2

I have a home network 192.168.0.x from which I am posting this message, on this network I have a CentOS7 host 192.168.0.3 which is running a DNS server for the network.

I can ssh into 192.168.0.3 I can do nslookup to get the IP addresses of remote machines, but I can not ping my router.

[root@san ~]# ping -c3 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.

--- 192.168.0.1 ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 1999ms

Here is what arp reports

[root@san ~]# arp
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.0.8              ether   b8:8d:12:20:36:6c   C                     eno1
192.168.0.13             ether   c0:3f:d5:63:4e:1a   C                     eno1
192.168.0.10             ether   c0:3f:d5:63:52:06   C                     eno1
192.168.0.11             ether   c0:3f:d5:61:e8:54   C                     eno1
192.168.0.7              ether   00:50:56:61:2b:75   C                     eno1
192.168.0.12             ether   c0:3f:d5:63:19:71   C                     eno1
192.168.0.1              ether   c0:a0:bb:f8:1f:d4   C                     eno1

I can ping other machines on the network

[root@san ~]# ping -c3 192.168.0.13
PING 192.168.0.13 (192.168.0.13) 56(84) bytes of data.
64 bytes from 192.168.0.13: icmp_seq=1 ttl=64 time=0.248 ms
64 bytes from 192.168.0.13: icmp_seq=2 ttl=64 time=0.377 ms
64 bytes from 192.168.0.13: icmp_seq=3 ttl=64 time=0.366 ms

--- 192.168.0.13 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.248/0.330/0.377/0.060 ms

Here is what route prints

[root@san ~]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         192.168.0.1     0.0.0.0         UG    1024   0        0 eno1
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eno1
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 enp0s20u4

here is the ifconfig output

[root@san ~]# ifconfig
eno1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.3  netmask 255.255.255.0  broadcast 192.168.0.255
        inet6 fe80::c23f:d5ff:fe63:d1dd  prefixlen 64  scopeid 0x20<link>
        ether c0:3f:d5:63:d1:dd  txqueuelen 1000  (Ethernet)
        RX packets 6513  bytes 1321730 (1.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 15991  bytes 18326750 (17.4 MiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 20  memory 0xf7c00000-f7c20000  

enp0s20u4: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.0.4  netmask 255.255.255.0  broadcast 192.168.0.255
        inet6 fe80::224:9bff:fe0b:ddf2  prefixlen 64  scopeid 0x20<link>
        ether 00:24:9b:0b:dd:f2  txqueuelen 1000  (Ethernet)
        RX packets 469  bytes 36166 (35.3 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 21  bytes 4155 (4.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 0  (Local Loopback)
        RX packets 2122  bytes 642922 (627.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 2122  bytes 642922 (627.8 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Trying to ping google.com also fails even though the name resolution works.

[root@san ~]# ping -c3 google.com
PING google.com (74.125.226.134) 56(84) bytes of data.

--- google.com ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 1999ms

The router can be pinged from other machines on the network output below is from my mac book pro 192.168.0.8

ping -c3 192.168.0.1
PING 192.168.0.1 (192.168.0.1): 56 data bytes
64 bytes from 192.168.0.1: icmp_seq=0 ttl=64 time=1.794 ms
64 bytes from 192.168.0.1: icmp_seq=1 ttl=64 time=2.000 ms
64 bytes from 192.168.0.1: icmp_seq=2 ttl=64 time=1.986 ms

--- 192.168.0.1 ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 1.794/1.927/2.000/0.094 ms

The router in my network is a D-Link DIR-850L and I have it configured to point at 192.168.0.3 as the DNS server for 192.168.0.x network. I also have the DNS server on 192.168.0.3 configured to forward to the google DNS servers 8.8.8.8.

Why can't I ping 192.168.0.1 from 192.168.0.3 even though 192.168.0.3 is the primary DNS server I am using to post this question from my mac 192.168.0.8 which can browse anywhere on the net going through 192.168.0.3 as the DNS but when I am logged into 192.168.0.3 I can't ping 192.168.0.1 and can't go anywhere on the internet?

  • you router might blocking ping request. are you able to ping from 192.168.0.13? – Raza Aug 28 '14 at 4:16
  • 1
    @ams your router is configured to block icmp packets to itself and any traffic going through it, which is why you cant ping. – beginer Aug 28 '14 at 4:40
  • Is that router the D-Link DIR-850L (while searching DIRL-850, Google insists on making that Girl-850)? – Anthon Aug 28 '14 at 6:17
  • @Anthon you are correct about the router being a D-Link DIR-850L – ams Aug 28 '14 at 11:54
  • 1
    @ams are you able to telnet from 192.168.0.3 to 0.1 on port 22 ? Also try telnet google.com 80 and telnet 8.8.8.8 53 from 0.3. Also please post the blocking configurations if any on your router. – beginer Aug 28 '14 at 13:24
1

I'm in doubt about 10.132.168.0.3's routing table:

default         192.168.0.1     0.0.0.0         UG    1024   0        0 eno1
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eno1
192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 enp0s20u4

If host is not a router I prefer that routing table has only two rows in exactly this order:

192.168.0.0     0.0.0.0         255.255.255.0   U     0      0        0 eno1
default         192.168.0.1     0.0.0.0         UG    1024   0        0 eno1

Just try to remove old and create new routes.

  • the machine has two network cards en01 and enp0o20u4 I think this is why there are three lines. enp0s20u4 is a usb ethernet adapter when I unplug it the third line is removed but I still have the same problem. – ams Aug 28 '14 at 11:56
0

It turned out that my DIR-850L was to blame, I have replaced it with a Asus RT-AC66R and everything is working correctly as expected now.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.