Re: A PC with two NIC routing problem

Exactly!!! you have reverse path reature turned on!

try following commands, to quickly check if your problem related to RPF:
echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter
echo 1 > /proc/sys/net/ipv4/conf/eth0/rp_filter
echo 1 > /proc/sys/net/ipv4/conf/eth1/rp_filter

If ping will seccess, you should turn rp_filter off in your conf
files. Depending on your linmux distro it may be /etc/sysctl.conf. You
may need to add, or uncomment followwing line to your sysctl.conf
file:
net.ipv4.conf.default.rp_filter=0, or refer to your distro
documentation for setting sysctl variables.

On Sat, Oct 2, 2010 at 1:40 AM, Jack <ccie.unnumbered_at_gmail.com> wrote:
> root_at_vault2:~# cat /proc/sys/net/ipv4/conf/all/rp_filter
> 1
> root_at_vault2:~# cat /proc/sys/net/ipv4/conf/eth0/rp_filter
> 1
> root_at_vault2:~# cat /proc/sys/net/ipv4/conf/eth1/rp_filter
> 1
> root_at_vault2:~#
>
>
> On 10/01/2010 05:22 PM, Sergey Matashuk wrote:
>>
>> I guest there might be reverse path filtering applied on linux
>> machine. Some linux distributions have it enabled by default.
>>
>> Can you show output of command "cat
>> /proc/sys/net/ipv4/conf/all/rp_filter" and "cat
>> /proc/sys/net/ipv4/conf/<INTERFACE_HERE>/rp_filter" from you linux
>> box?
>>
>>
>> On Fri, Oct 1, 2010 at 8:55 PM, Jack<ccie.unnumbered_at_gmail.com> wrote:
>>
>>>
>>> Yes, 10.10.10.1 and 11.11.11.1 respectively.
>>>
>>> On 10/01/2010 01:41 PM, Sergey Matashuk wrote:
>>>
>>>>
>>>> do host10 and host11 have defult gateway configured?
>>>>
>>>> On Fri, Oct 1, 2010 at 8:32 PM, Jack<ccie.unnumbered_at_gmail.com>
>>>> wrote:
>>>>
>>>>
>>>>>
>>>>> A linux PC has two NIC cards:
>>>>> eth0=10.10.10.100/24 belongs to VLAN 10
>>>>> eth1=11.11.11.100/24 belongs to VLAN 11
>>>>> the default gateway is 10.10.10.1
>>>>>
>>>>> A layer 3 switch has the following configuration:
>>>>> int vlan 10
>>>>> ip addr 10.10.10.1 255.255.255.0
>>>>> int vlan 11
>>>>> ip addr 11.11.11.1 255.255.255.0
>>>>>
>>>>>
>>>>> Host10 on vlan 10 with ip address 10.10.10.10/24 can ping 10.10.10.100,
>>>>> but
>>>>> cannot ping 11.11.11.100
>>>>>
>>>>> Host11 on vlan 11 with ip address 11.11.11.11/24 can ping 11.11.11.100,
>>>>> but
>>>>> cannot ping 10.10.10.100
>>>>>
>>>>>
>>>>> How to make the linux PC respond to all pings from both hosts?
>>>>>
>>>>>
>>>>> Thanks,
>>>>> Jack
>>>>>
>>>>>
>>>>> Blogs and organic groups at http://www.ccie.net
>>>>>
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>>>>>
>>>>>
>>>>
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>>>>
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>>>
>>> Blogs and organic groups at http://www.ccie.net
>>>
>>> _______________________________________________________________________
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Received on Sat Oct 02 2010 - 10:35:29 ART