On Wed, December 23, 2015 8:06 am, Meikel wrote:
> Hi folks,
>
> I have a server at Soyoustart.com (which is a brand of OVH). I run
> CentOS 6.7 and have problems with network configuration.
>
> I want to add a second public ip (failover ip) to the server and did
> follow the instructions in the CentOS-section of
> http://hilfe.ovh.de/AdministrationIpAliasHinzufuegen
>
> After executing the required steps I'm not able to reach the host via
> the second ip from an external host. I tried it with ping and with ssh
> commands.
>
> Here the content of the config files (I anonymized the server ip with
> xx.xx.xx.xx and the failover ip with yy.yy.yy.yy):
>
> $ cat /etc/sysconfig/network
> NETWORKING=yes
> HOSTNAME=<name-of-my-host>
> NOZEROCONF=true
> GATEWAY=xx.xx.xx.254
>
> $ cat /etc/sysconfig/network-scripts/ifcfg-eth0
> DEVICE=eth0
> BOOTPROTO=static
> IPADDR=xx.xx.xx.xx
> NETMASK=255.255.255.0
> ONBOOT=yes
> GATEWAY=xx.xx.xx.254
>
> $ cat /etc/sysconfig/network-scripts/ifcfg-eth0:0
> DEVICE=eth0:0
> BOOTPROTO=static
> IPADDR=yy.yy.yy.yy
> NETMASK=255.255.255.255
> ONBOOT=yes
If I understand IP networking correctly, you only can have "aliases" of
the interface appear on the _same_ network segment (I'm tempted to say
same class C network) as the main IP of interface, say you have:
DEVICE=eth0
IPADDR=x.y.z.w
NETMASK=255.255.255.0
GATEWAY=x.y.z.254
Then with the restriction I mentioned you can have alias:
DEVICE=eth0:0
IPADDR=x.y.z.a
NETMASK=255.255.255.255
Note that "x.y.z." part is the same in both IPs.
Somebody may correct me if I'm wrong.
Valeri
>
> When I restart the network I get a message (two times) saying "RTNETLINK
> answers: Operation not supported".
>
> $ service network restart
> Schnittstelle eth0 beenden: [ OK ]
> Loopback-Schnittstelle beenden: [ OK ]
> Loopback-Schnittstelle hochfahren: [ OK ]
> Schnittstelle eth0 hochfahren: Determining if ip address xx.xx.xx.xx is
> already in use for device eth0...
> RTNETLINK answers: Operation not supported
> RTNETLINK answers: Operation not supported
> [ OK ]
>
> I can see two interfaces eth0 and eth0:0
>
> $ LANG="" ifconfig
> eth0 Link encap:Ethernet HWaddr ..:..:..:..:..:..
> inet addr:xx.xx.xx.xx Bcast:xx.xx.xx.255 Mask:255.255.255.0
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:11122 errors:0 dropped:0 overruns:0 frame:0
> TX packets:14371 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:1000
> RX bytes:1362900 (1.2 MiB) TX bytes:3462327 (3.3 MiB)
> Interrupt:20 Memory:fe500000-fe520000
>
> eth0:0 Link encap:Ethernet HWaddr ..:..:..:..:..:..
> inet addr:yy.yy.yy.yy Bcast:yy.yy.yy.yy Mask:255.255.255.255
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> Interrupt:20 Memory:fe500000-fe520000
>
> lo Link encap:Local Loopback
> inet addr:127.0.0.1 Mask:255.0.0.0
> UP LOOPBACK RUNNING MTU:65536 Metric:1
> RX packets:3096 errors:0 dropped:0 overruns:0 frame:0
> TX packets:3096 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:0
> RX bytes:274948 (268.5 KiB) TX bytes:274948 (268.5 KiB)
>
>
> I'm able to reach the host from another host (outside OVH network) via
> xx.xx.xx.xx (I use ping and ssh), but not via yy.yy.yy.yy.
>
> Just to be sure that there isn't an issue with the firewall I did
> "service iptables stop" and ran the "ping" and "ssh" commands again with
> the same result. For ip xx.xx.xx.xx it works, but not for yy.yy.yy.yy.
>
> Not sure if this is important, just in case it matters, some additional
> information:
>
> IPv6 is disabled by kernel parameter "ipv6.disable=1" in /etc/grub.conf
>
> The two mac addresses I see for eth0 and eth0:0 with the "ifconfig"
> command are the same. In the OVH/Soyoustart.com GUI I created a virtual
> mac for the failover ip, I'm not sure if that virtual mac should come
> into play somewhere?
>
> $ uname -a
> Linux <name-of-my-host> 2.6.32-573.12.1.el6.x86_64 #1 SMP Tue Dec 15
> 21:19:08 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
>
> $ LANG="" route
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> xx.xx.xx.0 * 255.255.255.0 U 0 0 0 eth0
> default vss-gw-6k.fr.eu 0.0.0.0 UG 0 0 0 eth0
>
> Why is yy.yy.yy.yy not reachable from outside? What am I doing wrong or
> what can I do to narrow down the problem?
>
> Regards,
>
> Meikel
>
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++++++++++++++++++++++++++++++++++++++++
Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247
++++++++++++++++++++++++++++++++++++++++
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