Problem Routing SLES 11 SP3

SUSE Linux Enterprise Server SLES Networking
1

Hello,
i have a strange routing problem under SLES 11 SP3.

I have the following network interface settings:
eth1 Link encap:Ethernet HWaddr AC:16:2D:6F:7E:F1
inet addr:192.168.10.56 Bcast:192.168.10.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1952841 errors:0 dropped:5520 overruns:0 frame:0
TX packets:587477 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:522637737 (498.4 Mb) TX bytes:793376827 (756.6 Mb)
Interrupt:37

And these Routing Table:
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.10.250 0.0.0.0 UG 0 0 0 eth1
127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
192.168.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1

The 192.168.10.250 is our default Gateway for the whole network.
There are more than 500 Hosts using these Gateway.

Only on these Server SLES Server I have a problem to reach some networks.
Some IPs work, some doesnt work.

Here an example traceroute to an IP Addresses in our Subnet 192.168.8.0/24

Working correct:
traceroute to 192.168.8.170 (192.168.8.170), 30 hops max, 40 byte packets using UDP
1 192.168.10.250 (192.168.10.250) 0.359 ms 0.116 ms 0.088 ms
2 192.168.8.170 (192.168.8.170) 2.545 ms * *

Not Working:
traceroute to 192.168.8.62 (192.168.8.62), 30 hops max, 40 byte packets using UD P
1 * * *
2 * * *
3 * * *
4 * * *
5 * * *
6 * * *
7 * * *
8 * * *
^C

Sometimes some hots work, sometimes they don`t.

I also try to use another network interface.

I don’t have any idea what causes these problem.
Please help me! :wink:

Thanks
Jörg

2

Ein ähnliches Problem hatten wir unter einem CENTOS Server.

Da hat das hier geholfen.

/etc/sysctl.conf

Controls IP packet forwarding

net.ipv4.ip_forward = 1

Unter SLES mit
/etc/sysctl.conf

Controls IP packet forwarding

net.ipv4.conf.all.forwarding = 1

ändert sich aber nichts am Verhalten

3

Hi Jörg,

have you had a look at the corresponding tcpdump / wireshark output, to see if your box is sending proper ICMP requests to the correct gateway (check the destination MAC of the ICMP requests).

And you may want to take a look at the ARP table of the server, to check for stray entries (whereever these may have come from - if they’re there, we’ll try to find out :wink: )

Regards,
J