Date: Thu, 21 Feb 2008 12:07:08 +0000 From: "Siraj Shaikh" <siraj.shaikh@gmail.com> To: "Olivier Nicole" <on@cs.ait.ac.th> Cc: freebsd-questions@freebsd.org Subject: Re: IP Aliasing Message-ID: <3b2ddd940802210407j7b83059duabadeccaec53a26c@mail.gmail.com> In-Reply-To: <200801290234.m0T2YtLn074403@banyan.cs.ait.ac.th> References: <3b2ddd940801280627m6d747cd1g27682bcd9e50ceb7@mail.gmail.com> <200801290234.m0T2YtLn074403@banyan.cs.ait.ac.th>
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On 29/01/2008, Olivier Nicole <on@cs.ait.ac.th> wrote: > > 1) is there an upper limit to configuring a number of alias addresses? > > I have a machine with 200+ IP without any problem. > > > 2) if an interface is configured with an alias address, then what > > address is shown on the traffic leaving this interface? So, for > > example, if I were to ping this machine on its primary address, I > > expect to get a response from the primary address of the interface. > > What happens if I ping an alias address, would I get a response from > > By default exiting traffic is using the primary address (the one > defined with no keyword alias in the ifconfig). I think there is a way > to choose the exiting IP. > > When a paket is responding, it use the same IP that was used in the > query (else any firewall would be confused in the way). > > > > 3) In the above scenario, all traffic leaving the interface > > (regardless of the source IP on it) will have the same MAC address > > (the one of the interface) - is that right? > > > Right except maybe some NIC that allow several MAC addresses? That > could be used in hi availability? > > > > 4) Does anyone know if there are there any other network > > characteristics or behaviour by which we can distinguish a machine > > having more than one IP address (primary plus alias) configued on one > > of its interface? > > > Once you cross a router, you don't see the MAC of the machine anymore, > MAC is local to your LAN anyway. > > Olivier > > > One last thing I wanted to know (sorry to email after a long delay), in order for me to add aliases that I want to remain configured on the machine at every boot, I can simply add, for exmaple, the following lines to the rc.conf file? ifconfig_ed0_alias0="inet 127.0.0.251 netmask 0xffffffff" ifconfig_ed0_alias1="inet 127.0.0.252 netmask 0xffffffff" ifconfig_ed0_alias2="inet 127.0.0.253 netmask 0xffffffff" Just want to know, as I want to configure about 253 addresses as an alias on a single machine (along with the primary address, this will be 254 address, a whole C-class subnet) - and would like these entries to hold when I boot. Also, is there any shortcut to adding a range of net/host address or would I have to add a line for each address? Thanks
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