proto kernel scope link src 192.168.8.101 metric 100 
      ifconfig enp2s1: flags=4163 mtu 1500 inet 192.168.8.1 netmask 255.255.255.0 broadcast 192.168.8.255 ether 00:1e:58:2b:f3:d8 txqueuelen 1000 (Ethernet) RX packets 10877 bytes 1691073 (1.6 MiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 35 bytes 3226 (3.1 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 enp2s5: flags=4163 mtu 1500 inet 192.168.100.166 netmask 255.255.255.0 broadcast 192.168.100.255 inet6 fe80::216:e6ff:fe66:3830 prefixlen 64 scopeid 0x20 ether 00:16:e6:66:38:30 txqueuelen 1000 (Ethernet) RX packets 21222 bytes 3227539 (3.0 MiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 7336 bytes 1019089 (995.2 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 21 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1 (Local Loopback) RX packets 8204 bytes 1397066 (1.3 MiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 8204 bytes 1397066 (1.3 MiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ip route 192.168.8.0/24 dev enp2s1 proto kernel scope link src 192.168.8.1 metric 100 192.168.8.1 via 192.168.100.166 dev enp2s5 scope link 192.168.8.101 via 192.168.100.166 dev enp2s5 scope link 192.168.100.0/24 dev enp2s5 proto kernel scope link src 192.168.100.166 metric 100 192.168.100.166 via 192.168.100.254 dev enp2s5

      Источник

      Destination Host Unreachable

      I am using Linux laptop and try to ping a Win10 laptop. I ping myself (Linux system) and google.com, both works, which means the IP connection to router and DNS have no problem. But I still got ‘Destination Host Unreachable’ error. Please enlighten. Thank you.

      root@imx8mnlego:~# ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:22 errors:0 dropped:0 overruns:0 frame:0 TX packets:22 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2156 (2.1 KiB) TX bytes:2156 (2.1 KiB) wlan0 Link encap:Ethernet HWaddr 3C:E1:A1:E0:00:80 inet addr:192.168.0.128 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::3ee1:a1ff:fee0:80/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1894 errors:0 dropped:0 overruns:0 frame:0 TX packets:9943 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:3000 RX bytes:91940 (89.7 KiB) TX bytes:2469289 (2.3 MiB) root@imx8mnlego:~# ping 192.168.0.128 PING 192.168.0.128 (192.168.0.128) 56(84) bytes of data. 64 bytes from 192.168.0.128: icmp_seq=1 ttl=64 time=0.109 ms 64 bytes from 192.168.0.128: icmp_seq=2 ttl=64 time=0.122 ms 64 bytes from 192.168.0.128: icmp_seq=3 ttl=64 time=0.122 ms ^C --- 192.168.0.128 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2031ms rtt min/avg/max/mdev = 0.109/0.117/0.122/0.013 ms root@imx8mnlego:~# ping google.com PING google.com (216.58.194.206) 56(84) bytes of data. 64 bytes from sfo03s01-in-f14.1e100.net (216.58.194.206): icmp_seq=1 ttl=118 time=15.1 ms 64 bytes from sfo03s01-in-f14.1e100.net (216.58.194.206): icmp_seq=2 ttl=118 time=18.2 ms 64 bytes from sfo03s01-in-f14.1e100.net (216.58.194.206): icmp_seq=3 ttl=118 time=19.3 ms ^C --- google.com ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2003ms rtt min/avg/max/mdev = 15.101/17.579/19.375/1.810 ms root@imx8mnlego:~#

      Источник

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