Mailinglist Archive: opensuse (5100 mails)

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Re: [SLE] routing between subnets
  • From: "Jorge Manuel B. S. Vicetto" <bb+shared.it.lists.suse-e@xxxxxxxxxx>
  • Date: Tue, 22 Jun 2004 02:15:46 +0000
  • Message-id: <20040622021546.nsgoc4w4w0ooww4o@xxxxxxxxxxxxxxx>
Hi Henry.


Quoting Henry Harpending <harpend@xxxxxxxxxxxx>:

On Tue, Jun 22, 2004 at 12:54:14AM +0000, Jorge Manuel B. S. Vicetto wrote:

are your machines capable to ping the printers on the other subnet? From our
discussion I'm supposing they can't. If not, it has to be related to routing.
Can you show us the routing table on one of the machines and the ip
configuration of one of the printers?
And can you post a traceroute from one of the machines to a printer?

Jorge you have the patience of Job. I have converted the two subnets of my
server to be 192.168.1/24 and 192.168.0/24. So here is the server routing
table:


I'm not quite that patient! ;-) I just like networking and everything related to
it and feel that I may be able to help others - or so I would like to think.

Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 192.168.1.2 255.255.255.0 UG 0 0 0 eth0
192.168.0.0 192.168.0.2 255.255.255.0 UG 0 0 0 wlan0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
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 0 0 0 wlan0

The two network cards have addresses 192.168.1.2 (eth0) and 192.168.0.2
(wlan0).

From a machine attached to wlan0 I can ping both cards, I can ping any
machine on wlan0, but I cannot ping anything attached to eth0. The failure
is symmetric: from a laptop attached to eth0 I can ping anything attached to
eth0, I can ping both network cards, but I cannot ping anything attached to
wlan0.

Here is the routing table from a laptop attached to eth0 (i.e. the subnet
where I want to put the printers):

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
192.168.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
0.0.0.0 192.168.0.2 0.0.0.0 UG 0 0 0 eth0


Ander has already identified the problem. Don't forget to update the netmask for
all stations and printers.

I am not sure what traceroutes I should report since I can't get any routes
to work!


For future reference, a traceroute from this station to a printer would let you
see that the station wasn't contacting the gateway. Traceroutes are a very
powerful tool to discover routing problems.
Here's an example:

At home I have a server, atlantis, with the 172.28.2.5 IP address and a gateway,
fw, with the 172.28.2.2 IP address.

fw:~ # ip addr
1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 brd 127.255.255.255 scope host lo
inet6 ::1/128 scope host
2: sit0@NONE: <NOARP> mtu 1480 qdisc noop
link/sit 0.0.0.0 brd 0.0.0.0
3: eth0: <BROADCAST,MULTICAST,PROMISC,UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:04:76:0f:99:59 brd ff:ff:ff:ff:ff:ff
inet 172.28.2.2/24 brd 172.28.2.255 scope global eth0
inet6 fe80::204:76ff:fe0f:9959/64 scope link
4: eth1: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 100
link/ether 00:01:02:fa:e0:9e brd ff:ff:ff:ff:ff:ff
inet 10.0.0.5/24 brd 10.0.0.255 scope global eth1
inet6 fe80::201:2ff:fefa:e09e/64 scope link
fw:~ #

If I try to contact atlantis from fw, this is what I get:

fw:~ # traceroute 172.28.2.5
traceroute to 172.28.2.5 (172.28.2.5), 30 hops max, 40 byte packets
1 atlantis.acores.pt (172.28.2.5) 0.240 ms 0.000 ms 0.000 ms
fw:~ #

If I had two subnets with a /26 mask, so that 172.28.2.100 would be on another
subnet, but didn't use the proper mask I would get something as:

fw:~ # traceroute 172.28.2.100
traceroute to 172.28.2.100 (172.28.2.100), 30 hops max, 40 byte packets
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 fw.acores.pt (172.28.2.2)(H!) 2970.290 ms (H!) 2968.341 ms (H!) 2966.382
ms
fw:~ #

At work I have some servers on a DMZ and a router at the border. When I try to
traceroute an external address, my server starts by contacting my router - with
the 62.48.177.209 IP address.
So this resembles what you should see if your netmask and gateway were correctly
configured:

zeus:~ # traceroute www.yahoo.com
traceroute to www.yahoo.com (216.109.118.75), 30 hops max, 40 byte packets
1 router.esenfah.pt (62.48.177.209) 2.170 ms 1.275 ms 1.504 ms
2 62.48.131.160 63.160 ms 73.028 ms 75.513 ms
3 62.48.131.81 83.119 ms 83.065 ms 85.997 ms
4 adsl-plus-PCS1.ptprime.net (62.48.131.222) 89.454 ms 92.606 ms 101.435
ms
5 lisbon2-br1-a411.cprm.net (195.8.10.81) 96.232 ms 99.979 ms 102.336 ms
6 lisbon1-cr1-p50.cprm.net (195.8.0.89) 105.986 ms 108.902 ms 111.396 ms
7 if-0-0.core1.Miami.Teleglobe.net (207.45.197.197) 187.447 ms 190.679 ms
194.556 ms
8 if-6-0.core2.Ashburn.Teleglobe.net (207.45.223.114) 189.886 ms 193.121 ms
195.806 ms
9 ix-11-0.core2.Ashburn.teleglobe.net (209.58.27.38) 187.925 ms 190.910 ms
194.086 ms
10 vlan221-msr2.dcn.yahoo.com (216.115.96.167) 165.366 ms 165.171 ms
165.422 ms
11 vl33.bas2-m.dcn.yahoo.com (216.109.120.154) 169.381 ms 173.566 ms
UNKNOWN-216-109-120-202.yahoo.com (216.109.120.202) 175.928 ms
12 p12.www.dcn.yahoo.com (216.109.118.75) 179.120 ms 182.773 ms 184.482 ms
zeus:~ #


Best regards, Henry

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I hope this helps someone to get a better understanding on networking and
routing.


------------------------------------------

Jorge Manuel B. S. Vicetto
Network Manager and Systems Administrator
Angra do Heroísmo Nursing School (ESEnfAH)

------------------------------------------

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