Noddy question about Jumbo Frames

[PeteSmith]

Noddy question but it's irritating me so here goes.

Is there a reason why i can't or shouldn't enable jumbo frames on my home web server? I already use jumbo frames on my home workstation PC and my WHS, but every time i enable jumbo frames on my NAS, which also hosts my Wordpress blog the site will no longer load via the external IP/URL. It also prevents me from accessing any webpage hosted on the NAS (including the web management page for the NAS)

I can still access the webpages via the internal IP address and I'm still able to access the fileshares on the NAS from within my home network. The file transfer speeds do improve a little, as you might expect.

Obviously the benefit for me is accessing the files on the NAS using Jumbo frames, but i didn't expect that to interfere with the web host. Am i just missing something fundamental about jumbo frames?

[wasabi]

Does your router support jumbo frames? If not, then you'll probably only be able to access it on your own network.

[PeteSmith]

That would make sense, apparently the Virgin Media hub doesn't (or rather it wasn't configured to) so it looks like you have hit the nail on the head. Also explains why the pages load internally (via a separate switch) and bypassing the hub altogether.

[watercooled]

Going above the 'standard' 1500 MTU can cause all sorts of weirdness if a system isn't expecting to receive such packets; a compatible router would be forced to fragment the packets down into 1500 byte chunks (and reducing WAN throughput/efficiency) as the larger chunks obviously cannot pass onto the net.

However, even with a manual MTU setting, many systems will still use some form of MTU discovery; if they have trouble reaching a host with the default MTU, they'll try to negotiate a lower value, provided you're lucky enough to not have any firewalls between the two systems blocking ICMP traffic.

If you're using a Linux server, you might want to research the option

tcp_mtu_probing = 1

and check if it's enabled.

AFAIK the Superhub doesn't support jumbo frames, so is likely just dropping an packets >1500 MTU transmitted from your server, but TBH they (jumbo frames) tend to be more trouble than they're worth anyway IMHO. Check any offloading is enabled and supported; it often closes the gap with jumbo frame performance IME.