Ipv4 Multinetting; Multinetting Topology - Extreme Networks ExtremeWare XOS Guide Manual

IPv4 Multinetting

IP multinetting refers to having multiple IP networks on the same bridging domain (or VLAN). The
hosts connected to the same physical segment can belong to any one of the networks, so multiple
subnets can overlap onto the same physical segment. Any routing between the hosts in different
networks is done through the interface of the router. Typically, different IP networks will be on different
physical segments, but IP multinetting does not require this.
Multinetting can be a critical element in a transition strategy, allowing a legacy assignment of IP
addresses to coexist with newly configured hosts. However, because of the additional constraints
introduced in troubleshooting and bandwidth, Extreme Networks recommends that you use
multinetting as a transitional tactic only, and not as a long-term network design strategy.
Multinetting was not supported in ExtremeWare XOS 10.1, but versions of ExtremeWare prior to that
supported a multinetting implementation that required separate VLANs for each IP network. The
implementation introduced in ExtremeWare XOS 11.0 is simpler to configure, does not require that you
create a dummy multinetting protocol, and does not require that you create VLANs for each IP
network. This implementation does not require you to explicitly enable IP multinetting. Multinetting is
automatically enabled when a secondary IP address is assigned to a VLAN.
The following sections discuss these multinetting topics:
Multinetting Topology on page 503
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How Multinetting Affects Other Features on page 504
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Configuring IPv4 Multinetting on page 508
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IP Multinetting Examples on page 509
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Multinetting Topology

For an IP multinetted interface, one of the IP networks on the interface acts as the transit network for
the traffic that is routed by this interface. The transit network is the primary subnet for the interface.
The remaining multinetted subnets, called the secondary subnets, must be stub networks. This
restriction is required because it is not possible to associate the source of the incoming routed traffic to a
particular network. IP routing happens between the different subnets of the same VLAN (one arm
routing) and also between subnets of different VLANs.
ExtremeWare XOS 11.3 Concepts Guide
IPv4 Multinetting
503