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From: Alex on 3 Oct 2006 10:50
I have a CentOS 4.3 server with two NICs (see route table and ifconfig
output below). eth0 has an IP address of 192.168.0.12, an eth1 has an
IP address of 192.168.1.10. The server can communicate with anything on
the 192.168.0.0 network, but when I try to ping anything on the
192.168.1.0 network, or anything on the internet, I get

From 192.168.1.10 icmp_seq=0 Destination Host Unreachable

Any idea what the problem may be?

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.2.0 192.168.0.253 255.255.255.0 UG 0 0 0 eth0
192.168.1.0 * 255.255.255.0 U 0 0 0 eth1
192.168.0.0 * 255.255.255.0 U 0 0 0 eth0
169.254.0.0 * 255.255.0.0 U 0 0 0 eth1
default 192.168.1.254 0.0.0.0 UG 0 0 0 eth1


eth0 Link encap:Ethernet HWaddr 00:0C:29:04:9B:B7
inet addr:192.168.0.12 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe04:9bb7/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:187189 errors:0 dropped:0 overruns:0 frame:0
TX packets:10837 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:22779628 (21.7 MiB) TX bytes:2154172 (2.0 MiB)
Interrupt:185 Base address:0x1400

eth1 Link encap:Ethernet HWaddr 00:0C:29:04:9B:C1
inet addr:192.168.1.10 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe04:9bc1/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:186151 errors:0 dropped:0 overruns:0 frame:0
TX packets:458 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:22644864 (21.5 MiB) TX bytes:29376 (28.6 KiB)
Interrupt:169 Base address:0x1480
From: Andrei Ivanov on 3 Oct 2006 16:29
In comp.os.linux.networking Alex <fugtruck(a)yahoo.com> wrote:
> From 192.168.1.10 icmp_seq=0 Destination Host Unreachable

Try to "ping -nb 192.168.1.255". At least one IP address
should give you response (computer's own IP). If nothing
else responds to broadcasts - check cable.

--
andrei
From: Moe Trin on 3 Oct 2006 22:11
[Followup-To: set to c.o.l.networking]

On Tue, 03 Oct 2006, in the Usenet newsgroup comp.os.linux.networking, in
article <6NuUg.8040$GR.3974(a)newssvr29.news.prodigy.net>, Alex wrote:

>I have a CentOS 4.3 server with two NICs (see route table and ifconfig
>output below). eth0 has an IP address of 192.168.0.12, an eth1 has an
>IP address of 192.168.1.10. The server can communicate with anything on
>the 192.168.0.0 network, but when I try to ping anything on the
>192.168.1.0 network, or anything on the internet, I get
>
> From 192.168.1.10 icmp_seq=0 Destination Host Unreachable

That means the network code knows _where_ to send the packets, but when it
tried to ARP for the MAC address of that box, it got no response.

>Kernel IP routing table

Looks fine

>eth0 Link encap:Ethernet HWaddr 00:0C:29:04:9B:B7

[compton ~]$ etherwhois 00:0C:29
00-0C-29 (hex) VMware, Inc.
000C29 (base 16) VMware, Inc.
3145 Porter Dr.
Palo Alto CA 94304
UNITED STATES
[compton ~]$

Oh-oh... Houston, we have a problem.

> RX packets:187189 errors:0 dropped:0 overruns:0 frame:0
> TX packets:10837 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:1000

OK, that looks reasonable

>eth1 Link encap:Ethernet HWaddr 00:0C:29:04:9B:C1

Oh-oh...

> RX packets:186151 errors:0 dropped:0 overruns:0 frame:0
> TX packets:458 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:1000

Well, it's saying that there are packets up the whazoo, so my next step
would be to run tcpdump on eth0 - noting the traffic. But if you look in
the thread "Why does tcpdump show few packet?" in comp.os.linux.networking,
you'll see another individual has been having troubles with dropped
packets, and I've got a fairly strong feeling it's something to do with
VMWare. If possible, I'd also run a sniffer on another host on the
192.168.1.x network, and see what (if any) packets are getting out.

Old guy
From: Walter Mautner on 4 Oct 2006 01:39
Alex enlightened us alt.linux-(ab)users with:

> I have a CentOS 4.3 server with two NICs (see route table and ifconfig
> output below). eth0 has an IP address of 192.168.0.12, an eth1 has an
> IP address of 192.168.1.10. The server can communicate with anything
> on the 192.168.0.0 network, but when I try to ping anything on the
> 192.168.1.0 network, or anything on the internet, I get
>
> From 192.168.1.10 icmp_seq=0 Destination Host Unreachable
>
> Any idea what the problem may be?
>
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref
> Use Iface
> 192.168.2.0 192.168.0.253 255.255.255.0 UG 0 0
> 0 eth0
> 192.168.1.0 * 255.255.255.0 U 0 0
> 0 eth1
> 192.168.0.0 * 255.255.255.0 U 0 0
> 0 eth0
> 169.254.0.0 * 255.255.0.0 U 0 0
> 0 eth1
> default 192.168.1.254 0.0.0.0 UG 0 0
> 0 eth1
>
>
> eth0 Link encap:Ethernet HWaddr 00:0C:29:04:9B:B7
> inet addr:192.168.0.12 Bcast:192.168.0.255
....
> eth1 Link encap:Ethernet HWaddr 00:0C:29:04:9B:C1
> inet addr:192.168.1.10 Bcast:192.168.1.255
....
A setup with 2 nics (though real, one of them wireless) and 2 default
gws here:
Destination Router Genmask Flags Metric Ref
Use Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 35 0 0
ath0
192.168.0.0 0.0.0.0 255.255.255.0 U 10 0 0
eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 10 0 0
eth1
169.254.0.0 0.0.0.0 255.255.0.0 U 35 0 0
ath0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0
lo
0.0.0.0 192.168.0.1 0.0.0.0 UG 10 0 0
eth1
0.0.0.0 192.168.1.1 0.0.0.0 UG 35 0 0
ath0

My interfaces are

ath0 Link encap:Ethernet Hardware Adresse 00:13:F7:15:84:72
inet Adresse:192.168.1.1 Bcast:192.168.1.255
Maske:255.255.255.0
....

eth1 Link encap:Ethernet Hardware Adresse 00:01:02:9F:EB:9D
inet Adresse:192.168.0.10 Bcast:192.168.0.255
Maske:255.255.255.0

Substitute 0.12 for 0.1 here, and 1.10 for 1.1.

I wonder what makes you add IP addresses of 0.253 and 1.254 as gateways
here ...
--
vista policy violation: Microsoft optical mouse found penguin patterns
on mousepad. Partition scan in progress to remove offending
incompatible products. Reactivate MS software.
Linux 2.6.17-mm1,Xorg7.1/nvidia [LinuxCounter#295241,ICQ#4918962]
From: Moe Trin on 4 Oct 2006 16:07
On Wed, 04 Oct 2006, in the Usenet newsgroup comp.os.linux.networking, in
article <g2ubv3-2gf.ln1(a)woodpecker.woodpecker.fdns.net>, Walter Mautner wrote:

>A setup with 2 nics (though real, one of them wireless) and 2 default
>gws here:

Sorry - concept error. A default route is a route that you use when NO
other route leads where you wish to go.

>Destination Router Genmask Flags Metric Ref Use Iface
>192.168.1.0 0.0.0.0 255.255.255.0 U 35 0 0 ath0
>192.168.0.0 0.0.0.0 255.255.255.0 U 10 0 0 eth1
>169.254.0.0 0.0.0.0 255.255.0.0 U 10 0 0 eth1
>169.254.0.0 0.0.0.0 255.255.0.0 U 35 0 0 ath0
>127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
>0.0.0.0 192.168.0.1 0.0.0.0 UG 10 0 0 eth1
>0.0.0.0 192.168.1.1 0.0.0.0 UG 35 0 0 ath0

OK - if you are going to send a packet to 192.168.1.5, the first line says
that address is directly on 'ath0'. If you want to send a packet to
192.168.0.5, the second line says it's directly on 'eth1'. So far, no
problem. Now, send a packet to 169.254.22.55 - which interface do you
use? When there are two (or more) routes that lead to the same place
(here, 169.254.0.0 - 169.254.255.255), the _kernel_ uses ONLY the last
one configured. How about sending to 123.45.67.89 - which interface
will you use? Same answer as above - the _last_ one configured.

>My interfaces are
>
>ath0 Link encap:Ethernet Hardware Adresse 00:13:F7:15:84:72
> inet Adresse:192.168.1.1 Bcast:192.168.1.255 Maske:255.255.255.0

Look at the routing table above. To reach "the world" (that is, any address
not on the local LANs), you say to send the packet to 192.168.1.1, and it
will forward it... but you are 192.168.1.1, so where will you send it next?
The routing table says to send it to 192.168.1.1, and it will forward it...
but you are 192.168.1.1, so where will you send it next? The routing table
says to send it to 192.168.1.1, and it will forward it... but you are
192.168.1.1, so where will you send it next? See the problem? The gateway
address is the address of the REMOTE system you will send the packets to
and have it forward them. It's not your own address.

>I wonder what makes you add IP addresses of 0.253 and 1.254 as gateways
>here ...

Because those are the addresses of the routers that lead to those other
networks. Your routing table should look like:

Destination Router Genmask Flags Metric Ref Use Iface
192.168.1.0 0.0.0.0 255.255.255.0 U 35 0 0 ath0
192.168.0.0 0.0.0.0 255.255.255.0 U 10 0 0 eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
0.0.0.0 192.168.0.1 0.0.0.0 UG 10 0 0 eth1

The 169.254.0.0/16 address is only needed for b0rken windoze boxes that
can't find a DHCP server.

Old guy
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