The Ipv4 Address Swamp: the New Normal
Key topics
The debate around IPv6 adoption and its impact on routing tables is heating up, with commenters weighing in on whether the new protocol will simplify or complicate the issue. Some argue that IPv6 won't necessarily reduce the number of routes, as organizations may still advertise multiple prefixes, while others point out that a single IPv6 prefix is computationally easier on routers than multiple IPv4 prefixes. The discussion reveals a nuanced understanding of the complexities involved, with insights into the role of Content Addressable Memory (CAM) in core infrastructure routers and the impact of IPv4 address scarcity on prefix allocation. As the internet continues to evolve, this conversation highlights the ongoing challenges and trade-offs in managing the ever-growing routing table.
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6h
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Based on 18 loaded comments
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- 01Story posted
Dec 23, 2025 at 11:11 AM EST
11 days ago
Step 01 - 02First comment
Dec 23, 2025 at 5:12 PM EST
6h after posting
Step 02 - 03Peak activity
9 comments in 24-36h
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Step 03 - 04Latest activity
Dec 29, 2025 at 12:27 PM EST
5d ago
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I mean a million is objectively a large number if it's all on paper, but to me, that's not a particularly large data set for talking about the entire freaking internet.
And how cheap of a SOC can handle that in memory? A better question might be to even make a system on a chip that couldn't handle that memory?
Since we don't have time machines probably the best solution is to refuse prefix portability.
On the IPv6 side; by 2002, nobody was really experimenting with A6 records any more, and EUI64 was needless. Both were parts of IPv6 designed to facilitate "easy" renumbering, so that single prefixes could be replaced with larger ones. But the ISPs weren't complaining any more about table size.
Routers had to get better (more tcam capacity) because there wasn't much choice. Nobody wants to run two border routers each with the table for half the /8s or something terrible like that.
My small hosting provider has I think 7 v4 prefixes, but could be one v6 prefix. Maybe not --- a lot of their /22s are advertised as four /24s to allow for a DDoS Mitigation provider to attract traffic when needed; but it'd probably still be fewer prefixes with v6.
Not every ASN looks the same, but many of them would advertise a lot fewer prefixes if they could get contiguous addresses, but it's not possible/reasonable to get contiguous allocations for v4.
Since the routing table is organized around prefixes, if there is complete migration, the routing table will probably be smaller.
The really valuable prefixes are those with are stable and have good reputation on them.. Everything else is junk these days..
>IPv6 would only promote incautious distribution which would again result in address space exhaustion
There are more ipv6 addresses than there are atoms in the earth.
>more abuse and increased cybercrime.
IP address-based mitigations are already not effective with v4, can you talk about why v6 makes this worse?