Comodo download via IPV6 fails

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There should be no need to manually change the MTU on the PC, providing your router is sending correct IPv6 router advertisements.

By setting both WAN and LAN MTU to 1492 I am able to browse to help.comodo.com and download from downloads.comodo.com using ipv6!!

Are you getting a ‘packet too big’ when making connections to these sites over IPv6?

So it seems to me that LAN MTU should be less than or equal to WAN MTU, in order for help.comodo.com etc to work.

There shouldn’t be any differences between the MTU sizes, on the router and any device on you LAN that uses IPv6.

My questions are: 1.Why I don't face the same problem with ipv4? WAN MTU is 1492, LAN MTU for ipv4 remains 1500 but i can browse to help.comodo.com via ipv4 just perfect.

IPv6 and IPv4 are handled differently with regard to fragmentation. IPv4 packets can be fragmented by any router they pass through. If fragmentation occurs,it’s up to the participants to perform reassembly. With IPv6 fragmentation is not performed by routers. If an IPv6 packet is received that is too large to forward, it’s dropped. Because of this, it’s up to the participants to determine the largest size for packet transfer.

2.Why I don't face the same problem with other Ipv6 enabled sites, like facebook. They continue to work when WAN MTU is set to 1492 and LAN interface to 1500 (Which is Windows default setting).

Any ideas?

This is the question we’re trying to answer. Ronny seems able to connect, where as I cannot, yet we both use the same tunnel broker.

@Ronny. Have you changed the advanced tunnel options (MTU size) on your HE configuration page

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Only during troubleshooting, currently Tunnel Broker is set to 1480 and Tunnel0 interface on my router also to 1480, Vlan1 has ipv6 mtu 1480 so that get’s router advertised to my Win7 system.

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Those settings are the same as my configuration, which works everywhere - that I know of - apart from the two comodo sites. The only way I can get these sites to function, with IPv6, is by setting my router MTU and hence the PC MTU, Basically to 1280. Basically PMTUD is failing on these sites.

44

Hi folks,

well, i’d like to inform you that this bug is actually in progress:

I’m able to tracert the site http://downloads.comodo.com using IPv6 but all sites keep to be blank or deny finding anything (no error-post). No downloads of anything (clientinstaller.exe and AV-Databases, even the popup-commercials keep to be blank) were possible.

If switched back to IPv4 everything works like a charm.

Could you please investigate this further?