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notfred
Member
2015-Jan-18 12:44 pm
[DSL] IPv6 Google connection hangingI'm seeing intermittent problems with IPv6 to Google. Traceroute works fine but problems opening youtube, searching or on webpages with google ads. test-ipv6.com and ipv6-test.com all work fine showing good IPv6 connectivity, so it looks like just a
I see there's a thread in direct from someone else on the same topic, but as it isn't mine then I cannot comment on it.
Anyone from TSI able to comment on what's going on? |
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 SimplePandaBSD
Premium Member
join:2003-09-22
Montreal, QC |
said by notfred:I'm seeing intermittent problems with IPv6 to Google. Traceroute works fine but problems opening youtube, searching or on webpages with google ads. test-ipv6.com and ipv6-test.com all work fine showing good IPv6 connectivity, so it looks like just a
I see there's a thread in direct from someone else on the same topic, but as it isn't mine then I cannot comment on it.
Anyone from TSI able to comment on what's going on? Phew! Exact same thing here. Intermittent random connection issues to Google via IPv6. This, of course, has repercussions Internet wide as there are problems loading things like analytics scripts, which are on A LOT of web sites and if implemented incorrectly can hang site loads. Disabling IPv6 solves the problem completely so it's purely an IPv6 issue. Started yesterday or perhaps Friday and has gotten noticeably worse leading up to today. I'm going to open a ticket in direct as well so it's made aware that there is an issue. |
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to notfred
I had been wondering what the heck has been happening with pretty much everything hosted by Google or using Google-based services for the last few days but had other stuff to do so did not bother investigating.
This would not be the first time that IPv6 stuff has gone screwy. |
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Edward_KAs old as the dot com boom
join:2000-09-14
CANADA |
to notfred
IPv6 PMTUD to Google broken; I had to add a rule to clamp MSS to Google IPv6 netblocks. Assuming your MTU is 1492 and you use RouterOS, see attachment. (MTU - 20 - 40 = 1432 MSS) My TS Direct post: » [IPv6] IPv6 Google connection hangs |
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SimplePandaBSD
Premium Member
join:2003-09-22
Montreal, QC |
to notfred
Interesting. Are you noticing this as relatively new behaviour? It seems I wasn't having any issues to Google as early as mid week this week. |
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Edward_KAs old as the dot com boom
join:2000-09-14
CANADA |
Something changed in the last week or so, was driving me crazy. Thought I was going crazy when it sometimes works or doesn't work; possibly mixing up with the slow speeds thread (» [Cable] Slow speeds) so I waited it out until it became unbearable and clearly not the same issue. |
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SimplePandaBSD
Premium Member
join:2003-09-22
Montreal, QC |
Yuck.
IOS 15.0, which I'm running at home right now, lacks "ipv6 tcp adjust-mss". Apparently in 15.2 the standard "ip tcp adjust-mss" will apply to any IPv6 packets on the same interface but, alas, this means I have to do a firmware upgrade for this router. Sigh.
TSI hasn't responded to my thread in direct yet; any chance they indicated to you they'd be applying any fixes on their side? |
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Edward_KAs old as the dot com boom
join:2000-09-14
CANADA |
"Tier2 team" is looking at it. So... no fixes yet.
Uhh, add a poison route for Google IPv6? Hopefully you can survive by falling back to Google IPv4. (2607:f8b0::/32) |
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to notfred
FYI there have been complaints on HE's forum as well. I've been mss clamping for a while now so I never saw any issues |
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SimplePandaBSD
Premium Member
join:2003-09-22
Montreal, QC |
said by JAMESMTL:FYI there have been complaints on HE's forum as well. I've been mss clamping for a while now so I never saw any issues About Google specifically? FYI all I just got the same back from TSI support: escalated to tier 2. Well, at least this gives me an excuse to stop being lazy and update this router.  |
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JAMESMTL
Premium Member
2015-Jan-18 4:14 pm
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 Gone
Premium Member
join:2011-01-24
Fort Erie, ON |
to notfred
Hah, I wondered what the heck was going on. |
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chrisA
join:2012-08-23
Hamilton, ON
1 edit |
to notfred
Noticed this issue on Friday, still a problem as of Monday morning.
Edit: IPv6 to Google is working at one location, but not the other, both DSL. |
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SimplePandaBSD
Premium Member
join:2003-09-22
Montreal, QC |
said by chrisA:Noticed this issue on Friday, still a problem as of Monday morning.
Edit: IPv6 to Google is working at one location, but not the other, both DSL. What kind of CPE at different locations? Seems the solution is an MSS clamp so you may be (even inadvertently) doing so in one location and not another. |
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chrisA
join:2012-08-23
Hamilton, ON |
chrisA
Member
2015-Jan-19 10:52 am
It's a very basic setup at both locations. Auto configuration on a Linksys ea3500 on 6/0.8 ADSL, and Auto configuration on a SmartRg on 25/10 VDSL.
Both connections had this issue at some point this weekend, but the problem with the slower connection resolved itself, and the problem with the faster connection is still ongoing.
I've made no configuration changes other than enabling/disabling IPv6 a couple times while troubleshooting. |
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to Edward_K
Thanks for this!
I applied a stub rule to my pf firewall setting the max MSS and this fixed it.
I had been annoyed for several days now with YouTube.com and Google.
However, the pf article I found recommended a max MSS of 1436. I used that and all seems fine. |
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SimplePandaBSD
Premium Member
join:2003-09-22
Montreal, QC |
1432 should be correct (1492 layer 2 MTU - 40 byte IPv6 header - 20 byte TCP header) = maximum size of a TCP segment payload. |
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SimplePanda
2 edits |
to notfred
FYI for Cisco users: # conf term
(config)# interface dialer 1
(config-if)# ip tcp adjust-mss 1432
If you're using 15.2(4)M or later this will ALSO clamp IPv6 encapsulated TCP packets at the same size as their IPv4 counterparts, despite not being an "ipv6" command. Ideally it'd be -20 bytes for IPv6 but this is the way it goes until a full "ipv6 tcp adjust-mss" command is implemented. I've also verified the mss is 1432 regardless of protocol using tcpdump: IP6 MY-MACHINE-HERE.54911 > MY-SERVER-HEREssh: Flags [S], seq 147644298, win 65535, options [mss 1432,nop,wscale 5,nop,nop,TS val 924963438 ecr 0,sackOK,eol], length 0
Incidentally, "ipv6 tcp adjust-mss" is already in current versions of IOS XE. Hopefully this trickles down to standard IOS at some point so we can keep 1452 for IPv4 and 1432 for IPv6. You can tell it's working thusly: #show ipv6 interface dialer 1
Dialer1 is up, line protocol is up
-snip-
Input features: Dialer i/f override IPv6 TCP Adjust MSS
Output features: IPv6 TCP Adjust MSS Dialer idle reset
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1 edit |
Been busy the past few days and didn't get a chance to throw the MSS clamp in my ip6tables rules, I was going to do it last night when I noticed Google now seems to be working again.
I'm going to throw MSS clamp rules in for IPv4 and IPv6 anyway as that should improve latency on the first connection. |
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SimplePandaBSD
Premium Member
join:2003-09-22
Montreal, QC |
Seeing routing and/or GeoDNS changes for Google hostnames so either Google or TSI may be making some changes to address this issue.
Doing the same as you; just going to leave clamping in place. |
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