Do you want it to work when the interface is up? What I was trying to say is that with most hardware it will work when the interface is up or down, or it will not work when the interface is up or down. You can't do what I think you want.
-----Original Message----- From: Linux on 390 Port [mailto:[EMAIL PROTECTED] Behalf Of John Summerfield Sent: Friday, September 12, 2008 6:10 PM To: LINUX-390@VM.MARIST.EDU Subject: Re: 127.0.0.2 in /etc/hosts? Fargusson.Alan wrote: > The problem I eluded to is that some network cards and hubs don't send and > receive at the same time, so if you send a packet to your own IP address you > don't see it come back. That means that you won't be able to access machine > x from machine x using the IP address. The loopback interface always works, > which is why most systems either use a special route, or has a /etc/host > entry to a 127.* address. As I said before, I don't want my external IP address/hostname apparently working when the interface is down. > > I am going to guess that virtual networks on z/VM will always act as if the > send and receive at the same time, so this isn't going to be a problem under > z/VM. The real network cards for zSeries may even handle this case specially. > > -----Original Message----- > From: Linux on 390 Port [mailto:[EMAIL PROTECTED] Behalf Of > John Summerfield > Sent: Friday, September 12, 2008 9:35 AM > To: LINUX-390@VM.MARIST.EDU > Subject: Re: 127.0.0.2 in /etc/hosts? > > > Fargusson.Alan wrote: >> This is a question for Novell, although I think they are changing to conform >> to some new network standard. It isn't just Novell that is changing this. >> I have seen some other Unix and Linux systems doing this as well (although I >> can't remember which one right now). >> >> I just did a netstat -r on SLES 10 SP1 and I didn't see my IP routed to the >> loopback interface. I did a netstat -r on Windows and I did. It may be >> that SP1 fails to access itself on some networks. This may be the reason >> for the change. >> >> I think the issue is that this case has been handled in the routing tables. >> If you do a route command (or a netstat -r) on most systems you will see >> that the IP address of your system is specially routed to the loopback >> interface. The problem is that routing tables can get messed up, and things >> break. Having he hostname specifically 127.* avoids some of these problems. > > I'd never seen that before. However, here's a Leopard: > > gargant:~ root# netstat -rn > Routing tables > > Internet: > Destination Gateway Flags Refs Use Netif Expire > default 192.168.1.252 UGSc 5 2 en1 > 127 127.0.0.1 UCS 0 0 lo0 > 127.0.0.1 127.0.0.1 UH 6 44459 lo0 > 169.254 link#5 UCS 1 0 en1 > 169.254.112.1 0:30:65:2:4:a9 UHLW 0 0 en1 398 > 192.168.1 link#5 UCS 4 0 en1 > 192.168.1.71 0:30:65:2:4:a9 UHLW 0 0 en1 422 > 192.168.1.250 127.0.0.1 UHS 0 0 lo0 > 192.168.1.252 0:d:56:c5:48:30 UHLW 3 67 en1 1168 > > Internet6: > Destination Gateway > Flags Netif Expire > ::1 link#1 > UHL lo0 > fe80::%lo0/64 fe80::1%lo0 > Uc lo0 > fe80::1%lo0 link#1 > UHL lo0 > fe80::%en1/64 link#5 > UC en1 > fe80::203:93ff:fec0:4b18%en1 0:3:93:c0:4b:18 > UHL lo0 > ff01::/32 ::1 > U lo0 > ff02::/32 fe80::1%lo0 > UC lo0 > ff02::/32 link#5 > UC en1 > gargant:~ root# > > > So latest OS X is doing it. > > My Debian/Etch system does not. Whether it's because Debian does not, or > because it has several active interfaces I don't know. > > My sl5/CentOS5 systems do not. > My WBEL4/CentOS4 systems do not. > > I imagine that route would allow one to use the IP address of a down > interface. I'm not sure I'd want that. > > I suspect that having that entry in /etc/hosts would do the same thing, > again I'm not sure I'd want that. > > If a network interface is down, I want it down and obviously not > working. Doing otherwise might hide a problem and prevent its being > discovered in a timely manner, and complicate diagnosis of problems when > it cannot be accessed from outside, but works from the host itself. > > I also wonder what it might do to my firewall rules. > > A problem I do have is connected with my one public IP address. If mo > (soho-grade) ADSL router has it, and I try to access the external IP > address from inside the LAN, the ADSL router gets confused when traffic > arrives _from_ the LAN that is supposed to be going _to_ the LAN. I have > worked around that one by creating a dummy interface (ifconfig dummy0) > on the server. Putting the ADSL router in bridge mode and running pppoe > on the Linux box works too. > > However, I don't think this solution is directed to my problem. > > > > >> >> -----Original Message----- >> From: Linux on 390 Port [mailto:[EMAIL PROTECTED] Behalf Of >> John Summerfield >> Sent: Thursday, September 11, 2008 6:03 PM >> To: LINUX-390@VM.MARIST.EDU >> Subject: Re: 127.0.0.2 in /etc/hosts? >> >> >> Michael MacIsaac wrote: >> >>> I can see how SuSE/Novell can argue that it is a valid value (i.e. >>> "working as designed"), but if it affects important applications such as >>> SAP and DB2, I can see how it might be viewed as a bug by the customer. >> "working as designed" does not preclude a faulty design. >> >> There might be some debate as to where the faulty design(s) exist, but >> _I_ would argue against a design change that breaks stuff. >> >> What problem is Novell trying to fix with this? > > > > -- > > Cheers > John > > -- spambait > [EMAIL PROTECTED] [EMAIL PROTECTED] > -- Advice > http://webfoot.com/advice/email.top.php > http://www.catb.org/~esr/faqs/smart-questions.html > http://support.microsoft.com/kb/555375 > > You cannot reply off-list:-) > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > > __________________________________________________________________________________________________ > > CONFIDENTIALITY NOTICE: This email from the State of California is for the > sole use of the intended recipient and may contain confidential and > privileged information. Any unauthorized review or use, including disclosure > or distribution, is prohibited. If you are not the intended recipient, > please contact the sender and destroy all copies of this email. > -- Cheers John -- spambait [EMAIL PROTECTED] [EMAIL PROTECTED] -- Advice http://webfoot.com/advice/email.top.php http://www.catb.org/~esr/faqs/smart-questions.html http://support.microsoft.com/kb/555375 You cannot reply off-list:-) ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
