IPv6 Facebook issues ?

Forums › New Zealand Broadband › IPv6 Facebook issues ?

xpd

Geek of Coastguard
14115 posts

Uber Geek
+1 received by user: 4574

Retired Mod

ID Verified

Trusted

Lifetime subscriber

#321558 29-Aug-2025 08:44

Over last couple of years, I've noticed that whenever I visit Facebook.com, it seems to stall loading, and if it does load, it rarely seems to load the entire page/content - I'll get 2/3'rds of feeds and then stall and sit there spinning.

Can do the same with Messenger chats, someone will message me, I'll load up the browser, click on the messenger logo and it sits there....

Now, this has occurred on multiple systems, multiple ISP's, multiple routers, browsers, with and without adblocks etc. So its not an ISP or local issue as such. The only two things Ive found in common are : IPv6 and Facebook.

Turn off IPv6, and it seems to behave.

Mobile devices seem to behave. (App on iOS and Android)

Is this just me by some weird miracle or have others experienced it ?

XPD / Gavin

LinkTree

freitasm

BDFL - Memuneh
80646 posts

Uber Geek
+1 received by user: 41029

Administrator

ID Verified

Trusted

Geekzone

Lifetime subscriber

#3408396 29-Aug-2025 08:47

Never had this problem. Are you sure you don't have some weird DNS configuration that you replicate across even when moving providers?

Referral links: Quic Broadband (free setup code: R587125ERQ6VE) | Samsung | AliExpress | Wise | Sharesies

Support Geekzone by subscribing (browse ads-free), or making a one-off or recurring donation through PressPatron.

KiwiSurfer

1722 posts

Uber Geek
+1 received by user: 993

ID Verified

Lifetime subscriber

#3408490 29-Aug-2025 12:03

I've obseved Facebook.com not loading posts a few times but haven't pinpointed it to IPv6 -- I thought it was just Facebook being buggy! I did also wonder if it was my Firefox extenstions causing issues.

Next time I observe this on my home IPv6 I'll do a some digging. I do realise now my work IPv4-only connection doesn't have much issues with loading Facebook desptie similar Firefox extenstions to my home computers.

However Messenger.com has worked fine for me generally (although to be fair 90% of my Messenger usage is app-based).

Interesting to note I've not had any issues with the apps on any connection -- just Facebook web seems to be flakey for me.

muppet

2642 posts

Uber Geek
+1 received by user: 1660

Trusted

#3408529 29-Aug-2025 14:04

v6 with Mecury here, no issues loading any Meta estate assets.

Keep a ping going to 2600:: (not Meta)

Does it stay rock solid?

KiwiSurfer

1722 posts

Uber Geek
+1 received by user: 993

ID Verified

Lifetime subscriber

#3408590 29-Aug-2025 14:50

I suspect it's not something that a simple ping will surface the issue. My obs is that the Facebook.com website will load fine, it's just the posts sometimes won't load so you end up with the FB UI working fine generally except that there are no posts in the feed area (or as OP says sometimes it will show some posts but not load any more). Suspect there's a API call that's supposed to retrieve the posts failing -- but not sure why it would only fail on IPv6 though. Generally other stuff on the Facebook website works fine -- it's generally just loading the feed that is probematic.

MichaelNZ

1594 posts

Uber Geek
+1 received by user: 485

Trusted

Net Trust Ltd

#3408670 29-Aug-2025 19:47

We peer IPv4 and IPv6 with Meta so they definitely support it.

I have IPv6 to my desktop and it works fine.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers | ZL2NET

fe31nz

1294 posts

Uber Geek
+1 received by user: 423

#3408704 29-Aug-2025 23:30

xpd:

Over last couple of years, I've noticed that whenever I visit Facebook.com, it seems to stall loading, and if it does load, it rarely seems to load the entire page/content - I'll get 2/3'rds of feeds and then stall and sit there spinning.

Can do the same with Messenger chats, someone will message me, I'll load up the browser, click on the messenger logo and it sits there....

Now, this has occurred on multiple systems, multiple ISP's, multiple routers, browsers, with and without adblocks etc. So its not an ISP or local issue as such. The only two things Ive found in common are : IPv6 and Facebook.

Turn off IPv6, and it seems to behave.

Mobile devices seem to behave. (App on iOS and Android)

Is this just me by some weird miracle or have others experienced it ?

This is a well known problem. Facebook's front page sends lots of data using full length TCP packets. When IPv6 over PPP is incorrectly configured, these long packets get dropped by the PPP connection as being too long. With IPv4, the long packets will automatically be fragmented into smaller packets that fit the maximum size of the PPP connection. IPv6 does not allow fragmentation of packets except at the source device, hence the over long IPv6 packets just get dropped. The problem is that all the PPP software I have met disobeys a fundamental rule of IPv6 - when it drops an over long IPv6 packet, there is a requirement for an ICMPv6 "packet too long" reply to be sent back to the sender. That reply carries the maximum packet size that will fit. The sender will see that reply and then reduce the packet size and re-send the data. So in fact the PPP software is broken, and you have to work around this problem as no-one seems to be going to fix it.

The reason that PPP connections have problems with long packets is that the PPP protocol adds an extra 8 bytes to the packet headers. The normal maximum packet size (MTU = Maximum Transmission Unit) on Ethernet for IP packets is 1500 bytes. On Ethernet, there are Ethernet headers and checksums as well outside the IP packet, but when the IP packet is sent over the Internet, just the IP packet bit of up to 1500 bytes gets sent. A lot of Internet connections are done using MTU 1500 packets, but not all, as the packet may have to pass through a connection somewhere that uses another or an additional protocol. If that protocol adds extra headers to do its job, then the extra headers can be outside the IP packet or inside the IP packet. If they are outside, then the physical connection has to allow for the extra bytes, so if say 10 extra bytes are added, the connection needs to be able to handle 1510 byte packets, but the IP packet itself does not notice this. If the extra header bytes are inside the IP packet, as they are for PPP, then there are two options - either the MTU allowed for the original IP packet before adding the headers has to be smaller to allow for the extra header bytes, or the MTU allowed for the IP packet on the PPP connection after the extra header bytes have been added has be be increased to allow for the extra header bytes. So for PPP to pass an full length IP packet of 1500 bytes, the MTU of the connection PPP runs over needs to be 1508. If that is not possible, then the size of the IP packets arriving at the PPP connection needs to be limited to MTU 1500-8=1492.

In New Zealand, the fibre providers all understand this problem and provide the ability to send MTU 1508 packets over the fibre network, so that the MTU of connections carrying PPP on fibre can be set to 1508. This is called "overprovision". However, making this work relies on the ISP also allowing MTU 1508 for PPP connections, and your router also allowing PPP connections to use MTU 1508. The PPP software also needs to allow and negotiate for MTU 1508, which it has now done for a long time. So if you are connecting to your ISP via PPP, make sure to set your router so the WAN connection MTU is 1508, any VLAN 10 connection (if used) is also MTU 1508, and the PPP connection is set to MTU 1500. If your router is unable to do this, get a better router! If you want to keep using the existing router, you need to set the PPP MTU to 1492 (which will affect IPv4 and IPv6), or tell your router to add an MTU 1492 limit in the IPv6 Router Advertisement (RA) packets that it sends out to configure IPv6 on things connected to it. Similarly, if your ISP does not support MTU 1508, change to an ISP that knows and cares about doing IPv6 properly and does support MTU 1508. Or change your router settings as above.

Or if your ISP supports it, you can change to using DHCP for the connection, as that works with MTU 1500. But be aware that if something goes wrong with a DHCP negotiated connection, it can take much longer to recover from the problem than with PPP. PPP normally recovers a connection within a second or two of the problem going away - DHCP can take many minutes, depending on how it is configured.

BTW The reason that mobile devices work and PC browsers do not is likely just that the mobile version of Facebook's front page sends shorter packets. But whenever a long IPv6 packet does get sent to the mobile device via a PPP connection, it will go missing and that will cause subtle or not so subtle problems.

Lego

Shop now for Lego sets and other gifts (affiliate link).

xpd

Geek of Coastguard
14115 posts

Uber Geek
+1 received by user: 4574

Retired Mod

ID Verified

Trusted

Lifetime subscriber

#3410285 2-Sep-2025 10:11

Did some more poking around, and found its fbcdn.net thats stalling all the time. Did some poking around in relation to that and found masses of posts with the same issue.

Appears its primarily Fx browser based issue, where they're enabling "https3". Turn it off, issue goes away. But, some as with myself, found the issue was present regardless which browser.

So in Fx, I used this command : network.http.http3.enable and set it to disable.

Problem has gone away, and images etc load WAY faster on Facebook. So I'm a happy FB camper for now.

XPD / Gavin

LinkTree

NickMack

977 posts

Ultimate Geek
+1 received by user: 831

Trusted

In memoriam

Lifetime subscriber

#3410287 2-Sep-2025 10:15

xpd:

Did some more poking around, and found its fbcdn.net thats stalling all the time. Did some poking around in relation to that and found masses of posts with the same issue.

Appears its primarily Fx browser based issue, where they're enabling "https3". Turn it off, issue goes away. But, some as with myself, found the issue was present regardless which browser.

So in Fx, I used this command : network.http.http3.enable and set it to disable.

Problem has gone away, and images etc load WAY faster on Facebook. So I'm a happy FB camper for now.

Facebook is dead, bring back IRC :-) Bring Your Ideas to Life with Base44

https://nick.mackechnie.co.nz | NZ ISP latency monitoring - https://smokeping.thenet.gen.nz

xpd

Geek of Coastguard
14115 posts

Uber Geek
+1 received by user: 4574

Retired Mod

ID Verified

Trusted

Lifetime subscriber

#3410385 2-Sep-2025 10:38

NickMack:

xpd:

Did some more poking around, and found its fbcdn.net thats stalling all the time. Did some poking around in relation to that and found masses of posts with the same issue.

Appears its primarily Fx browser based issue, where they're enabling "https3". Turn it off, issue goes away. But, some as with myself, found the issue was present regardless which browser.

So in Fx, I used this command : network.http.http3.enable and set it to disable.

Problem has gone away, and images etc load WAY faster on Facebook. So I'm a happy FB camper for now.

Facebook is dead, bring back IRC :-) Bring Your Ideas to Life with Base44

Nah, bring back the BBS with multi-node chat :D

XPD / Gavin

LinkTree