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Method for avoiding ARP in a cloud network Disclosure Number: IPCOM000248946D
Publication Date: 2017-Jan-24
Document File: 7 page(s) / 36K

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In a cloud network using IPv4 over ethernet, configuring the MAC (Media Access Control) address of VRs(Virtual Routers) and VMs(Virtual Machines) to a value calculated from their IP(Internet Protocol) address. So that when communicating in such network, the destination MAC address can be calculated out from the destination IP address through the same algorithm instead of learning it through ARP protocol or look it up in static ARP tables.

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Method for avoiding ARP in a cloud network

1. Background

Computer network is the most important and basic infrastructure of IT systems, and IPv4(Internet Protocol Version 4) over Ethernet

is the most widely used protocol in modern computer network. In the scenario of IPv4 over Ethernet communication, the whole

network is divided into network segments, and computer hosts are divided into groups that are "placed" into these segments.

When a host wants to send a data packet to another host in the same network segment, it needs to

a. Get the MAC address of the destination

b. Write it into the destination MAC field of the packet

c. Hand the packet to the layer-2 forwarding device, e.g. ethernet switch.

Then the layer-2 forwarding device will transmit the packet to the destination host according to the destination MAC address in the


When a host wants to send a data packet to another host in other network segments, it needs to

a. Get the MAC address of the layer-3 forwarding device

b. Write it into the destination MAC field of the packet

c. Let the layer-2 forwarding device transmit it to the layer-3 forwarding device, e.g. IP routers.

Then the layer-3 forwarding device will route the packet to the destination network segment according to the destination IP address

of the packet.


From the above we can see that the sender needs to learn a MAC(Media Access Control) address, no matter it belongs to the

destination host or the layer-3 forwarding device, before it can send out a communication packet. Traditionally, this is done by the

ARP(Address Resolution Protocol, RFC(Request For Comments)826, Internet Standard STD37). The sender broadcasts an ARP

request to all the hosts in the same network segment to ask for the MAC address of a particular IP host. Then the host that has the

IP replies with an ARP response containing it's MAC address to the sender. Also, a host can broadcast a ARP packet proactively to

advertise it's IP and MAC address to every host in the same network segment. This is called Gratuitous ARP.

2. Problems

The ARP approach has the following problems:

a. Security problem. With ARP approach, it relies on the "honesty" of every host in the network segment when doing the ARP

transaction to make the network work properly. Many malicious techniques and software have been developed to attack the

network through ARP. The examples of ARP attack techniques include ARP spoofing, ARP cache poisoning, or ARP poison routing.

b. Performance problem. The ARP requests and Gratuitous ARP are transmitted as broadcast. Broadcast traffic is very bandwidth

consuming and harmful to network performance, especially when the network segment spans large on physical topology, which is

very common case in cloud computing environments.

c. Reliability problem. Because broadcast traffic often cause network problem we usually want to disable broadcast totally to

improve reliability. This requirement is more vital to a large layer-2 network, which are usual...