for packet routing puzzle lovers--aka, routing problem
Brad Bonkoski
plug-discuss@lists.plug.phoenix.az.us
Tue, 07 May 2002 18:00:43 -0700
I think the problem is that you are configuring both as "gateways", so box 'A' is saying "I want to get to 192.168.0.10" if I look at my
routing table, the default gateway is "226-4-216-1.ge.." so that is what I will do. Of course this drops the packet because this is a
private block (non-routable to most "real-world" routers). So, short of the theory, add a network route, but don't make it a agteway
and see if that works...
i.e. on bax 'A'
route add -net 192.168.0.0 netmask 255.255.255.0 10.0.0.2
and on box 'C'
route add -net 10.0.0.1 netmask 255.0.0.0 192.168.0.1
(of course you should flush the routing tables to begin with)
I would presume this would work, and it appears the internal route (box B) is configured correctly, of course you might want to make
sure ip_forwarding is turned on :-)
echo "1" > /path/to/ip_forward (I *think* /proc/sys/net/ip_forward)
HTH
-Brad
Eric wrote:
> This stuff is supposed to be basic but it gets confusing. Could someone
> help me understand a routing problem? I very much appreciate it; I know
> there are lots of characters on this page. But this problem is preventing
> me from scp'ing from my firewall (computer C) to fileserver (computer A),
> which is what I need to do.
>
> Topology
>
> Computer A (e-smith)
> eth1 public ip
> eth0 10.0.0.1
>
> Computer B (w2K)
> 10.0.0.2
> 192.168.0.1
>
> Computer C (rh7.1)
> 192.168.0.10
>
> Computers A and C are obviously separated by computer B.
>
> PROBLEM:
>
> Computer A can ping only 10.0.0.2 and public IP's, but not anything on
> 192.168.0.x.
> Computer B can ping everything.
> Computer C can ping anything on 192.168.0.x and any public IP, but
> **cannot** ping any 10.0.0.x.
>
> **So in essence, A cannot reach C, and C cannot reach A.
>
> I told computer C how to get to A, and A how to get to C, and B how to get
> to A and C. But it doesn't work. What am I doing wrong.
>
> Here are the routing tables:
>
> ***Computer A
> Kernel IP routing table
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use
> Iface
> 10.0.0.0 * 255.255.255.0 U 0 0 0 eth0
> 192.168.0.0 pc-0002 255.255.255.0 UG 0 0 0 eth0
> 226.4.216.0 * 255.255.255.0 U 0 0 0 eth1
> 127.0.0.0 * 255.0.0.0 U 0 0 0 lo
> default 226-4-216-1.ge 0.0.0.0 UG 0 0 0 eth1
>
> ("pc-0002" showed up after I did "route add -net 192.168.0.0/24 gw
> 10.0.0.2".)
>
> ***Computer B
> Active Routes:
> Network Destination Netmask Gateway Interface Metric
> 0.0.0.0 0.0.0.0 10.0.0.1 10.0.0.2 1
> 10.0.0.0 255.255.255.0 10.0.0.2 10.0.0.2 1
> 10.0.0.0 255.0.0.0 192.168.0.2 192.168.0.1 1
> 10.0.0.2 255.255.255.255 127.0.0.1 127.0.0.1 1
> 10.255.255.255 255.255.255.255 10.0.0.2 10.0.0.2 1
> 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
> 192.168.0.0 255.255.255.0 192.168.0.1 192.168.0.1 1
> 192.168.0.0 255.255.255.0 10.0.0.2 10.0.0.2 1
> 192.168.0.1 255.255.255.255 127.0.0.1 127.0.0.1 1
> 192.168.0.255 255.255.255.255 192.168.0.1 192.168.0.1 1
> 224.0.0.0 224.0.0.0 10.0.0.2 10.0.0.2 1
> 224.0.0.0 224.0.0.0 192.168.0.1 192.168.0.1 1
> 255.255.255.255 255.255.255.255 10.0.0.2 10.0.0.2 1
> Default Gateway: 10.0.0.1
> ===========================================================================
> Persistent Routes:
> Network Address Netmask Gateway Address Metric
> 10.0.0.0 255.0.0.0 192.168.0.2 1
>
> ***Computer C
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use
> Iface
> 192.168.0.0 * 255.255.255.0 U 0 0 0 eth0
> 10.0.0.0 192.168.0.1 255.0.0.0 UG 0 0 0 eth0
> 127.0.0.0 * 255.0.0.0 U 0 0 0 lo
> default 192.168.0.1 0.0.0.0 UG 0 0 0 eth0
>
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