Member Avatar for tuxxy

Any help at all will be appreciated. After configuring my wireless d-link DI 524 I can surf the net but i cannot open my hotmail! through my modem (wired) no problems.

  • 2 Contributors
  • 2 Replies
  • 99 Views
  • 2 Days Discussion Span
  • Latest Post Latest Post by tuxxy

Dani AI

Generated

Quick take: this is a classic MTU/fragmentation problem that can break some HTTPS/webmail sessions when going through a router but not when connected directly to the modem. Good catch by — the underlying cause is that large packets are being dropped because the sender is not being told to shrink them (Path MTU Discovery relies on ICMP "fragmentation needed" messages). See the protocol explanation for details RFC 1191 and a practical overview at Path MTU Discovery.

Practical checks you can run right now:

  • Use ping with the "do not fragment" option to discover the largest payload that gets through. On Windows: 
    ping -f -l 1472 example.com

    reduce the size until the ping succeeds; add 28 bytes to that payload to compute the MTU. On Linux use ping -M do -s.

  • Check whether your ISP uses PPPoE or similar (these add header overhead and reduce usable MTU) — see PPPoE.
  • In the router GUI look for MTU, MSS clamping, or any "block ICMP/WAN ping" settings. Either set an appropriate MTU, enable MSS clamping, or allow the specific ICMP type needed for PMTU. Update router firmware before making permanent changes.

Cautions: lowering MTU can affect VPNs or other services, so test broadly after changes. If unsure, capture your MTU test values and router firmware version and share them with ISP or vendor support for a targeted fix.

Recommended Answers

All 2 Replies

Member Avatar for jimlaver

Check the MTU value. Change it to 1420.

Good luck.

Member Avatar for tuxxy

it works! thanks mate.
thank god for forums (sooo, this is how forums are helpful...i like it!)

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.