10-14-2008 09:15 PM - edited 03-03-2019 11:55 PM
This one has got me stumped, i hope someone out there can help.
We have an 1841 with 2 x Fast Ethernet interfaces running IOS 12.4. We currenlty connect to the internet via a wireless link through this router on one of its Fast Ethernet interfaces. Behind this router we have 2 x 1721 routers segmenting the network further. The ISP has recently provided us with a new wireless connection that requires us to use PPPoE. I have adjusted the 1841 config and tested it, DNS resolution still works OK, I can still send and receive e-mail between our MS Exchange server and my webmail account with the ISP, finally, I can get to some websites, in particular those hosted here in New Zealand. However many other websites are no longer accessible, especially international websites. Here is the section of the config setup for PPPoE:
interface Null0
no ip unreachables
!
interface FastEthernet0/0
description $ETH-SW-LAUNCH$$INTF-INFO-FE 0$$ETH-LAN$$FW_OUTSIDE$
no ip address
no ip redirects
no ip unreachables
ip virtual-reassembly
no ip route-cache cef
no ip route-cache
duplex auto
speed auto
pppoe enable
pppoe-client dial-pool-number 1
no cdp enable
no mop enabled
!
interface FastEthernet0/1
description $ETH-LAN$$FW_INSIDE$
ip address 192.168.7.1 255.255.255.0
ip access-group 106 in
no ip unreachables
ip nat inside
ip virtual-reassembly
no ip route-cache cef
no ip route-cache
duplex auto
speed auto
no cdp enable
no mop enabled
!
interface Dialer1
ip address negotiated
ip access-group 103 in
ip mtu 1492
ip nat outside
ip virtual-reassembly
encapsulation ppp
dialer pool 1
no cdp enable
ppp authentication chap callin
ppp chap hostname REMOVED
ppp chap password 7 REMOVED
There are no problems routing to the internet with the previous wireless link. The problems occur after I make the changes. Please help as I really need to get this sorted out?
10-14-2008 09:40 PM
have you a default route 0.0.0.0 0.0.0.0 that goes via the outside interface?
can you add a diagram to understand more?
10-15-2008 02:12 AM
The default route i am using is:
ip route 0.0.0.0 0.0.0.0 Dialer1
My test computer is on the 192.168.7.x network, the same network as the LAN interface of this router, i am bypassing the proxy server and going stright through the router (configured as the PCs default gateway).
Some websites are accessible, particularly local New Zealand ones. Others, particularly international sites are not.
10-15-2008 08:04 AM
Hello Trevor,
the problem you describe points to a problem of routing of your public address.
If you have had MTU problems that were the first I thought of, you should be able to access some sites , some other slowly, some other could stuck but with no geographic correlation.
Try to use a looking glass that you can find here for different countries:
to check if your public address is known outside New Zeland.
Your provider could have just got the address block or other issue.
OR reduce the ip mtu also on the internal LAN side just to verify it is not an MTU issue.
This is something more likely then what I suggested above.
Hope to help
Giuseppe
10-15-2008 11:47 PM
Great thanks for that. I will try in the morning.
Another thing i found is:
ip tcp adjust-mss 1452
Should i use this on the fast Ethernet LAN interface?
10-16-2008 12:53 PM
Hello Trevor,
I would simply reduce the ip mtu on the LAN interface to make a test to understand if there is any MTU issue with new setup
use
int f0/0
ip mtu 1450
(just for a test)
Hope to help
Giuseppe
10-16-2008 01:45 PM
Hi Giuseppe,
I had already tried ip tcp adjust-mss 1452 on int fa0/0 before i received your last message.
Early indications are good in that internet access appears to be reliable now that i have made this change.
Do you think i should change the MTU size also?
Cheers,
Trev
10-16-2008 02:17 PM
Hello Trevor,
it was a suggestion for a test but your tests with ip tcp adjust-mss 1452 have proven effective.
You have fixed it and so I wouldn't make other changes for the moment.
I just don't understand why the issue was more present on international web sites.
Hope to help
Giuseppe
10-17-2008 01:29 PM
Sure, thanks.
I too am confused why it affected international sites mostly.
Anyway, all is good so far. Thank you for your help.
Cheers,
Trev
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: