Re: Sending ICMP echo request out

["Nikolay S." <nowhere@xxxxxxxxxxxxxxxx>]

В Пт., 09/12/2011 в 00:00 +0530, anil dahiya пишет:
> Hi ,
> 
> I have following setup with routing table as shown below:
> 
> +-----------------------+
> |    System-1      |
> |     "client"         |
> |------------------------|
> |  192.168.11.5   |
> +----------------------+
>        |
>        |
> +------+-----+
> |   Switch   +----------------------+
> +------+-----+                        |
>        |                                 |
>        |                       +-------------------------+
>        |                        |  192.168.11.1      |
>        |                        |---------------------------|
>        |                        |     Router            |
>        |                        |-------------------------- |
>        |                        |   192.168.12.1     |
>        |                       +--------------------------+
>        |                                    |
>        |                                    |
> +------------------------+                |
> |  192.168.11.6      |                |
> |--------------------------|                |
> |   System-2        |                |
> |--------------------------|                |
> |   192.168.12.6    |                |
> |                          |----------------+
> +------------------------+
> 
> Routing table details of setup
> ------------------------------------------
> System-1
> -----
> $route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
> 192.168.11.0    0.0.0.0         255.255.255.0   U     1      0        0 eth1
> 0.0.0.0         192.168.11.1    0.0.0.0         UG    0      0        0 eth1
> 
> 
> Router
> -----------
> $route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
> 192.168.12.0    0.0.0.0         255.255.255.0   U     0      0        0 eth1
> 192.168.11.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0
> 
> 
> System-2
> ------
> $route -n
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
> 192.168.12.0    0.0.0.0         255.255.255.0   U     0      0        0 eth1
> 192.168.11.0    0.0.0.0         255.255.255.0   U     0      0        0 eth0
> 0.0.0.0         192.168.12.1    0.0.0.0         UG    0      0        0 eth1
> 
> 
> When I do ping from system-1 192.168.11.5 to system-2 192.168.12.6 ,
> ping echo packet is reaching on system-2 through NIC 192.168.12.6 but
> system is not sending any response to 192.168.11.5 using either of NIC
> i.e 192.168.11.6 or 192.168.12.6 ? Why this is happening ? Can you
> help me ?
> 
> I have observed same type of symtoms when I do SSH from 192.168.11.5
> to 192.168.12.6
> 
> FYI,
> ip_forwarding is enable on router and iptables are no configured on
> any of system .

I think, reverse path filtering is the problem here.

> 
> Thanks,
> Anil
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