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0 pointsneilalexander4y ago0 comments

How switches "handle" multicast is not a new problem — many will treat it as broadcast traffic and flood it across the network segment, leaving clients to work out if they are interested or not. More intelligent switches might perform IGMP snooping to avoid flooding and this will be no more complex with IPv6 than it is with IPv4 today.

Multihoming also isn't new and isn't really IPv6-specific. It might be more likely that you'll have multiple IPv6 prefixes but the majority of source address selection rules that you are used to in IPv4 will still apply, and you might have already ran into these problems in the IPv4 world if you have multiple network interfaces anyway.

Subnetting is probably not easier or harder. The address length doesn't change how subnetting or how routing tables work and I am not really convinced that an IPv6 addressing plan should really be any worse or better than an IPv4 addressing plan. The minimum prefix size of /64 for a network segment is about the only extra consideration there, but if anything, it should be simpler than having to manage globally routable address space and private address space separately given that you can now manage address space as a true single hierarchy.

You're right that SLAAC vs DHCP can add a bit of mental overhead, but for most configurations, configuring DHCP and letting RAs be sent automatically in IPv6 is not much different to configuring a default gateway in DHCP on an IPv4 network.

Finally, as for ICMPv6, it has always been bad behaviour to just outright filter ICMP without consideration for what it will break. The stakes are indeed higher than in IPv4, but it seems worth it if we can eliminate two entirely separate protocols in the process and firewall vendors and admins are just going to have to learn that.

I get there are a lot of cognitive factors involved in why people resist IPv6 but it really isn't as alien as most people think and most of the concerns are easily answered.

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pilif4y ago

> many will treat it as broadcast traffic and flood it across the network segment

and some will silently swallow them until you update their firmware. Broadcasts on the other hand are so common (and required for ipv4 to work) that they are rarely broken.

If multicast is treated as broadcast, stuff works "fine", but because of IGMP snooping and additional "intelligence" the switches often employ, unfortunately, the failure modes I have seen tend to be packet loss rather than overeager packet forwarding.

And with multicast packets dropped in a v4 network, some niche applications will stop working, but with multicasts packets dropped in a v6 network, your network will stop working. Period.

> and you might have already ran into these problems in the IPv4 world if you have multiple network interfaces anyway

of course you have. My point isn't that v6 multi-homing is any different from v4 multi-homing. My point is that multi-homing is rare with v4 but very common and required for v6. So what's often not an issue at all on anybodies radar in a v4 network is something everybody has to deal with in a v6 network.

> most of the problems can be trivially solved.

absolutely. But they don't have to be solved by staying with v4 and thus inertia is even harder to overcome than it normally is. That was my point.

icehawk4y ago

> of course you have. My point isn't that v6 multi-homing is any different from v4 multi-homing. My point is that multi-homing is rare with v4 but very common and required for v6. So what's often not an issue at all on anybodies radar in a v4 network is something everybody has to deal with in a v6 network.

Multi-homing (connecting to multiple different networks) isn't required in IPv6 at all. Having multiple different addresses on the same subnet isn't multi-homing, and the link local address of fe80:: isn't a different network. Operating systems won't even use the link local address to establish a connection unless specifically forced to.

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