router and ip of switch

[Mary]

in the router, I try show cdp neighbour, but nothing comes out, how to know the ip of the switch, which is connected to the router

[nseit_aanjum1]

Router#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface s1
Router(config-if)#no cdp enable

USE THIS COMMAND TO THE PORT THROUGH EHICH THE SWITCH IS CONNECTED.HOPE U WILL ABLE TO SEE SH CDP NEIGHBOR.

[Mary]

no cisco switch, it is the other band switch, so is it possible to see the IP from cisco router, I also has a checkpoint firewall connected, so is it able to see the firewall IP from cisco router, thanks

[Richard Burts]

We still do not know enough about this environment to be able to answer your question. You have told us that it is not a cisco switch but have told us very little else about the switch. Probably most important is whether the connection between the switch and the router is an access port or a trunk port? And also is it a managed switch or an unmanaged switch? Is there a single vlan on the switch or multiple vlans?

As I said in a previous post you could look in the ARP table of the router for the IPs that are connected on the interface which connects to the switch. If the router knows the IP of the switch then it would be in the ARP table. If the switch IP is not in the ARP table then I do not believe that you will find it on the router.

HTH

Rick

[pwwiddicombe]

cdp enable on the interface connected to the switch.

Note the switch also needs to have cdp enabled on the connecting port.  Note this will ONLY show the directly attached neighbor; and wouldn't pass through an intermediate provider network in most cases.

[Richard Burts]

Show cdp interface might be one way to determine whether CDP is enabled on the interface or not. And in looking at this problem we need to also consider the possibility that CDP was turned off globally and not just on this interface. And there is always the possibility that CDP is not running on the switch interface.

An alternative approach which does not depend on CDP would be to do show arp on the router and to look at the entries associated with the interface where the switch is connected. It might be a bit tedious depending on how many devices are connected through that interface. But if the switch has a working IP address it should be included in the arp output.

HTH

Rick

[Joseph W. Doherty]

Just to add something to Rick's note, the two devices are Cisco devices (with a direct connection)?

[Richard Burts]

Joseph raises a couple of good points, that we need to understand what kind of switch, what kind of router, and how they are connected. Is this switch a layer 2 switch or a layer 3 switch?  In addition it would be very helpful to know a bit more about the switch and its connection to the router. Are there multiple vlans on the switch? Is the connection from the switch to the router a trunk or an access port?

HTH

Rick