1. IP aliasing Problem
hi;
I just stumbled over this problem while migrating from RH5.2 to RH6:
What we have :
Interface private IP real IP (translated by
cisco (NAT)
-----------------------------------------------------
eth0 192.168.1.125 <-------> a.b.c.d1
eth0:1 192.168.1.126 <-------> a.b.c.d2
eth0:2 192.168.1. 127 <-------> a.b.c.d3
eth0:3 192.168.1.128 <-------> a.b.c.d4
stuff added to rc.local :
# routing
route add default gw cisco-gw
route add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.1.2
# virtual Interface(s)
ifconfig eth0:1 192.168.1.126 netmask 255.255.255.0 up
ifconfig eth0:2 192.168.1.127 netmask 255.255.255.0 up
ifconfig eth0:3 192.168.1.128 netmask 255.255.255.0 up
My machine has one physical Interface (one IP) with 3 virtual IPs like
this {eth0 eth0:1 eth0:2 eth0:3} bound to the same
Interface. We have a cisco Router which translates (NATs) the private
IPs bound to the eth's to real IPs. Default Gateway is the cisco
(cisco-gw). With RH5.2 this works as expected - _all_ 4 adresses are
global visible (Internet) via the NAT translations - i.e i can reach
each a.b.c.d?.
Now we moved to a SMP machine with RH6 (default Kernel Version
re-compiled to match processor etc.) and absolut
identical Configuration (copied from old machines rc.local to new ones
!) and ended up
with only the first adress 'global' visible (the eth0 !) and all 3
virtual adresses local visible (private LAN) only.
This means i can connect to all private IPs of the eth:x Interfaces
(192.168.1.x) but get no reply to the mapped ones
(a.b.c.d?). Can someone please explain why this doesn't work anymore and
what to do. To me it seems the default
gateway bound to the virtual IPs is broken or the configuration
procedure has changed.
PS Due to this 'bug'/whatever we moved back to the old machine until
this problem is resolved (the old machine works
fine as ever - so this is definitly a Linux problem !)
thanks in advance
hb
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UNIX SysAdmin - BCI GmbH
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