Due to a ransomware attack, the wiki was reverted to a July 2022 version. . We apologize for the lack of a more recent valid backup.
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Note: “onos-app-reactive-routing” depends on “onos-app-sdnip”, so if you want to use the reactive routing function, you need to activate “onos-app-sdnip” first, and then active “onos-app-reactive-routing”.
Virtual Gateway
In legacy IP network, hosts use gateway as the default router to access the Internet. However, an SDN network uses SDN switches to connect a network rather than routers, so there is no physical gateway router in the SDN network. Without a gateway, there is an issue for hosts inside SDN network. When hosts want to communicate with other hosts in different subnetworks, they do not know the next hop where the packets should be sent. Also hosts do not know the MAC address of the next hop and can not compose the entire packet and send it out. To solve this issue, we designed a virtual gateway for SDN network.
After a host gets its gateway address, it will send out ARP packet to look for the MAC address. Since there is no physical gateway in SDN, the virtual gateway module in ONOS will take care all the ARP requests. In detail, virtual gateway module registers from ONOS for all the ARP packet-ins. It will check whether the target address in the ARP request packet is the virtual gateway address. If so, virtual gateway module will composes the ARP reply packet and send it out as packet-out to the host. Currently, we configure each gateway address together with each IP prefix in the configuration file.
Configuration
BGP Speaker Configuration
In order to announce the public prefixes to other networks, we should also configure the BGP speaker in local SDN network with all the public prefixes.
ONOS Configuration
Usually a network is assigned with several public IP prefixes. Besides those public IP prefixes, the network administrator may also want to use some private IP prefixes locally. For all those IP prefixes, we configure them in configuration file “network-cfg.json” which is located at onos/tools/package/config/network-cfg.json.
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Since "201.0.0.0/24" and "202.0.0.0/24" are public IP prefixes, you should also config them inside BGP speakers inside SDN network.
Unknown Traffic Treatment
For a destination IP address, if there is no matchable IP prefix either in sdnip.json or in BGP speaker's route table, we will install rules to drop such packets at the first hop switch where the packets come from.
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