HOW TO ROUTING

Unanswered Question
Apr 24th, 2007

hi, i just new in cisco i have cisco 1841, i already configure both Fastethernet and & serial0/0 and subinterface0.1. My problem is i can't ping the serial 0 ip using my PC. (ie. RtrLAN-ip 10.10.10.1, serial0.1 - 192.168.98.2, ISP-ip 192.168.98.1). Using my router i can ping the ISPip but in PC i cant ping. Please help. thanks

I have this problem too.
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Anand Narayana Tue, 04/24/2007 - 03:05

hi Jamer,

make sure that u had given ur router's Fastethernet IP address(10.10.10.1) as a gateway IP on ur PC (the PC should also be on the same network).

hope this helps.

rate this post if satisfied.

ltjamer19 Tue, 04/24/2007 - 03:11

hi,

yup my gateway for my pc is 10.10.10.1 but still i cant ping the 192.168.98.1. but i can ping the 192.168.98.2.

Richard Burts Tue, 04/24/2007 - 03:13

The suggestion about default-gateway on the PC is an excellent place to start and is frequently the cause of this kind of problem. Another part that frequently causes this kind of problem is not doing proper translation of addresses. You may have a route to get to the ISP (and to the Internet) but they probably do not have a route to get to your LAN (since it is using network 10 addresses. So you need Network Address Translation to translate your inside addresses to something that the ISP can recognize and route to.

[edit] If you can ping your end of the serial but not the other end of the serial it makes it even more likely that the problem is that the ISP does not have a route back to you. NAT is the solution.

HTH

Rick

ltjamer19 Tue, 04/24/2007 - 03:23

Hi rburts,

I already contacted the ISP and they already configure my LAN 10.10.10.1 as static. Using my router i can ping the ISP IP side. NAT is good but i have some application that need port forwarding. My router doesn't support port application mapping.

Thanks,

Eric

desai.jaideep Tue, 04/24/2007 - 03:10

Hi

Can you pls post the router configuration if you have configured the PC correctly......

Regards

JD

Anand Narayana Tue, 04/24/2007 - 03:15

Hi Jamer,

just you need to put an ip route entry.

ip route 0.0.0.0 0.0.0.0 192.168.98.2

if still you can ping, then you need do NAT on your router, which will translate ur private ip address in to public ip address what ever is mentioned on the NAT pool.

hope this helps.

rate this post if satisfied.

Richard Burts Tue, 04/24/2007 - 03:18

His end of the serial connection is 192.168.98.2 so the static route should be ip route 0.0.0.0 0.0.0.0 192.168.98.1.

But if he can ping his end but not the provider end, then I do not believe that the problem is a missing route on his end. I believe that it is on the ISP end.

HTH

Rick

ankbhasi Tue, 04/24/2007 - 03:22

Hi Friend,

I also believe that your ISP does not have a route back to your lan ip and it will never have also so you have to NAT your lan ip with your serial interface ip when it leaves the router.

Also I believe for reaching the ISP IP I do not need any static or default route on router but yes to reach somewhere other than my own connected subnet I do need a default route which I believe is not correct as per the config "ip route 192.168.98.0 255.255.255.0 192.168.99.1" where I am not sure how come 192.168.99.1 is coming into picture.

Regards,

Ankur

ltjamer19 Tue, 04/24/2007 - 03:30

Hi Ankur,

My ISP declear my LAN 10.10.10.1, in fact he can ping my router LAN.

Thanks,

Eric

ankbhasi Tue, 04/24/2007 - 03:37

Hi Eric,

Can he also ping any ip address on your lan or just your lan interface?

Can you try extended ping from your router to ping your isp with source ip address of your lan interface?

Regards,

Ankur

ltjamer19 Tue, 04/24/2007 - 03:52

Hi Ankur,

No he cannot ping other ip in my network, he can only ping my lan interface. Using my router i can ping ISP IP.

Thanks,

Eric

ankbhasi Tue, 04/24/2007 - 04:36

Hi Eric,

This means that your ISP had configured only a host route and not a network route and that is the reason he is able to ping only the lan interface and not anything other than that in same subnet.

So now you have 2 ways to achieve the desired results, either ask your ISP to have a route for lan subnet rathar than host ropute for lan interface or configure NAT on your router.

HTH

Ankur

*Pls rate all helpfull post

Richard Burts Tue, 04/24/2007 - 03:21

Thanks for posting the config. It confirms my suggestion that there was no address translation. Either the ISP must have a route to your network 10 addresses or you must translate your addresses into addresses that the ISP will recognize and can route to.

Also I note a typo mistake in the config. Your default route is:

ip route 192.168.98.0 255.255.255.0 192.168.99.1

and it should be:

ip route 192.168.98.0 255.255.255.0 192.168.98.1

HTH

Rick

ltjamer19 Tue, 04/24/2007 - 03:25

Hi Rick,

Sorry for the typographical error 192.168.99.1 is already corrected. but still same problem

Thnks,

Eric

ankbhasi Tue, 04/24/2007 - 03:27

Hi Eric,

Configure NAT on your router or else it will not work. ISP cannot have static routes for all your LAN subnets. You can have multiple subnets configured on your LAN and ISP will never have a static route back to your each and every subnet so once you NAT you lan ip with your serial ip ISP will see the packets coming from your serial interface and will reply back to your router.

Regards,

Ankur

mohammedmahmoud Tue, 04/24/2007 - 03:58

Hi Eric,

All you need is a default route on your router "ip route 0.0.0.0 0.0.0.0 192.168.98.1", and set the default gateway for your PCs to 10.10.10.1 (and don't forgot to close the firewall on your machine while testing), and ask your provider to add static route for your LAN IPs.

HTH,

Mohammed Mahmoud.

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