On 02/24/2017 02:19 AM, Gary Stainburn wrote:
> Here's an odd one for you.
>
> I have a Fedora 19 box - GROUCHO - that is the DNS/DHCP/email/...... server
> for one of my LANs
>
> On there I have a home-grown network status monitor which pings a list of
> IP's
> and monitors the state, reporting anything that goes missing.
>
> The IP address of this host is 10.6.1.1/24
>
> I also have a Centos 7 box - ZEPPO - on the same subnet/VLAN. This box is a
> file/print server.
>
> This box has two IP addresses 10,6.1.3/24 and 10.6.1.101/24
>
> Groucho happily pings Zeppo on the 10.6.1.101 address.
>
> I have now added a USB WiFi dongle to Zeppo and configured it using nmtui.
> This is to put Zeppo onto the WiFi and enable Air Printing from IPads.
>
> All of this works perfectly fine, and no other devices have any issues -
> except groucho.
>
> If the WiFi link is up on Zeppo, Groucho cannot ping it. If the WiFi link is
> down on Zeppo, Groucho can ping it. As I say, the WiFi link state doesn not
> affect any other device, Linux or otherwise.
>
> Neither device have firewalling enabled (for this testing) and both devices
> have very simple routing tables. Even when Groucho cannot ping Zeppo, Zeppo
> can still ping Groucho
>
> ---------------------------------------------------
> [root@zeppo ~]# route -n
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> 0.0.0.0 10.6.1.254 0.0.0.0 UG 100 0 0 enp3s0
> 10.6.1.1 10.6.103.254 255.255.255.255 UGH 600 0 0
> wlp0s26u1u2
> 10.6.1.3 0.0.0.0 255.255.255.255 UH 100 0 0 enp3s0
> 10.6.1.101 0.0.0.0 255.255.255.255 UH 100 0 0 enp3s0
> 10.6.1.254 0.0.0.0 255.255.255.255 UH 100 0 0 enp3s0
> 10.6.103.0 0.0.0.0 255.255.255.0 U 600 0 0
> wlp0s26u1u2
> [root@zeppo ~]# nmcli con up RW54254
> Connection successfully activated (D-Bus active
> path: /org/freedesktop/NetworkManager/ActiveConnection/2)
> [root@zeppo ~]#
>
> ---------------------------------------------------
> [root@groucho ~]# route -n
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> 0.0.0.0 10.6.1.254 0.0.0.0 UG 0 0 0 p4p1
> 10.6.1.0 0.0.0.0 255.255.255.0 U 1 0 0 p4p1
> 169.254.0.0 0.0.0.0 255.255.0.0 U 1002 0 0 p4p1
> [root@groucho ~]# ping zeppo
> PING zeppo.ringways.co.uk (10.6.1.101) 56(84) bytes of data.
> From groucho.ringways.co.uk (10.6.1.1) icmp_seq=1 Destination Host Unreachable
> From groucho.ringways.co.uk (10.6.1.1) icmp_seq=2 Destination Host Unreachable
> From groucho.ringways.co.uk (10.6.1.1) icmp_seq=3 Destination Host Unreachable
> From groucho.ringways.co.uk (10.6.1.1) icmp_seq=4 Destination Host Unreachable
> ^C
> --- zeppo.ringways.co.uk ping statistics ---
> 5 packets transmitted, 0 received, +4 errors, 100% packet loss, time 4002ms
> pipe 4
> [root@groucho ~]#
The most common issue with this sort of thing is ARP and/or route
confusion. You have a machine with two interfaces on the same network.
Try doing this as root on zeppo (the machine with two interfaces):
echo "1" >/proc/sys/net/ipv4/conf/all/arp_ignore
echo "2" >/proc/sys/net/ipv4/conf/all/arp_announce
And try your pings again. If that solves your problem, add these lines
to your /etc/sysctl.conf file:
# needed for two NICs on the same network
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
That will make them effective on a reboot. If that doesn't fix your
issue, reset the values via:
echo "0" >/proc/sys/net/ipv4/conf/all/arp_ignore
echo "0" >/proc/sys/net/ipv4/conf/all/arp_announce
----------------------------------------------------------------------
- Rick Stevens, Systems Engineer, AllDigital ri...@alldigital.com -
- AIM/Skype: therps2 ICQ: 226437340 Yahoo: origrps2 -
- -
- Huked on foniks reely wurked for me! -
----------------------------------------------------------------------
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