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Highlighted
Advisor

Re: Routing through switch

Hi,

I don't know how I didn't noticed this before but  if you have a linksys router to go on the internet then it is probably doing the NAT so you don't need to

and you must give your default route this router as next hop.

To make a simple sketch just draw with paint and do a screenshot  and post the switch  config, on switch issue sh cd nei detail and same on 1841.

Regards.

Alain.

Don't forget to rate helpful posts.
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Beginner

Re: Routing through switch

Thanks for the info Alain.

I was trying to replace the linksys witht he 1841.  When I had the linksys router connected and performed a trace route I was able to hit everyhop that was listed before the internet.

The school has blocked pings past a certain point.

The last hop is a 172.16.31 network.

The default gateway that is listed for a seperate port in the same room is 192.168.247.254

I can ping both of these but no internet access.

Is there anyreason why different ports in the same room would have different gateways?

Thanks for the help

Highlighted
Beginner

Re: Routing through switch

Hello,

How are you testing for Internet access, with a web broswer?  I noticed that your DHCP pools you created on the router don't provide DNS servers as part of the address assignment.  If you are not manually setting the DNS servrers on the PC to get around this, it will not know how to look up the websites that you try to access.

You can try adding this command to your DHCP pools:

     dns-server 4.2.2.1 4.2.2.2

Where 4.2.2.1 and 4.2.2.2 are publicly accessible DNS servers.  If your school doesn't allow outbound DNS traffic, you'll have to find out what the internal DNS servers that you need to use are and swap them in place of 4.2.2.1 and 4.2.2.2.

Hope that helps.

Andy

Highlighted
Beginner

Re: Routing through switch

Hi Andy,

It appears that when the router obtains the dhcp address for Fa0/0 it is automatically getting the dns servers.

When I type ping yahoo.com, I am seeing the correct ip translation.  If this is just an illusion please let me know.

Thanks

Chris

Highlighted
Beginner

Re: Routing through switch

It is possible that the DNS servers from the Fa0/0 interface are getting passed along.  I've never actually dealt with a secnario where the router is obtaining it's address from DHCP, it's always been set statically.  But, if you are swapping back and forth between the working Linksys and the Cisco router, it also could be that you have yahoo.com and any other names that you looked up while on the linksys stored in your DNS cache.  The ping command would use the cached address if it is available.  One quick way to find out is do "nslookup yahoo.com" from a command prompt and see if you actually get a response back from the DNS server(s).  You could also do "ipconfig /flushdns" (assuming you are using Windows) to clear the cache and then try the ping again to see if it still works.

Andy

Highlighted
Beginner

Re: Routing through switch

Sorry for the confusion.  I have attached an image of the setup.

This is what I am trying to achieve.

If you replace the 1841 with the linksys I can connect to the internet.

If the 1841 is connected to the wall, I have the cisco router obtaining ip from dhcp when plugged into the wall.

Highlighted
Advisor

Re: Routing through switch

Hi,

What devices does this sketch represent? Is the router your 1841? what is this L2 switch below? Is the router directly connected to this

L3 switch on the right and where is the internet connection?

Can you do a sh cdp nei on the router please and a sh ip arp.

Regards.

Alain.

Don't forget to rate helpful posts.
Highlighted
Beginner

Re: Routing through switch

The diagram is how I was picturing it.  Am I understanding correctly that your trace route makes it to the same

point before stopping with both the 1841 and the Linksys?

Also, for the router passing along the DNS settings thatit receives on Fa0/0 to it's DHCP clients, this is possible.  However it also looks like you need a command for it to do this that is not appearing in your config examples above.  You would need to enter:

ip dhcp pool mypool

     import all

The other settings you specify in the pool config, such as lease and default router, will override what is imported from the dhcp client on Fa0/0.

Did you try the nslookup or ping after clearing the DNS cache?  It still seems to me like it may just be a name resoltion issue, especailly if your trace routes do look the same when done on the 1841 and the Linksys.

Highlighted
Beginner

Re: Routing through switch

Here is the trace route performed when connected to the 1841:

tracert yahoo.com

1  1ms     1ms        1ms      10.10.10.1

2     1 ms     1 ms     1 ms  192.168.179.254
  3    23 ms     1 ms     1 ms  172.31.67.161
  4     3 ms     5 ms     2 ms  172.31.6.149
  5     *        *        *     Request timed out.

The 179.254 is the multiswitch on the otherside of the wall.

The router to the left of the wall is the 1841, and the L@ switch is the cisco 2960 catalyst switch.

I am having no issues with the 2950.  I have no access to the L3 switch.

I will have access to the router on thursday.

Highlighted
Beginner

Re: Routing through switch

Hi Guys,

I pulled this info by plugging directly into the port:

GW: 192.168.179.254

DHCP Server: 192.168.179.253

I have also retrieved the 2 DNS Servers.

Would setting the DNS info router fix this?

Also would it be possible to set the dhcp server to 192.168.179.253 or would my ap address dhcp be taking care of this?

Thanks for the input