Results 1 to 5 of 5

Thread: DNS lookups fail with jumbo frames

  1. #1
    Join Date
    Apr 2005
    Location
    Providence, RI
    Posts
    484

    DNS lookups fail with jumbo frames

    I recently upgraded my network adapters to the AGIGAUSB 10/100/1000. Two DTivos, both running 6.2a. I enabled jumbo frames on each (size=8972) and they're both plugged into a Linksys RVS4000 router (the ports on the router have also been set correctly). I can ping with jumbo frames, and Tivo to Tivo transfers have greatly increased in speed (I did a before/after with netperf.) So far, so good. Now, however, I can't get outside my intranet. Anything like wget gives a " Host name lookup failure". I'm using DHCP, and have resolve.conf set correctly in /etc. Also, if I reboot with regular-size frames everything works fine. Anyone know what I'm missing?

    ***EDIT*** adding a 'route gw' to my router fixed it. If anyone wants to explain why I didn't need it before but did after I changed the frame size, please I'm all ears...
    Last edited by djl; 02-03-2009 at 12:17 PM.
    More software at http://davidlauria.com/software.
    The lost alt-rock masterpiece from the '90s, Range of Motion's "Soft Buzz of Silence", is now available on iTunes!

  2. #2
    Join Date
    Jul 2005
    Posts
    504
    I will only try to guess that there is a bug in the RVS4000 firmware where it isn't adjusting the MTU?
    Was your DNS server set to the router itself which handled the requests or were the TiVos directly accessing the DNS servers on the internet?

  3. #3
    Join Date
    Apr 2005
    Location
    Providence, RI
    Posts
    484
    The Tivos are set to access the DNS servers on the internet. I would have no problem believing there's a bug in the router; it is the single buggiest piece of equipment I've ever bought.
    Anyway, since I set up the route all is well. Gig transfers were well worth the trouble.

    Quote Originally Posted by ciper View Post
    I will only try to guess that there is a bug in the RVS4000 firmware where it isn't adjusting the MTU?
    Was your DNS server set to the router itself which handled the requests or were the TiVos directly accessing the DNS servers on the internet?
    More software at http://davidlauria.com/software.
    The lost alt-rock masterpiece from the '90s, Range of Motion's "Soft Buzz of Silence", is now available on iTunes!

  4. #4
    Join Date
    Mar 2007
    Location
    Atlanta, GA
    Posts
    72

    DNS large packets?

    DNS queries use UDP and are typically less then 512 bytes per packet, so I'm not sure how changing to jumbo frames by itself affect lookups.

    If it was still broken, or you're just curious, I'd say to capture some queries and responses from the network before and after changing the jumbo settings.
    Probably not worth the time, since its working again.

  5. #5
    Join Date
    Jul 2005
    Posts
    504
    I would be curious to look over a sniff of yours if you do have the itch to test.

    Wireshark is still free for pretty much every popular OS

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •