nanog mailing list archives

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From: Jon Lewis via NANOG <nanog () lists nanog org>
Date: Thu, 17 Apr 2025 16:50:43 -0400 (EDT)

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On Thu, 10 Oct 2024, Andrew Peterson via NANOG wrote:

From what I've seen, rolling out dual-stack will take about 40% of your traffic to native v6. YMMV of course.

More like 10% here.

With respect to the port usage, I've seen some CGN solutions that pre-allocate a block of ports per inside IP, but allow 
overflow, so they will allocate additional blocks of ports as needed. That seems to be a good balance because you don't burn a 
ton of ports for lighter users, and the logging requirements are pretty minimal since a log only gets generated when an additional 
block is allocated. It does mean that one user's traffic could be popping out of two different public IPs.

Juniper does support overflow, but IIRC, in a later release than we're currently running, and the overflow requires a separate dedicated overflow pool. We already had to move from a single pool to seven to solve the IP

Geo problem "one big pool" had caused. Configuring overflow pools without breaking IP Geo [again] would mean doubling the number of pools (one overflow pool for each regional pool). While not technically un-doable, it's not something I want to add to our config...not to mention, it means "stealing" some IP/port resources from the existing pools or adding additional IPs. As you mention, I also have unanswered questions about how well it plays, if at all, with address pooling paired. Theoretically, it could still work, since Junos will let you configure the overflow pool using the same IPs as the main pool, splitting the IPs between pools by each pool using different port ranges.

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Current thread:

• [NANOG] Re: CGNAT growing pains Jon Lewis via NANOG (Apr 17)
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  • [NANOG] Re: CGNAT growing pains Jon Lewis via NANOG (Apr 17)