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I've just obtained a Comtrend 536+ ADSL2+ router and I've easily managed to setup a proper LAN/wifi configuration for my home machines, laptops, smartphones and such. I'm more than used to do it.

The awful thing comes when I'm using its wifi capabilities, because I've discovered that certain webpages/domains are just being blocked when connecting via wifi. On the other hand, when I browse these pages via my main desktop PC (XP), which I connect to the router via LAN, I have no problem whatsoever. So I'm basically clueless, because I've started to look for some kind of wifi/filter configuration menu inside the router's web management interface, but no luck.

One could say "probably it's your firewall/antivirus/whatever on your wifi machines the one interfering". Well, I've discarded that because it happens with a XP machine (no antivirus), but also with a Jolicloud netbook, an iTouch and an Android phone. And no matter the web-browser I use (Opera, IE, wget, telnet:80) web browsing these pages causes a time-out connection error. BTW, it's not only happening when web browsing but also with other programs, like for example Dropbox, which remains always in "connecting" state, when run on my wifi machines.

Examples of webpages working:
-ALL google services/pages/market
-www.elperiodico.com
-some FEW other...

Examples of webpages NOT working:
-facebook.com
-lavanguardia.es
-www.dropbox.com
-MANY other

I can't seem to perceive a pattern on the working/non-working pages, so I'm still clueless. I've tweaked my DNS settings (inside the router and inside my non-working devices) and no luck either. I CAN access webpages living inside my "working PC"'s apache from the "faulty" devices, but as soon as the router needs to look for webpages on the real world internet, no luck.

BTW, pinging ALL the faulty webpages/services works ALWAYS, so I would say it's not a DNS problem, as I can even see how DNS appears as properly solved when pinging.

Whenever I reconnect my old (and sometimes faulty) Amper Xavi 7768R wifi router, and with no change on the non-working devices wifi settings, EVERYTHING works seamlessly again. So it's something inside my new router which I should address.

Any hint? I don't know what to look for now...

Greetings

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This could be an MTU problem. I don't know how to tweak this on your Comtrend router, but now you have a keyword to look out for. –  Gilles Dec 12 '10 at 18:11
    
You nailed it with a hammer on the first hit. I changed the MTU value ON MY NETBOOK with TCP Optimizer, (from 1500 to 1492, as far as I remember), and now this PC has gained full connectivity via wifi. But I see this more as a workaround, as a full solution, as I can't tweak the MTU value within my iTouch/Android devices. So does anyone know how to change the MTU value of my comtrend 536+ router? (And no, I can't find the option it inside its configuration interface). I would need to add some kind of parameter somewhere inside the .conf xml file used to store internal configuration. Greetings –  Isaac Dec 13 '10 at 9:47

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