IP-aliases, sporadically changing src address for outbound traffic
Hello,
I have a debian/sarge web- and mailserver (kernel 2.6.8-2-386) with one
interface and 3 IP-aliases on the same subnet (see
/etc/network/interfaces below).
Today the default src address for outbound connections seems to have
changed from .213 to .212 and back for no reason. I noticed this because
one php-script connects to a webservice that is configured to accept
connection from .213 only mailed a warning and postfix sending this
warning used .212. I have mails from this server an hour before and
after this warning that use .213 and I cannot reproduce the change with
netcat etc. -- it's always .213.
Then I found four older mails -- using .212. Funny enough the connection
to the webservice works flawlessly for several weeks and I never found
any of the other two IPs (.6 and .178).
I've had minor problems with IP-aliases before -- but only in the way
that adding an alias to the end of /etc/network/interfaces changes the
default outgoing address to the new alias-IP. But then it was a
permanent change (at least I didn't notice any further changes) and you
could permanently change it back with:
ip route add ... dev eth0 src ...
That was a bit annoying but not a real problem.
Now it seems to happen "somtimes" and there is not the slightest trace
of anything suspicious in /var/log/messages. Plus the server is not
loaded at all.
Now I'm a bit puzzled if
a) this is normal/known
b) ip route ... src ... will fix it (hard to test)
Thanks in advance,
Henrik
--- 8< /etc/network/interfaces ---
auto lo eth0 eth0:0 eth0:1 eth0:2
iface lo inet loopback
iface eth0 inet static
address xxx.yyy.zzz.6
netmask 255.255.255.0
gateway xxx.yyy.zzz.1
iface eth0:0 inet static
address xxx.yyy.zzz.178
netmask 255.255.255.0
gateway xxx.yyy.zzz.1
iface eth0:1 inet static
address xxx.yyy.zzz.212
netmask 255.255.255.0
gateway xxx.yyy.zzz.1
iface eth0:2 inet static
address xxx.yyy.zzz.213
netmask 255.255.255.0
gateway xxx.yyy.zzz.1
--- >8 ---
--- 8< ifconfig ---
eth0 Link encap:Ethernet HWaddr 00:0C:76:62:02:A0
inet addr:xxx.yyy.zzz.6 Bcast:xxx.yyy.zzz.255
Mask:255.255.255.0
inet6 addr: fe80::20c:76ff:fe62:2a0/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:101356798 errors:0 dropped:0 overruns:0 frame:0
TX packets:1623084 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1961659835 (1.8 GiB) TX bytes:1032623017 (984.7 MiB)
eth0:0 Link encap:Ethernet HWaddr 00:0C:76:62:02:A0
inet addr:xxx.yyy.zzz.178 Bcast:xxx.yyy.zzz.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth0:1 Link encap:Ethernet HWaddr 00:0C:76:62:02:A0
inet addr:xxx.yyy.zzz.212 Bcast:xxx.yyy.zzz.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth0:2 Link encap:Ethernet HWaddr 00:0C:76:62:02:A0
inet addr:xxx.yyy.zzz.213 Bcast:xxx.yyy.zzz.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
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:16436 Metric:1
RX packets:63385 errors:0 dropped:0 overruns:0 frame:0
TX packets:63385 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:5385623 (5.1 MiB) TX bytes:5385623 (5.1 MiB)
--- >8 ---
--
Henrik Heil, zweipol Coy & Heil GbR
http://www.zweipol.net/
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