any way to view host IP from router?

superbabe_uk

I was wondering if there is any to have a router display the IP addresses of its connected hosts?

- something similar to cdp neighbors

thanks!

ehnde

superbabe_uk wrote: »

I was wondering if there is any to have a router display the IP addresses of its connected hosts?

- something similar to cdp neighbors

thanks!

You typically wouldn't have hosts directly connected to a router, unless it's a multi-layer device of some sort with more than a few ports. You can try using

show ip route
or
show ip int brief

...or if you haven't assigned addresses

show log

could be useful.

Your running config is likely to have the information you are wanting as well. Now if your hosts are connected to a switch, try this from your switch:

show mac?

Take a look at the mac address table to see your hosts on the switch.

Hope that helps!

miller811

ping the broadcast address
ie 192.168.1.255

the run show arp

phobophile

I figure show arp would achieve what you are looking for.

Example (some details omitted, production network!):

ROUTER#sh arp
Protocol  Address          Age (min)  Hardware Addr   Type   Interface
Internet  10.xxx.xxx.1             -   xxxx.xxxx.xxx1  ARPA   FastEthernet0/1.xxx
Internet  10.xxx.xxx.2             0   xxxx.xxxx.xxx2  ARPA   FastEthernet0/1.xxx
Internet  10.xxx.xxx.5             6   xxxx.xxxx.xxx3  ARPA   FastEthernet0/1.xxx
Internet  10.xxx.xxx.6             0   xxxx.xxxx.xxx4  ARPA   FastEthernet0/1.xxx
Internet  10.xxx.xxx.7             0   xxxx.xxxx.xxx5  ARPA   FastEthernet0/1.xxx

From there, if you have the hosts on a switch, then switch to the router, you can ran a show mac-address-table command on the switch.

SWITCH#sh mac-address-table 
          Mac Address Table
-------------------------------------------

Vlan    Mac Address       Type        Ports
----    -----------       --------    -----
 xxx    xxxx.xxxx.xxx1    STATIC      Fa0/19 
 xxx    xxxx.xxxx.xxx2    STATIC      Fa0/10 
 xxx    xxxx.xxxx.xxx3    STATIC      Fa0/6 
 xxx    xxxx.xxxx.xxx4    STATIC      Fa0/12

And then, if you know what device is plugged into what switch port, you can use an output modifier (|, aka "pipe") when issuing the sh arp command again on the router, to locate that single IP address.

ROUTER#sh arp | inc xxxx.xxxx.xxx4
Internet  10.xxx.xxx.6             2   xxxx.xxxx.xxx4  ARPA   FastEthernet0/1.xxx

I assume that is the information your looking for, but if someone else has another suggestion, please let us know.

superbabe_uk

beautiful. thanks guys!

chrisone

If your router is providing DHCP services you can see how many IP addresses you have leased and to whom. That is another method of finding out who is connected.