Multiple Interfaces Issue

Seth Mos knuffie at xs4all.nl
Tue Dec 31 12:32:00 CST 2002


At 11:30 31-12-2002 -0600, Marco Obaid wrote:
>I do have all the errata updates installed. The systems is up-to-date.
>If the problem is with the Redhat network control scripts, what is the remedy?
>
>As far as the suggestion to do:
>ifconfig eth0 10.10.10.5
>ifconfig eth1 10.10.10.6
>route add default gw 10.10.10.1
>
>I tried it and no luck ...

Strange

> >Is it possible that you have the reverse path filter (used to protect
> >against spoofing) switched on? This might cause "weird" behaviour on
> >multihomed crossing networks.
>
>I am not sure how to turn that on/off ...

#IP spoofing get lost!
  #This is the best method: turn on Source Address Verification and get
  # spoof protection on all current and future interfaces.
  if [ -e /proc/sys/net/ipv4/conf/all/rp_filter ]; then
  echo -n "Setting up IP spoofing protection..."
  for f in /proc/sys/net/ipv4/conf/*/rp_filter; do
  echo 1 > $f
  done
  echo "done."
  else
  echo PROBLEMS SETTING UP IP SPOOFING PROTECTION. BE WORRIED.
  echo "CONTROL-D will exit from this shell and continue system startup."
  echo
  # Start a single user shell on the console
  /sbin/sulogin $CONSOLE
fi

>There is a need now
>to add an additional task to this server which requires a new IP address and
>this  how it all started.

cd /etc/sysconfig/network-scripts
cp ifcfg-eth0 ifcfg-eth0:0
edit ifcfg-eth0:0 (don't forget to edit the device entry to eth0:0 as well!)

ifup eth0:0

ifconfig -a

>By the way, out of desperation I installed Redhat 7.3 to a spare PC, which 
>has
>2 3Com905B NICs. I used the same Redhat Linux media shipped with my PowerEdge
>server. To my surprise, the same issue exists. I numbered one NIC 192.168.0.1
>and the other 192.168.0.5. Only 192.168.0.1 is pingable from the outside, 
>which
>is eth0.

Very peculiar behaviour. This should work out of the box. It should at 
least provide entries in the route table for multiple interfaces.

This is taken from a Red Hat Linux 7.3 machines with 3 network cards (1 
shown) and also functions as the default router for our network. This is 
the only machine that knows about all routes inside the lan. It is known by 
3 IP addresses here. 225 is the main address the other 2 are the ip 
addresses that all the other machines and clients know as the default router.

This is not a "multiple network card connected to same network" example though.

Is there a specific reason that you need a second network card in the 
machine for this task. Do you really need this much bandwidth?
Have you tried setting 2 entirely different networks on the different 
network cards?

Example 10.10.10.5 and 10.10.11.6. Multiple networks on the same wire can 
get ugly very fast though. Better stick to just making an alias or using a 
second network card.

eth1      Link encap:Ethernet  HWaddr 00:02:B3:2F:17:BB
           inet addr:10.0.1.225  Bcast:10.0.3.255  Mask:255.255.252.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:2668325 errors:0 dropped:0 overruns:0 frame:0
           TX packets:2288021 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:100
           RX bytes:1877693703 (1790.7 Mb)  TX bytes:1015937545 (968.8 Mb)
           Interrupt:18 Base address:0x8000

eth1:1    Link encap:Ethernet  HWaddr 00:02:B3:2F:17:BB
           inet addr:10.0.1.254  Bcast:10.0.3.255  Mask:255.255.252.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:18 Base address:0x8000

eth1:2    Link encap:Ethernet  HWaddr 00:02:B3:2F:17:BB
           inet addr:10.0.3.254  Bcast:10.0.3.255  Mask:255.255.252.0
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           Interrupt:18 Base address:0x8000

route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
10.0.0.0        10.0.1.225      255.255.252.0   UG    0      0        0 eth1
10.0.0.0        0.0.0.0         255.255.252.0   U     0      0        0 eth1
10.2.0.0        10.0.1.240      255.255.0.0     UG    0      0        0 eth1
127.0.0.0       0.0.0.0         255.0.0.0       U     0      0        0 lo
0.0.0.0         xxx.xxx.xxx.xx  0.0.0.0         UG    0      0        0 eth2

Cheers

--
Seth
It might just be your lucky day, if you only knew.




More information about the Linux-PowerEdge mailing list