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Re: routing problem?
- To: Cedar Cox <cedarc(at-nospam)visionforisrael.com>
- Subject: Re: routing problem?
- From: Dani Arbel <darbel(at-nospam)techunix.technion.ac.il>
- Date: Tue, 4 Sep 2001 21:19:57 +0300 (IDT)
- Cc: <linux-il(at-nospam)linux.org.il>
- Delivered-To: linux.org.il-linux-il@linux.org.il
- In-Reply-To: <Pine.LNX.4.21.0109041624490.19008-100000@nanu.visionforisrael.com>
- Sender: linux-il-bounce(at-nospam)cs.huji.ac.il
Cedar,
You could simplify the table if you use only class C (255.255.255.0) masks
for 192.168 networks. . now, if you follow the ADSL howto, your B and C
hosts get the default routes pointing to the internet. to ensure
connectivity to the other side of the VPN you had better use 192.168 net
for the cipcb0 , and rearange the nets:
192.168.0 and 192.168.1 on B (eth0 and eth1)
192.168.2 on C
take 192.168.4 to be for the vpn (cipcb0)
(b is 192.168.4.1 and c 192.168.4.2)
now for c you add the route 192.168.0.0 255.255.254.0 192.168.4.1
and for b you add the route 192.168.2.0 255.255.255.0 192.168.4.2
avoid using net 10 for anything but the ADSL connection.
and I still think you have another kind of problem.
Dani
On Tue, 4 Sep 2001, Cedar Cox wrote:
>
> About the routing table, that's what I thought, although I'm not sure how
> they could be simplified. If I understand correctly, 10.0.1.2 should have
> nothing to do with 10.0.0.0, but not the other way around. Someone
> correct me if I'm wrong, but route's Genmask doesn't really have anything
> to do with the interface's netmask, does it? For example, B has is
> connected to two ethernets (192.168.1.0 and 192.168.10.0) and C to only
> one (192.168.2.0). Is it correct to put a route on C like :
>
> Destination Gateway Genmask Flags Metric Ref Iface
> 192.168.0.0 10.0.1.1 255.255.240.0 UG 0 0 cipcb0
>
> or should it be
>
> 192.168.1.0 10.0.1.1 255.255.255.0 UG 0 0 cipcb0
> 192.168.10.0 10.0.1.1 255.255.255.0 UG 0 0 cipcb0
>
> I hoped to avoid the second case so I don't have to touch C when I add
> another network to B.
>
> I failed to mention that eth2 (and eth1 on C) have nothing to do with the
> cipcb0 interfaces. These are actually used for the ADSL "modems".
> Perhaps a little art will explain:
>
> /---\
> | A |
> \___/
> |
> |
> eth0=/---\
> | B |=eth2-----[ADSL modem]
> eth1=\___/ ||
> | ppp0------------ Internet
> | ||
> /---\ cipcb0-----\
> | Z | |
> \___/ |
> |
> |
> |
> /---\ |
> | E | cipcb0-----/
> \___/ ||
> | ppp0------------ Internet
> | /---\ ||
> *--eth0=| C |=eth1-----[ADSL modem]
> | \___/
> |
> /---\
> | D |
> \___/
>
> B eth0 is 192.168. 1.1 / 255.255.255.0
> B eth1 is 192.168.10.1 / 255.255.240.0
>
> C eth0 is 192.168. 2.1 / 255.255.255.0
>
> B eth2 is 10.200.1.1 / 255.0.0.0
> C eth1 is 10.200.1.1 / 255.0.0.0
> (ADSL eth interfaces are set up from the adsl howto)
>
> B cipcb0 is 10.0.1.1 / 255.255.255.255 P-t-P 10.0.1.2
> C cipcb0 is 10.0.1.2 / 255.255.255.255 P-t-P 10.0.1.1
>
> I think B-eth1 should be /255.255.255.0 instead of /20, as well as a route
> to 192.168.0.0/20 by eth1. I did this, but no change.. no surprise.
>
> At Henry's suggestion, I did a traceroute from E to A (D has a simi-broken
> network setup, but still works.. I don't want to reinstall window right
> now..). I get basically the reverse (from D or E)
>
> traceroute to A
> 1 C (192.168.2.3) <10 ms <10 ms <10 ms
> 2 * * *
> 3 A (192.168.2.2) 62 ms 64 ms 58 ms
>
> Again, ping works fine. I really don't know where to start with tcpdump
> and how to look for path mtu discovery problems, but I supposed TIYFT
> (tcpdump is your friend too). Tell me what to do/look for and I'll give
> it a shot (I do have tcpdump).
>
> -Cedar
>
>
> On Tue, 4 Sep 2001, Dani Arbel wrote:
>
> > Cedar,
> > maybe you might have some path mtu discovery problem?
> > try to tcpdump/ethereal on B and C and see what hapens.
> >
> > About the routing table:
> > more specific routes has precedence when being looked on for routing, so
> > the routing tables look ok (though may be simplified).
> > Dani
> >
> > On Mon, 3 Sep 2001, Cedar Cox wrote:
> >
> > >
> > > I'm not exactly sure what's going on here. This is the setup:
> > >
> > > A ==== B -------- C ==== D
> > >
> > > A, B, and C are running linux, D happens to be a running windows, if it
> > > matters. The A-B link is ethernet, as is C-D. B-C is a CIPE link over
> > > the internet (a VPN).
> > >
> > > A is 192.168.1.4
> > > B is 192.168.1.1 and 10.0.1.1
> > > C is 192.168.2.1 and 10.0.1.2
> > > D is 192.168.2.2
> > >
> > > I have the default route on A pointing to B, on D pointing to C. On B I
> > > have:
> > >
> > > Destination Gateway Genmask Flags Metric Ref Iface
> > > 10.0.1.2 * 255.255.255.255 UH 0 0 cipcb0
> > > 192.168.2.0 10.0.1.2 255.255.255.0 UG 0 0 cipcb0
> > > 192.168.1.0 * 255.255.255.0 U 0 0 eth0
> > > 192.168.0.0 * 255.255.240.0 U 0 0 eth1
> > > 10.0.0.0 * 255.0.0.0 U 0 0 eth2
> > > loopback * 255.0.0.0 U 0 0 lo
> > >
> > > On C I have:
> > >
> > > Destination Gateway Genmask Flags Metric Ref Iface
> > > 10.0.1.1 * 255.255.255.255 UH 0 0 cipcb0
> > > 192.168.2.0 * 255.255.255.0 U 0 0 eth0
> > > 192.168.0.0 10.0.1.1 255.255.240.0 UG 0 0 cipcb0
> > > 10.0.0.0 * 255.0.0.0 U 0 0 eth1
> > > loopback * 255.0.0.0 U 0 0 lo
> > >
> > >
> > > What I can't do is telnet from B to D (port 5800.. VNC), but I can telnet
> > > from A to D. I'm not sure how I might have messed up my routing or
> > > something else. Maybe it's my Genmask's. The "strange" thing is that I
> > > can ping D from A or B without problem. A traceroute from A to D looks
> > > like:
> > >
> > > traceroute to D
> > > 1 B (192.168.1.4) 2.514 ms 1.572 ms 1.229 ms
> > > 2 * * *
> > > 3 D (192.168.2.2) 62.168 ms 64.307 ms 58.755 ms
> > >
> > > If this is not enough information, just say so and I'll give more. Maybe
> > > I'll get creative and draw some ascii art of the big picture.. :)
> > >
> > > Thanks
> > > -Cedar
> > >
>
>
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