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List:       dhcp-users
Subject:    Re: How to avoid multiple DHCP request forward to all Servers?
From:       Thomas Markwalder <tmark () isc ! org>
Date:       2017-04-07 10:31:27
Message-ID: c555b09c-b524-bd61-20c0-3d96b5fcda1b () isc ! org
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On 4/7/17 5:13 AM, Simon Hobson wrote:
> priyankrathi <priyankrathi731@gmail.com> wrote:
> 
> > While observing the packet capture, I found that both the relay agent is
> > forwarding the request received from Client1 the server multiple times.
> > Similarly, the request from Client2 is also forwarded to the server multiple
> > times. 
> > My assumption is when a request comes on from Client1 from R:eth1 it
> > forwards the packet from R:eth3. As the same time, the second relay which is
> > running on R:eth2 and R:eth3 also listens to the packets and try again
> > forward it to the server. Request from any for the client gets looped
> > between both the relay agents and forwarded multiple times to server.
> > Basically, both relay agent starts flooding the network unless the max hop
> > count of the packet becomes zero.
> Yes, that would probably be the case. Bear in mind that you do NOT need to run \
> multiple relay agents for this, it gains you nothing in terms of functionality, but \
> creates more work and problems like the one you've found. 
> So I'll repeat the question : what is it that you are trying to achieve that makes \
> you think you need this setup ? 
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> dhcp-users@lists.isc.org
> https://lists.isc.org/mailman/listinfo/dhcp-users

As of 4.3.5, dhcrelay supports two new command line options which allow
you to specify interfaces as upstream or downstream only.  This can be
effective in eliminating reflections:

       -iu ifname
              Specifies an upstream network interface: an interface from
which
              replies  from  servers  and other relay agents will be
accepted.
              Multiple interfaces may be specified by using more than
one  -iu
              option.  This argument is intended  to  be used in conjunction
              with one or more -i or -id arguments.

       -id ifname
              Specifies a downstream  network  interface:  an 
interface  from
              which  requests  from  clients  and  other  relay agents
will be
              accepted.  Multiple interfaces may be specified  by 
using  more
              than  one  -id  option.  This argument is intended to be
used in
              conjunction with one or more -i or -iu arguments.








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