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weird problem with using a Cisco 1751 as a home office router

Hi, all. I was wondering if you could help me with a glitch I keep hitting.

I just bought a new Cisco 1751 router, and completed configuring it to access the Internet and provide internal LAN addresses. For some reason I have the ability to access certain websites (such as

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but cannot perform certain functions such as connecting to MSN messenger (the application just times out)

I'm not quite sure what I'm doing wrong with the configuration at this point

If anyone has any ideas, I would really appreciate it. I am supplying a copy of the running config as well as the output from Show version

cisco1751#sh ver Cisco Internetwork Operating System Software IOS (tm) C1700 Software (C1700-K9O3SY7-M), Version 12.3(20), RELEASE SOFTWARE (f c2) Technical Support:

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(c) 1986-2006 by cisco Systems, Inc. Compiled Tue 08-Aug-06 17:59 by kesnyder Image text-base: 0x8000816C, data-base: 0x810A3620

ROM: System Bootstrap, Version 12.2(1r)XE1, RELEASE SOFTWARE (fc1) ROM: C1700 Software (C1700-K9O3SY7-M), Version 12.3(20), RELEASE SOFTWARE (fc2)

cisco1751 uptime is 4 minutes System returned to ROM by power-on System restarted at 05:12:12 UTC Tue Jun 27 2006 System image file is "flash:c1700-k9o3sy7-mz.123-20.bin"

This product contains cryptographic features and is subject to United States and local country laws governing import, export, transfer and use. Delivery of Cisco cryptographic products does not imply third-party authority to import, export, distribute or use encryption. Importers, exporters, distributors and users are responsible for compliance with U.S. and local country laws. By using this product you agree to comply with applicable laws and regulations. If you are unable to comply with U.S. and local laws, return this product immediately.

A summary of U.S. laws governing Cisco cryptographic products may be found at:

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If you require further assistance please contact us by sending email to snipped-for-privacy@cisco.com.

cisco 1751 (MPC860P) processor (revision 0x600) with 81920K/16384K bytes of memo ry. Processor board ID JAD06380IIJ (43364424), with hardware revision 0000 MPC860P processor: part number 5, mask 2 Bridging software. X.25 software, Version 3.0.0.

1 Ethernet/IEEE 802.3 interface(s) 1 FastEthernet/IEEE 802.3 interface(s) 32K bytes of non-volatile configuration memory. 16384K bytes of processor board System flash (Read/Write)

Configuration register is 0x2101

cisco1751#sh run Building configuration...

Current configuration : 1818 bytes ! ! No configuration change since last restart ! version 12.3 service timestamps debug datetime msec service timestamps log datetime msec service password-encryption ! hostname cisco1751 ! boot-start-marker boot-end-marker ! enable secret xxxx ! memory-size iomem 25 mmi polling-interval 60 no mmi auto-configure no mmi pvc mmi snmp-timeout 180 no aaa new-model ip subnet-zero ! ! ip dhcp excluded-address 192.168.1.254 ! ip dhcp pool MYPOOL import all network 192.168.1.0 255.255.255.0 default-router 192.168.1.254 dns-server 206.47.244.138 67.69.184.223 ! ip cef ip audit po max-events 100 vpdn enable ! vpdn-group 1 request-dialin protocol pppoe ! ! ! username kenjg password 7 001D02031350590008 ! ! ! ! ! interface Ethernet0/0 no ip address half-duplex pppoe enable pppoe-client dial-pool-number 1 hold-queue 100 out ! interface FastEthernet0/0 ip address 192.168.1.254 255.255.255.0 ip mtu 1492 ip nat inside speed auto ! interface Dialer1 description DSL mtu 1452 ip address negotiated ip nat outside encapsulation ppp dialer pool 1 dialer-group 1 ppp authentication chap callin ppp chap hostname xxxx ppp chap password xxxx ppp pap sent-username xxxx password xxxx ! ip nat inside source list 101 interface Dialer1 overload ip classless ip route 0.0.0.0 0.0.0.0 Dialer1 no ip http server no ip http secure-server ! ! access-list 1 permit 192.168.1.0 0.0.0.255 access-list 1 permit 192.168.2.0 0.0.0.255 access-list 101 deny tcp any any eq telnet access-list 101 permit ip 192.168.1.0 0.0.0.255 any access-list 101 permit ip 192.168.2.0 0.0.0.255 any ! ! line con 0 password xxxx login line aux 0 line vty 0 4 password xxxx login ! end

Reply to
ken gallagher
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I'm going to put on my special Cisco Certified Psychic Network hat...

"Oh great spirits, show me an image of what ails this man's network!"

"It's appearing... it's appearing... Yes Yes, I am getting a clear picture of a DSL connection!"

Say, whaddya know? That funny little man in the store that wasn't there the next day didn't cheat me on that CCPN hat after all!!

So what you have is an MTU problem. Make sure your systems are configured to use Path MTU Discovery; if that doesn't work, try lowering their MTU.

You might be able to use a noticably larger MTU on the DSL, but that depends on the provider. We used to have to use 1452 around here, but they modernized a few years ago and 1492 works here now. That would -help- with the MTU problem, but it would not fix it.

I'm not overly familiar with the 175x IOS capabilities. Check to see if you can do TCP MSS Adjustment in your IOS version.

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Reply to
Walter Roberson

Maybe try;

interface Ethernet0 ip tcp adjust-mss 1452

interface Dialer1 ip mtu 1492

Reply to
user

Thanks all for the advice. The problem is fixed I had the wrong MTU settings as you all thought

Reply to
ken gallagher

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