(Message mtu:3) Date: 01 Dec 1997 08:51:35 GMT From: c.c.eiftj@65.usenet.us.com (Rahul Dhesi) Newsgroups: comp.dcom.sys.cisco Subject: Re: Cannot reach sites with MTU<1500 X-Return-Path: dhesi@rahul.net X-Nojunk-Status: OK 0 Organization: a2i network References: <880958743.6326@news.Colorado.EDU> Nntp-Posting-Host: waltz.rahul.net Nntp-Posting-User: dhesi X-Comment: Encoded From: line allows replies that preserve original subject Xref: samba.rahul.net comp.dcom.sys.cisco:41014 In <880958743.6326@news.Colorado.EDU> Franck Martin writes: [ dial-up PPP, MTU 576, can't reach some web sites ] >I set the MTU to 1500 and everything went fine. Please note that I did >it at the same time as my ISP did it. >I wrote to the webmaster of these sites, and so far only one answered me >letting me know that they use a cisco local redirector. I have observed similar problems. The problematic web site always seem to be high-volume sites. And in my case too, one web site replied saying it was using the Cisco local director. My workaround was to ask users to go through a proxy server on the local network. I don't fully understand the problem. I tried tracing TCP/IP traffic and found that the offending web sites were sending a packet with the DF (don't fragment) bit set. It might be the case that the Cisco local director is trying to do MTU discovery and something is failing. -- Rahul Dhesi