Category: IPv6

Unintended Consequences of IPv6 SLAAC

One of my friends is running a large IPv6 network and has already experienced a shortage of IPv6 neighbor cache on some of his switches. Digging deeper into the root causes, he discovered:

In my larger environments, I see significant neighbor table cache entries, especially on network segments with hosts that make many long-term connections. These hosts have 10 to 20 addresses that maintain state over days or weeks to accomplish their processes.

What’s going on? A perfect storm of numerous unrelated annoyances:

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Worth Reading: IPv6 Deployment Status

RFC 9386 documenting IPv6 deployment status in late 2022 has been published a few weeks ago1. It claims over a billion IPv6-capable users, and IPv6 deployment close to 50% in major countries.

Web content is a different story: while 40% of top-500 sites are IPv6-enabled, you can reach only ~20% of web sites over IPv6. Considering Cloudflare’s free proxying includes IPv6 that is enabled by default, that proves (once again) how slowly things change in IT.

Want to get IPv6 deployed but don’t know where to start? Check out IPv6 webinars ;)
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IPv6 Security in Layer-2 Firewalls

You can configure many firewalls to act as a router (layer-3 firewall) or as a switch bridge (layer-2 firewall). The oft-ignored detail: how does a layer-2 firewall handle ARP (or any layer-2 protocol)?

Unless you want to use static ARP tables it’s pretty obvious that a layer-2 firewall MUST propagate ARP. It would be ideal if the firewall would also enforce layer-2 security (ARP/DHCP inspection and IPv6 RA guard), but it looks like at least PAN-OS version 11.0 disagrees with that sentiment.

Straight from Layer 2 and Layer 3 Packets over a Virtual Wire:

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IPv6 Addressing on Point-to-Point Links

One of my readers sent me this question:

In your observations on IPv6 assignments, what are common point-to-point IPv6 interfaces on routers? I know it always depends, but I’m hearing /64, /112, /126 and these opinions are causing some passionate debate.

(Checks the calendar) It’s 2023, IPv6 RFC has been published almost 25 years ago, and there are still people debating this stuff and confusing those who want to deploy IPv6? No wonder we’re not getting it deployed in enterprise networks ;)

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First Steps in IPv6 Deployments

Even though IPv6 could buy its own beer (in US, let alone rest of the world), networking engineers still struggle with its deployment – one of the first questions I got in the Design Clinic was:

We have been tasked to start IPv6 planning. Can we discuss (for enterprises like us who all of the sudden want IPv6) which design paths to take?

I did my best to answer this question and describe the basics of creating an IPv6 addressing plan. For even more details, watch the IPv6 webinars (most of them at least a few years old, but nothing changed in the IPv6 world in the meantime apart from the SRv6 madness).

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Design Clinic: Small-Site IPv6 Multihoming

I decided to stop caring about IPv6 when the protocol became old enough to buy its own beer (now even in US), but its second-system effects keep coming back to haunt us. Here’s a question I got for the February 2023 Design Clinic:

How can we do IPv6 networking in a small/medium enterprise if we’re using multiple ISPs and don’t have our own IPv6 Provider Independent IPv6 allocation. I’ve brainstormed this with people far more knowledgeable than me on IPv6, and listened to IPv6 Buzz episodes discussing it, but I still can’t figure it out.

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State of LDPv6 and 6PE

One of my readers successfully deployed LDPv6 in their production network:

We are using LDPv6 since we started using MPLS with IPv6 because I was used to OSPF/OSPFv3 in dual-stack deployments, and it simply worked.

Not everyone seems to be sharing his enthusiasm:

Now some consultants tell me that they know no-one else that is using LDPv6. According to them “everyone” is using 6PE and the future of LDPv6 is not certain.

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Worth Reading: Is IPv6 Faster Than IPv4?

In a recent blog post, Donal O Duibhir claims IPv6 is faster than IPv4… 39% of the time, which at a quick glance makes as much sense as “60% of the time it works every time”. The real reason for his claim is that there was no difference between IPv4 and IPv6 in ~30% of the measurements.

Unfortunately he measured only the Wi-Fi part of the connection (until the first-hop gateway); I hope he’ll keep going and measure response times from well-connected dual-stack sites like Google’s public DNS servers.

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