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Routing/vlan issues

Hi Guys,

Ive got a question for you!

I have been asked to reconfigure some cisco switches for a company.

What they are essentially doing is changing their IP address range from a prublic range to a private range.

They have 5 x 3560 catalyst switches. They use the default Vlan but want me to configure each switch to use a different subnet (10.6.0.254 for one, 10.5.0254 for another switch etc).

They have a DHCP server connected to one of the switches (the main switch) which will give the clients of each switch an IP address in their subnet range depending on what switch they are connected to.

I have changed the Vlan ip address for 3 of the switches and updated the ip helper command to the appropriate IPs, 2 of the switches, the main switch and one located in an opposing building can see each other fine and the clients connect to the network fine and recieve IP address from the DHCP server, but the 3rd switch (which the remaining 2 switches connect to) does not communicate properly.

when i try to ping it from the main switch i get no reply. but if i am on the problem switch i can ping the other switches no problem. This means that the clients connected to the problem switch are unable to recieve DHCP information.

I have input static routes to each IP range of the switches but still no joy.

Am i missing something obvious like a service that i have not enabled/configured? The switches were working fine before hand with the public ip address.

Is there anything you would recommend me checking?

Thanks in advance,

6 REPLIES
VIP Super Bronze

Re: Routing/vlan issues

Hi Warren,

Since the 3rd switch can ping other switches with no problems and since you are using static routes then that means you have configured switch 3 static routes correct.  Now you need to check switch 1 and 2 and make sure that they are pointing to the right IP address of switch 3.

HTH

Reza

Cisco Employee

Re: Routing/vlan issues

Hi,

Do you mean you can ping from the 3rd switch to the main switch and not from the main switch to the 3rd switch ?

Routing issue are usually resolved by checking the routing table hop by hop (same thing as trace route)

Laurent.

New Member

Re: Routing/vlan issues

Thanks for the replies,

I can ping the main switch from the 3rd switch, but not the other way round. On the 3rd switch i can connect to the other switches to modify their settings but when trying to connect to the 3rd switch from the main the requests timeout just like the pings.

Its baffling me!

the switches are connected to each other via fibre connections and the switch to switch links use a 192.168 ip subnet. i have discovered that on the main switch i can ping 192.168.3.1 which is the interface on switch 5 (its connected to switch 3). so this means i can ping other switches connected to this switch but not switch 3 itself?

out of interest, on switch 2 i am unable to ping the dhcp server which is connected to the main switch. but the clients all work ok. dont know if this helps.

Thanks,

VIP Super Bronze

Re: Routing/vlan issues

Can you post a diagram of your network and show the subnets and point out the problem switch?

New Member

Re: Routing/vlan issues

As requested.

The problem switch is TC-96, on this switch i can ping 10.4.0.254 and 10.5.0.254 no problem, but from the MB switch i cannot ping 10.6.0.254 or its int of 192.168.1.2.

The red indicates the changes i have made.

From MB i can also ping 192.168.3.2 which is the fibre (gigab) interface on MD.

scan0001.jpg

Cisco Employee

Re: Routing/vlan issues

The link is broken and I can't see your diagram. Can you attached it as a file instead ?

Also did you check the routing table of all your switches to verify the expected next-hop and output interface is used to join the destination address ?

Is IP routing well activated everywhere ? Be sure to use extended ping where you specify both the source and destination IP addresses.

Thanks

Laurent.

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