[GLLUG] IP Aliases and routing

Subba Rao sailorn@attglobal.net
Mon, 4 Nov 2002 14:8:14 -0500

Thank you for replying.

I am not using any NAT or IPTABLES/IPCHAINS.  The system is left wide open.
It is actually a test server, since we do not have several boxes to setup.  The aliased
addresses are on different subnets. ( etc) All of them
have a 24 bit subnet mask.  The actual IP address of the interface (eth0) is
The syslog server is (which is an aliased address).

The gateway to this Linux can ping, telnet to any of the addresses assigned to the Linux eth0.
Syslog does not get logged.

Do I need to add a route on the Linux server?  Are there any special syslog configuration issues
to get to accept syslog?

Best regards.				 
Subba Rao

======= At 2002-11-04, 07:55:00 you wrote: =======

>I have a similar box, but with multiple NICs rather than aliases, and I
>use the NAT functions of IPTABLES to route my packets to their
>appropriate destination IPs.  As long as the OS doesn't know the
>difference between aliases and physical interfaces, I'm pretty sure nat
>would work for you too.
>Regarding the server packages, most should have a configuration option
>for binding to a specific IP.  I know at least Apache, OpenSSH, and most
>FTP servers can bind themselves to a specific IP address or listen on
>all addresses by default.
>--Brad Fears
>On Sat, 2002-11-02 at 10:48, Subba Rao wrote:
>> Hello,
>> We have a Linux PC which has only one NIC with several IP Aliased
>> addresses.  The aliased addresses are on different subnets.  Th Linux PC
>> is pretty much behaving like a router.  I can ping all the address from the
>> actual gateway that is connected to the Linux PC.  All the typical servers
>> (FTP, Telnet, SMTP, HTTP, Syslog etc.) are running on this Linux PC.
>> One of the aliased addresses (S.S.S.S) is serving as the syslog server for the gateway.
>> When I watch the traffic using tcpdump,  the syslog packet makes it to the Linux PC but returned
>> back (or dropped) because it cannot route it to S.S.S.S.
>> I have 2 questions for this setup.
>> 1. How do I route the packets on the Linux PC to it's alias address S.S.S.S?
>> 2. Do the Linux servers (FTP,Telnet,SMTP,Syslog.....etc) bind to the actual interface address?
>>     Or they attached to the IP Aliases as well?
>> Thank you in advance for any help.
>> Subba Rao
>> sailorn@attglobal.net
>> 2002-11-02

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