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I understand why for IPv4 the host and the gateway should be part of the same subnet, but for IPv6 I am a little bit confused. There are several types of IPv6 address assignment, but IPv6 requires the same thing.

Is it still a must to have the gateway in the same subnet?

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  • Generally, yes. The host must be able to reach the gateway via layer 2. Since there are usually several IPv6 networks in place at the same time, only one (or two when transitioning addresses) usually have a gateway set.
    – Zac67
    Aug 20 '17 at 8:01
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin ♦
    Feb 19 '18 at 17:42
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A gateway is the host on a network that knows how to reach other networks. Your host would need a gateway just to reach a gateway on a network to which it is not directly connected.

An IPv6 host will know how to reach other hosts on any networks to which it is directly attached, but it still needs a gateway in order to reach other networks. While IPv4 uses ARP (broadcast) to resolve a layer-2 address from a layer-3 address, IPv6 uses ND (link-local multicast). Both of those protocols are confined to the local link. Each will give you the layer-2 address for a host on the same network as your host, but neither can tell your host how to route to a different network, other than pointing you to a gateway on your network.

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  • Just imagine how many routes your computer world need to know to connect to every device in the world! That's where our gateways come in.
    – Fixitrod
    Aug 20 '17 at 13:45

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