WITH NAT FTP is Working but HTTP is NOT...

[haarisalibaig]

Hi,

I have 1760 Router with one WIC-1T & one WIC-1ADSL. My Internet is connected to the ADSL Port. I have configured NAT & I can Access FTP but cant access HTTP (Internet Browsing). From the client side i was able to ping yahoo but could not able to browse the website even i telneted to some of my live sites on INTERNET. I connected a DSL modem & tested everything was working (INTERNET BROWSING). what could be the issue with router configurations???? Please check the attachment for Router configuration..

Thanks...

[globalnettech]

Hello,

this sounds like a problem with name resolution. Try and take those lines out of your configuration:

ip name-server 210.x.11.11

ip name-server 203.x.52.1

ip name-server 213.x.14.6

ip name-server 213.x.14.8

In general, with ADSL, the provider takes care of the name resolution, without you having to specify the IP addresses yourself.

Can you give that a try and check if it makes a difference ?

Regards,

GNT

[haarisalibaig]

hi,

i tried putting manual DNS of the ISP on the client machine...i was able to ping yahoo (by name) i was geting a reply the same time i was not able to browse the sites...

Regards,

[Edison Ortiz]

You may be facing IP Fragmentation. I didn't see any commands on how to avoid it in your router and the dialer interface is fragmenting the ethernet packet from 1500 to 1492.

Please read this article on ways to overcome this issue

http://www.cisco.com/en/US/tech/tk827/tk369/technologies_white_paper09186a00800d6979.shtml

Please rate helpful posts.

Thanks

[sundar.palaniappan · Accepted solution]

Hi,

This is a common problem associated with DSL connections. The devices on the service provider network mayn't support a MTU of 1500-bytes and hence, some packets may get dropped.

Configure 'ip tcp adjust-mss 1400' on fastethernet0/0 interface. The router would lower the agreed MSS value to 1400-bytes between the tcp client and the server and may very well resolve your problem.

Hope that helps!

Regards,

Sundar

[Richard Burts]

While my instinct agrees with Sundar that it may be an MTU issue over the DSL and that ip tcp adjust-mss may fix the problem I note that in the original post Mirza states that he can access FTP but not HTTP. FTP is at least as likely as HTTP to use maximum size packets when it is transfering a file. Perhaps Mirza can clarify whether his access to FTP was transfering a file of some size or was just to login through FTP.

HTH

Rick

[jackyoung]

There is another way to test the MTU is to use the ping with large packet, e.g. "ping www.yahoo.com -l 1500" at your windows client.

You can adjust the 1500 to lower value to verify that packet size is working. However, if the 1500 is workable then there may be another issue.

Hope this helps.