We want to implement ipv6 on our network as we begin to offer our customers dual stack. We offer dedicated servers and we wish to give a /64 with each server.

In one vlan, we wish to have 255 x /64

Is there any other way to do it on a Juniper MX router, instead of describing each gateway (255 gateways) in the configuration?

  • I'm not sure I follow. Do you want one VLAN with a /56 network (256 /64 networks)?
    – Ron Maupin
    Oct 12, 2016 at 18:17
  • @RonMaupin Yes, but split as 256x /64 (each /64 with it's own gateway)
    – VelDev
    Oct 12, 2016 at 18:20
  • Then you need that many VLANs, unless you want customers to be able to contact each other's servers at layer-2. I would think that you would want to separate the networks by layer-2, and probably firewall them from each other at layer-3.
    – Ron Maupin
    Oct 12, 2016 at 18:23
  • @RonMaupin We firewall at the switch level, it's not a problem. We need to keep the single vlan method as we already use it for ipv4. The only problem we have is that adding 1000 gateways on our router doesn't seem a clean/good solution.
    – VelDev
    Oct 12, 2016 at 19:30
  • How do you do the gateways with IPv4? It really isn't different with IPv6.
    – Ron Maupin
    Oct 12, 2016 at 19:31

1 Answer 1


A different setup would probably make more sense for IPv6. Putting multiple /64s on one layer-2 domain isn't very useful. Just one /64 has 2^64 addresses. You could let each server pick addresses from a subset of the /64 for example. If the /64 is for example 2001:db8:aa:bb::/64 then server 1 could use every address between 2001:db8:aa:bb:0001:0000:0000:0000/64 and 2001:db8:aa:bb:0001:ffff:ffff:ffff/64, etc. That way you could fit 65536 servers on a subnet with 16 million addresses per server.

But that's still pretty much IPv4-thinking. What would probably be much more useful to your customers is if you provide a routed subnet per server so that they can more easily run things like docker and virtual machines inside their server. I would recommend at least a /56 per server. If you combine this with the addressing suggestion above you could route the prefix to the ::1 address of each server. So for server 1 above you could for example set static route 2001:db8:ff00:0100::/56 to 2001:db8:aa:bb:1::1.

Then you are really using IPv6: provide plenty addresses on the LAN and give a block of subnets to each customer for virtualisation etc. Much cleaner and more useful to your customers than messing with multiple /64s on one LAN.

  • Or, a modern server may just decide to pull a RFC 7217 SLAAC address, which means you pretty much have to give it its own /64, at a minimum. This is the default in current Fedora and will probably be in a future RHEL version, for instance. Oct 13, 2016 at 2:33
  • I never enable SLAAC on server networks, I prefer server configurations to be predictable. Oct 13, 2016 at 13:06
  • They're predictable now, which is part of the point of RFC 7217. Even replacing a PCIe card NIC should not change the address. Oct 13, 2016 at 15:50
  • The addresses are more stable with RFC 7217, true. What I meant is that I don't want any auto configuration on servers. I want to manually configure the addresses they use, put them properly in DNS etc. I also have seen server networks where the admin of a server didn't think about IPv6 and never configured an IPv6 firewall etc. Especially on networks where there didn't use to be IPv6 before. That's more what I meant :) Oct 13, 2016 at 20:33
  • 2
    Aha! Since I have machines that register themselves in DNS, I don't care so much about that. The addresses only need to be reasonably stable. Oct 13, 2016 at 20:35

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