LLigetfa
join:2006-05-15
Fort Frances, ON | reply to inova
Re: Won't pass traffic
What are you running for MTU? |
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inova
join:2006-05-03
Macnutt, SK
edit:
May 7th, @06:03PM
| Would you believe, uh, 300? Nice catch! I set it back to 1492 and bingo! I can't explain the mtu being set to 300. I had reset the cpe to factory defaults and loaded a basic config I use to start with. I don't mess with mtu settings, I leave them at default.
I am impressed LLigetfa. There is quite a bit of stuff comes up on a google search of "page cannot be displayed". In all of my reading I don't recall anyone suggesting mtu settings. What made you think of it?
Vista still sucks though... |
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LLigetfa
join:2006-05-15
Fort Frances, ON
| said by inova  :What made you think of it? Ummm... well... it sounded like an MTU problem. 
Often though MTU might be set higher and only some sites don't work.
Also, it depends on whether PMTUD is enabled in the OS and if the router supports it.
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Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it. -- Stephen Vizinczey |
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inova
join:2006-05-03
Macnutt, SK
| said by LLigetfa :Often though MTU might be set higher and only some sites don't work. I have come across this a couple times with government sites and changed the mtu at the cpe and the problem went away. Is this something that should be adjusted at my head end router to effect global changes? Or should all devices be set the same? |
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LLigetfa
join:2006-05-15
Fort Frances, ON
| It depends on how the network is setup. 1492 is only common if you are doing PPPoE, 1500 otherwise. You should run MTU of 1500 where there is PPPoE packets tunneling through. 1492 only if the CPE is using PPPoE to your LNS. If the client router is doing the PPPoE, then the CPE should be 1500 and the client router should be 1492.
PMTUD usually works but needs ICMP and some overzealous admins will disable it. Also, Microsoft decided PMTUD is a security risk and may disable it too. In reality PMTUD is sometimes used as a DoS and is not a *real* security risk.
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Strange as it seems, no amount of learning can cure stupidity, and formal education positively fortifies it. -- Stephen Vizinczey |
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hattmardy
join:2007-01-23
Atlanta, GA | I have also seen MTU issues where images and certain websites would not show up ... but wow 300, that's low!  |
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