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ajaykumar141229
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Participant
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Registered: ‎05-20-2019

1G and 10G same subnet issue

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Hello all,

I have a zynqmp custom board which has 1G and 10G ethernets,both are working fine when i assign two different ip addresses to each interface like for 10G 172.168.1.xx and for 1G ethernet 182.168.1.xx.

But now my requirement is i want to ping the both ethernet interfaces from local PC when both ip's are configured in the same subnet like 192.168.1.xx for 10G and 192.168.1.xx for 1G in this type of configuration i should able to ping both ethernets from local PC.

 

Please suggest me the way to do this,as of now i am not able to do this.

Regards,

CN Ajay kumar

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shabbirk
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Moderator
118 Views
Registered: ‎12-04-2016

Hi @ajaykumar141229 

One possible method to make it work on the same subnet is to change the routing table/NAT settings.

If you want to have two interfaces on the same machine on the same subnet for redundancy/stability purposes, network bonding is another solution

 

Regards

Shabbir

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rfs613
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Scholar
174 Views
Registered: ‎05-28-2013

This is actually a very common networking question on any system with more than one NIC (= ethernet port). In this regard, there is nothing special about the ZynqMP, or the fact that your interfaces are different speed (1G and 10G).

The operating system normally looks at only the destination IP address when it sends out a packet. There is a "routing table" (you can use "route -n" to see it) which determines the subnet handled by each interface. Implicit in this is that each interface serves a separate subnet.

If you have multiple interfaces in the same subnet, the routing table entries will overlap, and outbound packets will be sent by one of the interfaces (typically the first one in the routing table). Both interfaces will be able to receive packets, but transmission will go out from one interface only.

It is possible to bypass the routing, for example the Linux "ping" command accepts a "-I" flag to specify which interface to use. This is really only intended for diagnostic/testing purposes, not for general usage. Also note that it is not sufficient to use this flag on the sender, because packet routing will occur on the receiver (which responds to ping). In the end, the reply (if any) will likely not arrive on the interface where you expect it.

So in general, each interface should be on a separate subnet. Note that subnets can be very small, such as 255.255.255.252 for example.

An old but still very much relevant guide can be found in Chapter 4 of "IP Layer Network Administration with Linux", see http://linux-ip.net/html/ch-routing.html

There are other cases in which having multiple interfaces on the same subnet makes sense - either as redundant links, or for bonding multiple links together. In these cases however, there is complex logic that determines which interface a packet takes - much more complex than a simple routing table.

shabbirk
Moderator
Moderator
119 Views
Registered: ‎12-04-2016

Hi @ajaykumar141229 

One possible method to make it work on the same subnet is to change the routing table/NAT settings.

If you want to have two interfaces on the same machine on the same subnet for redundancy/stability purposes, network bonding is another solution

 

Regards

Shabbir

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