?
Solved

Cannot access certain websites...

Posted on 2004-11-17
3
Medium Priority
?
380 Views
Last Modified: 2010-04-17
Ok, I have read and read and read and researched and not found a damn thing!!!  I am sure it is something simple but anyways, here's the problem.

I cannot seem to get to yahoo.com, romeoville.org and a few other selected sites.  I just chalked it up to the sites bouncing, but have dropped that theory since I can remote to my home computer and get on the sites with no problem.  I can go into my firewall here at work and ping each site without a problem, I can go into the INTERNET router and ping the sites with no problems.  I can ping the sites from the Web Filter as well with no problems.  The problem lies within trying to ping/traceroute from our internal core router.  I get a "Destination unreachable" back from the router.  Nothing has changed in either router to make this happen.  I have checked, double checked and triple checked DNS and Name-Servers.  I have cleared the ARP Cache and the DNS Cache on our routers and DNS servers.  I have cleared Temp Internet files, Cookies and even gone as far and building a machine from scratch to test this theory.  Somewhere between the firewall and the outside internet router, something is lost in translation......here is an example of the network.....

INTERNET ROUTER (outside of firewall)  xxx.xxx.xxx.xxx
Sonicwall Pro Firewall               Wan port xxx.xxx.xxx.xxx    Lan port 192.168.1.3
Network Core Router (LAN Port of firewall)  192.168.1.1

This network has been in place and functioning for quite sometime and now these certain sites aren't accessible.  I have also run repeated tests for spyware/adware/malware/viruses and checked the hosts files for redirects.  Please let me know what information I can provide to someone to help me resolve this issue.  I have contacted the ISP as well and they report no trouble, which is proven through the traceroutes and pings from the internet router.  I can only assume that it's a routing issue with the core router or the firewall.

Thanks.....
0
Comment
Question by:Timothy Kashin
  • 2
3 Comments
 
LVL 4

Accepted Solution

by:
celsmk earned 2000 total points
ID: 12610432
Hi,

Looks like you have got MTU size problems. Some of your routers are not handling well path MTU and is dropping larger packets.

Please look at these threads:

A problem similar to yours:
http://www.experts-exchange.com/Networking/Q_20621043.html?query=Path+MTU%2C+web&clearTAFilter=true

A way to diagnose fragmentation sizes in your network path:
http://www.experts-exchange.com/Networking/Q_20025708.html?query=Path+MTU%2C+web&clearTAFilter=true


Hope this helps.

Regards,

Celsmk
0
 
LVL 3

Author Comment

by:Timothy Kashin
ID: 12644791
Actually, I found what the issue was.  It was a pain to nail down, but here goes....
n our network are the following components/appliances...
Core Router
Internet Router
Sonicwall Firewall Pro
St. Bernard Webfilter
Messagescreen Spam appliance.

The problem is the person prior to my employment here setup the network and had the core router (192.168.1.1) as the gateway.  Eash other appliance pointed this way as well.  This seemed to be working fine, but, in all reality the firewall (192.168.1.3) should have been the default route for internet traffic.  Once I found this discrepancy, everything starting working beautifully.

Thanks for the suggestions though.......

Tim
0
 
LVL 3

Author Comment

by:Timothy Kashin
ID: 12644804
Mods, please award Celsmk 100pts and an A for effort on this one.  I did make some MTU adjustments as well after I found the root cause and it made a difference as well.
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article is a guide to configure bridging on Cisco Routers.  This is something I never knew was possible until after making a few phone calls to Cisco.  Using bridging saved our company money by not requiring us to purchase a new switch.  Bridgi…
In the world of WAN, QoS is a pretty important topic for most, if not all, networks. Some WAN technologies have QoS mechanisms built in, but others, such as some L2 WAN's, don't have QoS control in the provider cloud.
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

850 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question