[LARTC] Policy routing missing default table?

[LARTC] Policy routing missing default table?

[Adrian Chung]

Hi all, this might have been covered, although going over the archives
at mailman.ds9a.nl, I haven't been able to find it:

I seem to be missing the default table, even though I've got a local
and main table:

[root@wolverine net]# ip rule
0:      from all lookup local
32766:  from all lookup main
32767:  from all lookup 253

Instead, I've got a '253' table...

'wolverine' is a multihomed machine with addresses on the following
networks:

64.26.132.192/26
192.168.8.0/24
192.62.100.0/24

It has a default route on the 64.26.132.192 network, and also routes
to 192.168.8.2 which has a cable modem attached.

What I want to do is have all traffic from 192.62.100.0/24 routed
through a default gateway of 192.168.8.2 instead of wolverine's
default gateway.  I've accomplished this easily by creating a new
table '1' and rule, the table being created before the 'main' table.

The problem is, with this setup, all traffic for the 64.26.132.192/26
network from 192.62.100.0/24 is also routed through 192.168.8.2.

I got around this by adding an explicit rule to route via
64.26.132.193 for anything on 64.26.132.192/26 into table 1.

I was under the impression that my 3 main tables should have been
'local', 'main', and 'default'.  'main' would contain routes to adjacent
networks, and 'default' would contain default routes.  So I could have
solved my problem by just creating a table with precidence in between
main and default, and changed the default gateway for 192.62.100.0/24
without changing network routes too.

Does this make sense?  And if so, does anyone know why I have a table
'253' with nothing in it, and no 'default'?

I'm running iproute2-2.2.4-now-ss001007.tar.gz from
ftp://ftp.inr.ac.ru, with kernel 2.4.5.

My userland utilities, like ifconfig, ifup, etc are from RH6.2ish.
Would they make a difference?

Thanks!

--
Adrian Chung (adrian at enfusion-group dot com)
http://www.enfusion-group.com/~adrian
GPG Fingerprint: C620 C8EA 86BA 79CC 384C E7BE A10C 353B 919D 1A17
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Re: [LARTC] Policy routing missing default table?

[Juri Haberland]

Adrian Chung wrote:
> 
> Hi all, this might have been covered, although going over the archives
> at mailman.ds9a.nl, I haven't been able to find it:
> 
> I seem to be missing the default table, even though I've got a local
> and main table:
> 
> [root@wolverine net]# ip rule
> 0:      from all lookup local
> 32766:  from all lookup main
> 32767:  from all lookup 253
> 
> Instead, I've got a '253' table...

[--snip--]

> I was under the impression that my 3 main tables should have been
> 'local', 'main', and 'default'.  'main' would contain routes to adjacent
> networks, and 'default' would contain default routes.  So I could have
> solved my problem by just creating a table with precidence in between
> main and default, and changed the default gateway for 192.62.100.0/24
> without changing network routes too.

Well, according to the "Linux 2.4 Advanced Routing HOWTO" the default
table (or 253) should be empty and the default route should be in
'main'.

> Does this make sense?  And if so, does anyone know why I have a table
> '253' with nothing in it, and no 'default'?

Actually, I don't know why there isn't a default table but one named
'253'. I have the same here on a RedHat 7.1 system running kernel 2.4.5
with iproute2-ss000305.

> I'm running iproute2-2.2.4-now-ss001007.tar.gz from
> ftp://ftp.inr.ac.ru, with kernel 2.4.5.
> 
> My userland utilities, like ifconfig, ifup, etc are from RH6.2ish.
> Would they make a difference?


Greetings,
Juri

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Re: [LARTC] Policy routing missing default table?

[Adrian Chung]

On Tue, Jun 05, 2001 at 02:04:01PM +0200, Juri Haberland wrote:
> > I was under the impression that my 3 main tables should have been
> > 'local', 'main', and 'default'.  'main' would contain routes to adjacent
> > networks, and 'default' would contain default routes.  So I could have
> > solved my problem by just creating a table with precidence in between
> > main and default, and changed the default gateway for 192.62.100.0/24
> > without changing network routes too.
> 
> Well, according to the "Linux 2.4 Advanced Routing HOWTO" the default
> table (or 253) should be empty and the default route should be in
> 'main'.

Hmm, that's strange.  So in the situation I have, where the router is
connected to 3 adjacent networks physically, and I only want to alter
the default gateway for one subnet, without affecting the other local
network routes, how would I do it?

I'm assuming that if I insert a table before 'main', as I currently
do, I have to duplicate all the routes to other local networks.

If I add the table after 'main', the default route that's in main
overrides whatever default route I would put in the new table.

Is this logic sensible?

> > Does this make sense?  And if so, does anyone know why I have a table
> > '253' with nothing in it, and no 'default'?
> 
> Actually, I don't know why there isn't a default table but one named
> '253'. I have the same here on a RedHat 7.1 system running kernel 2.4.5
> with iproute2-ss000305.

Okay, at least I'm not alone. :)

--
Adrian Chung (adrian at enfusion-group dot com)
http://www.enfusion-group.com/~adrian
GPG Fingerprint: C620 C8EA 86BA 79CC 384C E7BE A10C 353B 919D 1A17
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Re: [LARTC] Policy routing missing default table?

[Juri Haberland]

Adrian Chung wrote:
> 
> On Tue, Jun 05, 2001 at 02:04:01PM +0200, Juri Haberland wrote:
> > > I was under the impression that my 3 main tables should have been
> > > 'local', 'main', and 'default'.  'main' would contain routes to adjacent
> > > networks, and 'default' would contain default routes.  So I could have
> > > solved my problem by just creating a table with precidence in between
> > > main and default, and changed the default gateway for 192.62.100.0/24
> > > without changing network routes too.
> >
> > Well, according to the "Linux 2.4 Advanced Routing HOWTO" the default
> > table (or 253) should be empty and the default route should be in
> > 'main'.
> 
> Hmm, that's strange.  So in the situation I have, where the router is
> connected to 3 adjacent networks physically, and I only want to alter
> the default gateway for one subnet, without affecting the other local
> network routes, how would I do it?
> 
> I'm assuming that if I insert a table before 'main', as I currently
> do, I have to duplicate all the routes to other local networks.
> 
> If I add the table after 'main', the default route that's in main
> overrides whatever default route I would put in the new table.
> 
> Is this logic sensible?

I assume so. Actually I'm in a similar situation as you and I'm just
about using 'ip' to set up a default route for our backup internet link,
which has (for historical reasons) also a subnet with DMZ associated
with it.

Juri

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