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Date:      Tue, 21 Dec 1999 11:26:26 +0300 (MSK)
From:      Dmitry Valdov <dv@dv.ru>
To:        "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>
Cc:        freebsd-stable@freebsd.org
Subject:   Re: alias ip addresses not pingable
Message-ID:  <Pine.BSF.3.95q.991221111246.24276D-100000@xkis.kis.ru>
In-Reply-To: <199912202308.PAA44335@gndrsh.dnsmgr.net>

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Hi!

btw, I've seen the same problem. I think it doesn't depend on netmask. 
I'll try to explain:
ifconfig doesn't add route for new alias to loopback if You ping new IP
address before adding it as alias. For example:
1. We are going to add IP 1.2.3.4 as alias to ed0
2. ping 1.2.3.4 (before adding) - from the same host (!)
3. ifconfig ed0 1.2.3.4 255.255.255.255 alias
Result: 
ping from other host - OK
ping from localhost - not OK
4. route add 1.2.3.4 127.0.0.1
ping from localhost - OK.

If You skip step 2 in this example, You'll not need to route add 1.2.3.4 to
loopback - it adds automaticly.



So, in his example when he tests it after boot it "makes" step 2. as in my
example. 

Why?

Sorry for my english. I think, You understood.

Example:

comin# ping 195.98.32.140
PING 195.98.32.140 (195.98.32.140): 56 data bytes
^C
--- 195.98.32.140 ping statistics ---
4 packets transmitted, 0 packets received, 100% packet loss   
comin# ifconfig fxp0 inet 195.98.32.140 netmask 255.255.255.255 alias
comin# ping 195.98.32.140
PING 195.98.32.140 (195.98.32.140): 56 data bytes
ping: sendto: Host is down
ping: sendto: Host is down
ping: sendto: Host is down
^C
--- 195.98.32.140 ping statistics ---
5 packets transmitted, 0 packets received, 100% packet loss         

and:

comin# ifconfig fxp0 inet 195.98.32.141 netmask 255.255.255.255 alias
comin# ping 195.98.32.141
PING 195.98.32.141 (195.98.32.141): 56 data bytes
64 bytes from 195.98.32.141: icmp_seq=0 ttl=255 time=0.084 ms
64 bytes from 195.98.32.141: icmp_seq=1 ttl=255 time=0.051 ms
^C
--- 195.98.32.141 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.051/0.068/0.084/0.016 ms           


Dmitry.

On Mon, 20 Dec 1999, Rodney W. Grimes wrote:

> Date: Mon, 20 Dec 1999 15:08:31 -0800 (PST)
> From: "Rodney W. Grimes" <freebsd@gndrsh.dnsmgr.net>
> To: Randy Bush <randy@psg.com>
> Cc: eddy@isi.edu, FreeBSD Stable <freebsd-stable@FreeBSD.ORG>
> Subject: Re: alias ip addresses not pingable
> 
> > >> aliases should have a netmask of 255.255.255.255, as seen in ifconfig(8)
> > > why?  i regularly use aliases with masks smaller than /32, on a 3.1
> > > system e.g:
> > 
> > well, it turned out that
> > 
> > if i
> >   boot with the alias netmask of 255.255.255.0
> > it does not work
> >   delete the alias
> >   ifconfig the alias with a /32
> > it still does not work
> > 
> > but if i boot with a /32 alias, it works!
> 
> Take a look at netstat -rn in the 2 different situations you describe
> above.  Your probably getting an error during the boot with alias /24
> that has to do with the fact it can't add the route to the address as
> the route already exists.
> 



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