comments below
david
On Wed, 10 Jan 2001, Peter Peltonen wrote:
> David Brett wrote:
> >
> > The possible locations for the problems are:
> >
> > Linux box is not routing properly.
>
> It should be:
>
> # /sbin/route -n
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> 192.168.0.253 0.0.0.0 255.255.255.255 UH 0 0 0 eth1
> x.x.x.253 0.0.0.0 255.255.255.255 UH 0 0 0 eth0
> x.x.x.190 0.0.0.0 255.255.255.255 UH 0 0 0 eth2
> 10.1.2.254 0.0.0.0 255.255.255.255 UH 0 0 0 eth3
> x.x.x.252 0.0.0.0 255.255.255.252 U 0 0 0 eth0
> x.x.x.128 0.0.0.0 255.255.255.128 U 0 0 0 eth2
> 192.168.0.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
> 10.1.2.0 0.0.0.0 255.255.255.0 U 0 0 0 eth3
> 127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
> 0.0.0.0 x.x.x.254 0.0.0.0 UG 0 0 0 eth0
>
> # cat /proc/sys/net/ipv4/ip_forward
> 1
>
>
> > The cisco router is not routing properly. It needs the following
> > statements to work
>
> This is where I expect the problem to be... That my ISP hasn't configured the
> CISCO correctly.
>
> I don't know anything about configuring CISCOs, could you explain a bit here:
>
> > ip route x.x.x.190 255.255.255.128 x.x.x.253
>
> Why does the CISCO need to know the route to x.x.x.190? I mean, shouldn't it
> just send all the packets to my router's eth0 (.253) which will then handle
> the packets?
>
The router has two routes out of it. one to the internet and the second to
your network. Any route it does not know about it will drop or send to
the default route, if it exists. Since the internet is a larger network
the default is the internet and your network not visible to the router is
defined. This is rhe reason for telling the router about your network
behind the linux firewall box.
> Why wouldn't you define the mask for x.x.x.253? It does not matter in which
> network it is? I mean, shouldn't it be in the same network as my eth0 -- using
> mask /30?
cisco routing 101
this is how cisco has designed its routers to work. The structure of the
command is ip network with mask and how to get too it by single ip
address. The reasoning is the router will drop any packets it doesn't
have route for. Unless something tells it about it (routing protocol,
connected device, input route this case) and which device knows how to get
to the network (the single ip address)
>
>
> > The easiest way to test is to do a traceroute from the client.
>
> Okay, here's some traceroute outputs from the client (antarktis):
>
>
> [root@antarktis /root]# traceroute -n x.x.x.190
> traceroute to x.x.x.190 (x.x.x.190), 30 hops max, 38 byte packets
> 1 x.x.x.190 (x.x.x.190) 0.206 ms 0.120 ms 0.114 ms
>
> [root@antarktis /root]# traceroute -n x.x.x.253
> traceroute to x.x.x.253 (x.x.x.253), 30 hops max, 38 byte packets
> 1 x.x.x.253 0.202 ms 0.114 ms 0.113 ms
>
> [root@antarktis /root]# traceroute -n x.x.x.254
> traceroute to x.x.x.254 (x.x.x.254), 30 hops max, 38 byte
> packets
> 1 193.65.111.190 0.195 ms 0.122 ms 0.116 ms
> 2 * * *
*********************
The first place I would look would be at 193.65.11.190. In most cases (as
in not all) the problem is with 193.65.111.190.
**********************
>
>
> Does this mean that my linux box is routing correctly or not?
>
> Peter
>
>
> > On Tue, 9 Jan 2001, Peter Peltonen wrote:
> >
> > > Here we go again...
> > >
> > > I've finally got my ISP to configure the CISCO router. They made "a
> > > a static route for xxx.xx.xxx.128/25 and configured xxx.xx.xxx.253 as a
> > > forwarding router". The network looks like this at the moment:
> > >
> > >
> > > ISP
> > > |
> > > |
> > > HDSL
> > > |
> > > |
> > > CISCO
> > > eth0 ip xxx.xx.xxx.254, mask /??
> > > |
> > > |
> > > eth0 ip xxx.xx.xxx.253, mask /30
> > > LINUX gw xxx.xx.xxx.254
> > > eth1 ip xxx.xx.xxx.190, mask /25
> > > |
> > > |
> > > eth0 ip xxx.xx.xxx.129, mask /25
> > > CLIENT gw xxx.xx.xxx.190
> > >
> > >
> > > But no go. Still the same situation: client can ping linux and vice versa,
> > > but client cannot ping the outside world.
> > >
> > > Could it be possible that my ISP still keeps the CISCO with mask /25 and
> > > that is why my routing fails?
> > >
> > > Maybe I should search for information with tcpdump but I've never used it
> > > before -- could someone give me instructions what to do with it and what to
> > > look for?
> > >
> > >
> > > Cheers,
> > > Peter
>
>
>
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