Routing of outgoing packets
2010/10/1 Mitja Mihelič <mitja.mihelic@arnes.si>:
>
> On 09/30/2010 05:02 PM, John Doe wrote:
>> From: Mitja Mihelič<mitja.mihelic@arnes.si>
>>> I am trying to use hping to chek the latency of our network.
>>> Somehow things are not going to plan and I thought someone might be able
>>> to shed some light on the subject.
>>> Here is the setup:
>>> (the IP addresses gvien here are fake, but they do represent the correct
>>> state of the networking setup)
>>> vlan * * *interface * * *IP * * * * * * * * * * *mask
>>> V2 * * * *eth0 * * * * * 192.168.20.20 * *32
>>> V4 * * * *eth1 * * * * * 172.16.4.40 * * * *32
>>> V6 * * * *eth2 * * * * * 172.16.6.60 * * * *32
>>>
>>> The default route is set to eth1.
>>> The idea is to use eth2 for pinging only, the other two interfaces are
>>> used by another service and management access.
>> Could you show the ifconfig and route outputs...?
>>
>> JD
> The Centos version is 5.5.
>
> This is the kernel we are using
> (http://rpms.mcnc.org/web100/el5/distro-compat/i386/):
> 2.6.18-164.15.1.el5.web100PAE #1 SMP Mon May 17 17:01:51 EDT 2010 i686
> athlon i386 GNU/Linux
>
> The IP addresses are presented as private addresses, netmasks are real.
>
> Here is the ifconfig output:
> [root@server ~]# ifconfig
> eth0 * * *Link encap:Ethernet *HWaddr 00:16:35:82:45:A0
> * * * * * inet addr:192.168.254.236 *Bcast:192.168.254.239
> Mask:255.255.255.240
> * * * * * inet6 addr: fe80::216:35ff:fe82:45a0/64 Scope:Link
> * * * * * UP BROADCAST RUNNING MULTICAST *MTU:1500 *Metric:1
> * * * * * RX packets:139602 errors:0 dropped:0 overruns:0 frame:0
> * * * * * TX packets:58914 errors:0 dropped:0 overruns:0 carrier:0
> * * * * * collisions:0 txqueuelen:1000
> * * * * * RX bytes:211203420 (201.4 MiB) *TX bytes:4285647 (4.0 MiB)
> * * * * * Interrupt:186 Memory:dc000000-dc012800
>
> eth1 * * *Link encap:Ethernet *HWaddr 00:16:35:82:45:A2
> * * * * * inet addr:192.168.254.244 *Bcast:192.168.254.247
> Mask:255.255.255.248
> * * * * * inet6 addr: fe80::216:35ff:fe82:45a2/64 Scope:Link
> * * * * * UP BROADCAST RUNNING MULTICAST *MTU:1500 *Metric:1
> * * * * * RX packets:15 errors:0 dropped:0 overruns:0 frame:0
> * * * * * TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
> * * * * * collisions:0 txqueuelen:1000
> * * * * * RX bytes:1130 (1.1 KiB) *TX bytes:1116 (1.0 KiB)
> * * * * * Interrupt:194 Memory:da000000-da012800
>
> eth2 * * *Link encap:Ethernet *HWaddr 00:15:17:C5:84:4D
> * * * * * inet addr:192.168.254.18 *Bcast:192.168.254.23
> Mask:255.255.255.248
> * * * * * inet6 addr: fe80::215:17ff:fec5:844d/64 Scope:Link
> * * * * * UP BROADCAST RUNNING MULTICAST *MTU:1500 *Metric:1
> * * * * * RX packets:29 errors:0 dropped:0 overruns:0 frame:0
> * * * * * TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
> * * * * * collisions:0 txqueuelen:1000
> * * * * * RX bytes:2280 (2.2 KiB) *TX bytes:1236 (1.2 KiB)
> * * * * * Memory:dfde0000-dfe00000
>
> lo * * * *Link encap:Local Loopback
> * * * * * inet addr:127.0.0.1 *Mask:255.0.0.0
> * * * * * inet6 addr: ::1/128 Scope:Host
> * * * * * UP LOOPBACK RUNNING *MTU:16436 *Metric:1
> * * * * * RX packets:21 errors:0 dropped:0 overruns:0 frame:0
> * * * * * TX packets:21 errors:0 dropped:0 overruns:0 carrier:0
> * * * * * collisions:0 txqueuelen:0
> * * * * * RX bytes:4240 (4.1 KiB) *TX bytes:4240 (4.1 KiB)
>
>
> And the route command output:
> [root@server ~]# route -n
> Kernel IP routing table
> Destination * * *Gateway * * * * *Genmask * * * * *Flags Metric Ref
> Use Iface
> 192.168.18.122 * 192.168.254.225 *255.255.255.255 *UGH * 0 * * *0
> 0 eth0
> 192.168.254.16 * 0.0.0.0 * * * * *255.255.255.248 *U * * 0 * * *0
> 0 eth2
> 192.168.254.240 *0.0.0.0 * * * * *255.255.255.248 *U * * 0 * * *0
> 0 eth1
> 192.168.18.160 * 192.168.254.225 *255.255.255.240 *UG * *0 * * *0
> 0 eth0
> 192.168.254.224 *0.0.0.0 * * * * *255.255.255.240 *U * * 0 * * *0
> 0 eth0
> 192.168.1.64 * * 192.168.254.225 *255.255.255.192 *UG * *0 * * *0
> 0 eth0
> 192.168.1.128 * *192.168.254.225 *255.255.255.128 *UG * *0 * * *0
> 0 eth0
> 169.254.0.0 * * *0.0.0.0 * * * * *255.255.0.0 * * *U * * 0 * * *0
> 0 eth2
> 0.0.0.0 * * * * *192.168.254.241 *0.0.0.0 * * * * *UG * *0 * * *0
> 0 eth1
>
> --
> Mitja
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This may be too late, but came across this searching for my old
iproute conversations.
Each NIC needs its own "source based route" otherwise, it will use the
sytem wide default route.
In other words, add "nic specific default routes" in addition to the
"system wide default route".
Once you have nic specific source routes, you may notice a big
difference between the following two seemingly identical commands:
ping -I eth2 208.67.222.222
ping -I 192.168.x.y 208.67.222.222
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