Mailing List Archive

Network iface is down but pingable
With Linux 2.2.12 and "ip utility, iproute2-ss990630" I see the following
buggy(?) behaviour:
After I "ifconfig down" or "ip link set iface down" a network interface, the
ip number of that interface is still pingable. If first encountered this with
an ethernet interface but can reproduce it now only with a ISDN PPP interface.
After "ifconfig <iface> down" or "ip link set <iface> down" an "ifconfig"
doesn't see the interface any more and "ip link show" correctly doesn't give
the "UP" flag. But with "ip route list table local" I can still see the route
for the IP number of the downed interface going to said interface. And ping
or other network access works.
I think this is a bug, if the interface is gone, the route should go too. If
this is not a bug maybe somebody can enlighten me on the proper procedure
for taking an interface down.
Jochen
--
Jochen Topf - jochen@remote.org - http://www.remote.org/jochen/
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Re: Network iface is down but pingable [ In reply to ]
On Wed, 6 Oct 1999, Jochen Topf wrote:
> With Linux 2.2.12 and "ip utility, iproute2-ss990630" I see the following
> buggy(?) behaviour:
>
> After I "ifconfig down" or "ip link set iface down" a network interface, the
> ip number of that interface is still pingable. If first encountered this with
> an ethernet interface but can reproduce it now only with a ISDN PPP interface.
>
> After "ifconfig <iface> down" or "ip link set <iface> down" an "ifconfig"
> doesn't see the interface any more and "ip link show" correctly doesn't give
> the "UP" flag. But with "ip route list table local" I can still see the route
> for the IP number of the downed interface going to said interface. And ping
> or other network access works.
>
> I think this is a bug, if the interface is gone, the route should go too. If
> this is not a bug maybe somebody can enlighten me on the proper procedure
> for taking an interface down.
>
Others have thought that this is a bug also. However, it was decided that
it is not a bug although the logic escapes me. A work-around is to
reset the interface address, i.e.,
ifconfig eth0 down
ifconfig eth0 127.0.0.2 netmask 255.0.0.0 broadcast 127.255.255.255
ifconfig eth0 down
That will keep it quiet until somebody fixes the non-bug.
Cheers,
Dick Johnson
**** FILE SYSTEM WAS MODIFIED ****
Penguin : Linux version 2.3.13 on an i686 machine (400.59 BogoMips).
Warning : It's hard to remain at the trailing edge of technology.
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Re: Network iface is down but pingable [ In reply to ]
Richard B. Johnson writes ("Re: Network iface is down but pingable"):
> On Wed, 6 Oct 1999, Jochen Topf wrote:
> > I think this is a bug, if the interface is gone, the route should go too. If
> > this is not a bug maybe somebody can enlighten me on the proper procedure
> > for taking an interface down.
>
> Others have thought that this is a bug also. However, it was decided that
> it is not a bug although the logic escapes me.
From the description, I would say that there is a bug, but it is NOT
that the route isn't removed.
Deleting the route when an interface is taken down is like deleting a
symlink when the target file is deleted. It's extremely frustrating if
you have a non-trivial configuration and all you wanted to do was to
attempt to reset the ethernet controller with rmmod/insmod.
Peter
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Re: Network iface is down but pingable [ In reply to ]
pjb1008@cam.ac.uk (Peter Benie) writes:
> Deleting the route when an interface is taken down is like deleting a
> symlink when the target file is deleted. It's extremely frustrating if
> you have a non-trivial configuration and all you wanted to do was to
> attempt to reset the ethernet controller with rmmod/insmod.
If you rmmod the ethernet driver module, you lose ethxx device, all
its addresses and routes.
--
Krzysztof Halasa
Network Administrator
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Re: Network iface is down but pingable [ In reply to ]
Krzysztof Halasa writes ("Re: Network iface is down but pingable"):
> pjb1008@cam.ac.uk (Peter Benie) writes:
>
> > Deleting the route when an interface is taken down is like deleting a
> > symlink when the target file is deleted. It's extremely frustrating if
> > you have a non-trivial configuration and all you wanted to do was to
> > attempt to reset the ethernet controller with rmmod/insmod.
>
> If you rmmod the ethernet driver module, you lose ethxx device, all
> its addresses and routes.
Then that's anther bug :-(.
Peter
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Re: Network iface is down but pingable [ In reply to ]
pjb1008@cam.ac.uk (Peter Benie) writes:
> > If you rmmod the ethernet driver module, you lose ethxx device, all
> > its addresses and routes.
>
> Then that's anther bug :-(.
Why? You have scripts which can bring it back to life.
--
Krzysztof Halasa
Network Administrator
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Re: Network iface is down but pingable [ In reply to ]
Krzysztof Halasa wrote:
> pjb1008@cam.ac.uk (Peter Benie) writes:
>
> > > If you rmmod the ethernet driver module, you lose ethxx device, all
> > > its addresses and routes.
> >
> > Then that's anther bug :-(.
>
> Why? You have scripts which can bring it back to life.
scripts are NOT the right approach to this. given that you have a network
map laid out and dynamically balanced interfaces, setting an interface
up/down should in no way change the routing paths, only that the route should
be marked inactive or dead.
if i load balance several NICs with a daemon, i'd feel pretty silly (stupid
really) shelling to run a script to bring routes back up.
if i run a heavily trafficked network and have need to switch NICs up/down at
any fast rate, i'd be considered intellectually challenged to use this
approach. consider if i have two hundred routes balanced through three cards
and due to some strangeness, say a stuttering network card, my daemon starts
switching cards every few seconds. running scripts to manage this sounds
like one of the greatest DoS ideas in recent times.
how much cpu does an ioctl(...) take v.s. a system(...)?
the ONLY affect NIC's status change should have on routing is marking routes
dead or alive, NOT flushing them.
the current method, pardon the bluntness, is a m$ way of doing it. knock
down all the dominoes because one of them needs to go down, now set up the
others that should stay up.
scripts have a place. performance and efficiency are not that place.
-d
--
This is Linux Country. On a quiet night, you can hear Windows NT reboot!
Do you remember how to -think- ? Do you remember how to experiment? Linux
__ is an operating system that brings back the fun and adventure in computing.
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Re: Network iface is down but pingable [ In reply to ]
David Ford <david@kalifornia.com> writes:
> if i load balance several NICs with a daemon, i'd feel pretty silly (stupid
> really) shelling to run a script to bring routes back up.
You can ask your daemon to add routes for you. I'm not sure if I like the
idea of automatic routes created by "ifconfig up", but using them you
already have a route to your peer/network when the interface is up.
A daemon like mrtd can add default and other routes for you without
any need for slow scripts.
> the ONLY affect NIC's status change should have on routing is marking routes
> dead or alive, NOT flushing them.
>
> the current method, pardon the bluntness, is a m$ way of doing it. knock
> down all the dominoes because one of them needs to go down, now set up the
> others that should stay up.
Not really. You only flush routes associated with the interface in question,
not the whole routing table. I'd be very surprised if I someday realize
that after rmmoding the driver I still have routes using it or even the
actual interface.
OTOH ifconfig up/down and rmmod/insmod are rather administrative tasks,
like adding or removing routes is. Linux doesn't currently have "link/
protocol down" state, but I think only that condition should mark routes
as dead without removing them from the table. That would be nice, BTW.
--
Krzysztof Halasa
Network Administrator
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Re: Network iface is down but pingable [ In reply to ]
--lrZ03NoBR/3+SXJZ
Content-Type: text/plain; charset=iso-8859-1
Content-Transfer-Encoding: quoted-printable
Dec=EDa Jochen Topf:
>=20
> After I "ifconfig down" or "ip link set iface down" a network interface, =
the
> ip number of that interface is still pingable. If first encountered this =
with
> an ethernet interface but can reproduce it now only with a ISDN PPP inter=
face.
Well, I also can create an address with ip address add ( and without alias
support in kernel), could ping the address. Is it a correct behaviur ?. I h=
ave
a device ( I look it with ifconfig -a ) , but the address isn't there.
Saludos
Drizzt
--=20
____________________________________________________________________________
Drizzt Do'Urden Three rings for the Elves Kings under the Sk=
y =20
drizzt.dourden@iname.com Seven for the Dwarf_lords in their =20
http://www.arrakis.es/~terron hall of stone
FIDO 2:345/506.440 Nine for the Mortal Men doomed to die=20
--lrZ03NoBR/3+SXJZ
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Re: Network iface is down but pingable [ In reply to ]
Krzysztof Halasa wrote:
> David Ford <david@kalifornia.com> writes:
>
> > if i load balance several NICs with a daemon, i'd feel pretty silly (stupid
> > really) shelling to run a script to bring routes back up.
>
> You can ask your daemon to add routes for you. I'm not sure if I like the
> idea of automatic routes created by "ifconfig up", but using them you
> already have a route to your peer/network when the interface is up.
> A daemon like mrtd can add default and other routes for you without
> any need for slow scripts.
on some of my machines i have over a dozen non-simplified routes that are built
from a variety of signals. those signals don't necessarily exist again until
some time in the future. in this case, it is silly to continuously save a state
table of the routes so when a NIC swap occurs i have correct information. ip
link set up/down only brings up a route specific to the scope of the interface,
none other.
the concept of having a daemon add routes a split second after routes are deleted
by the kernel is rather silly. just leave the routes there and mark them dead.
it's less work for the kernel and less work for userland.
> > the ONLY affect NIC's status change should have on routing is marking routes
> > dead or alive, NOT flushing them.
> >
> > the current method, pardon the bluntness, is a m$ way of doing it. knock
> > down all the dominoes because one of them needs to go down, now set up the
> > others that should stay up.
>
> Not really. You only flush routes associated with the interface in question,
> not the whole routing table. I'd be very surprised if I someday realize
> that after rmmoding the driver I still have routes using it or even the
> actual interface.
yes really, all the routing depends on interfaces dependant upon those
interfaces. and for the second sentence, routes marked dead are not usable.
routing stops over that route but the state information remains so you only need
mark it active again.
> OTOH ifconfig up/down and rmmod/insmod are rather administrative tasks,
> like adding or removing routes is. Linux doesn't currently have "link/
> protocol down" state, but I think only that condition should mark routes
> as dead without removing them from the table. That would be nice, BTW.
no, ip link set up/down rm/insmod can be human admin tasks and can well be
automated tasks. hmm, i do suggest you delve into the current NET4
functionality. there's a ton more to it than the simplistic "ifconfig" and
"route" i think you're currently familiar with. :)
-d
--
This is Linux Country. On a quiet night, you can hear Windows NT reboot!
Do you remember how to -think- ? Do you remember how to experiment? Linux
__ is an operating system that brings back the fun and adventure in computing.
\/ for linux-kernel: please read linux/Documentation/* before posting problems
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Re: Network iface is down but pingable [ In reply to ]
Drizzt wrote:
> Well, I also can create an address with ip address add ( and without alias
> support in kernel), could ping the address. Is it a correct behaviur ?. I have
> a device ( I look it with ifconfig -a ) , but the address isn't there.
ifconfig isn't capable of displaying all the information on interfaces. yes, this
is correct behavior.
ip a s will give you all the addresses on all interfaces.
-d
--
This is Linux Country. On a quiet night, you can hear Windows NT reboot!
Do you remember how to -think- ? Do you remember how to experiment? Linux
__ is an operating system that brings back the fun and adventure in computing.
\/ for linux-kernel: please read linux/Documentation/* before posting problems
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