Hi,

 

In my scenario there are 2 hosts having same IP address (10.0.0.2/8) wants to communicate with a linux server having 2 vlan interfaces( eth0.10,eth0.20) with same IP address(10.0.0.1/8).

 

 

Maybe you shed some light on this. I'm wondering a bit. Imagine me
being a kernel having a IP packet to deliver. The first thing I do is I
look through my routing table and check what interface I need to to
blow the packet out. (It can be done as u r having separate routing table for each interface (Because of VRF)
 
Once I know that I check my ARP table for any entries. When there is a
static entry, there was already someone who cared for me (i.e. the
administrator). When there is a dynamic entry I grab the MAC address
from the table and send the packet there. (Now here is the problem. U want to contact Host B, But there is a dynamic entry for Host A in the ARP table as below.

10.0.0.2 0x1 0x2 01:23:45:67:89:AB

Host B also having the same IP address so u start to communicate with Host A.

Hope U got my point.

So what U need is a separate ARP table for each interface as U know through which interface u want to communicate.

 

 

 

Hope U got what is my problem.

 

Regards

 

Jaison

 



On 9/11/05, Dirk Tilger <[EMAIL PROTECTED]> wrote:
--- Jaison Jose < [EMAIL PROTECTED]> wrote:
>  I am talking about the dynamic ARP table which we can find in
> /proc/net/arp. This is the only cache where kernel is checking for
> ARP in
> fedora core. But while implementing VRF (Virtual Routing and
> Forwarding)
> there are chances for hosts with same ip in different VLANs. So I
> want to
> keep different ARP tables for each Ethernet interface like
> /proc/net/eth0/arp and /proc/net/eth1/arp for proper communication.
> BSD is
> having this feature but fedora don't.

Maybe you shed some light on this. I'm wondering a bit. Imagine me
being a kernel having a IP packet to deliver. The first thing I do is I
look through my routing table and check what interface I need to to
blow the packet out.

Once I know that I check my ARP table for any entries. When there is a
static entry, there was already someone who cared for me (i.e. the
administrator). When there is a dynamic entry I grab the MAC address
from the table and send the packet there.

If there is no entry, I send a request on the interface the IP address
is routed to. Either there is a is an answer than I know the MAC
address or there is no answer then I don't know it and I can't deliver
the packet.

I don't see the point where I need to know for which interface I
grabbed the MAC address when I am not a bridge. Oh am I a bridge as
well in your case (didn't quickly find something reasonable with goodle
about VRF)? When I bridge between VLANs why should I have VLANs then
other then for filtering? Am I a filtering bridge? Why should I care
about ARP packets then?

Apart from that, look what I see in my ARP table (Gentoo ~x86):
[EMAIL PROTECTED] ~ $ cat /proc/net/arp
IP address       HW type     Flags       HW address            Mask   
Device
192.2.0.2     0x1         0x2         01:23:45:67:89:AB     *      
ra0

[EMAIL PROTECTED] ~ $ uname -a
Linux junge 2.6.12-gentoo-r9 #1 Wed Aug 24 15:09:22 GST 2005 i686
Celeron (Coppermine) GenuineIntel GNU/Linux

Dirk.


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