Cisco sg300 - port to IP mapping ?

Alexandre Takacs
Alexandre Takacs used Ask the Experts™
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Hello

is there a way to find out a mapping between physical port on the switch and the IP address of the connected device ?

Thanks & regards
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Sandeep GuptaConsultant

Commented:
more specifically..I think you want to see an IP address of the device connected to your cisco box?

if yes...

see your arp table..it will show you IP coming through connected port.

if it is DSL modem connected and you want to see the IP...then do "who" or "sh user"
Alexandre TakacsCTO

Author

Commented:
see your arp table..it will show you IP coming through connected port.
Hmmm... Here is what I get:

  VLAN 1   00:08:5d:82:d1:e4    GE6    
  VLAN 1   00:08:9b:cc:cb:85    GE48    
  VLAN 1   00:0f:fe:2d:00:4c    GE7    
  VLAN 1   00:12:79:48:a2:56    GE50    
  VLAN 1   00:14:c2:3b:11:08    GE49    
  VLAN 1   00:15:99:4b:ac:15    GE50    
  VLAN 1   00:16:46:a2:f6:ce    GE8    
  VLAN 1   00:19:66:2d:15:02    GE29    
  VLAN 1   00:21:9b:72:f6:d0    GE5    
  VLAN 1   00:21:9b:73:00:63    GE23    
  VLAN 1   00:22:19:ca:7e:16    GE24    
  VLAN 1   00:23:18:f3:4e:93    GE35    
  VLAN 1   00:23:f8:62:ea:81    GE52    
  VLAN 1   00:25:64:b2:17:37    GE14    
  VLAN 1   00:40:8c:78:a8:6f    GE26    
  VLAN 1   00:c0:b7:61:58:21    GE36    
  VLAN 1   08:00:37:8e:ae:a8    GE50    
  VLAN 1   08:2e:5f:bc:95:b3    GE12    
  VLAN 1   14:fe:b5:de:4b:6e    GE30    
  VLAN 1   3c:07:54:27:ff:55    GE35    
  VLAN 1   80:ee:73:40:71:0a    GE31    
  VLAN 1   8c:89:a5:7d:c4:26    GE15    
  VLAN 1   8c:89:a5:7d:c6:41    GE25    
  VLAN 1   8c:89:a5:7d:cb:f1    GE3    
  VLAN 1   bc:30:5b:b0:e3:4b    GE9    
  VLAN 1   bc:30:5b:b0:e3:7b    GE11

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Better than nothing but if i could resolve the MAC to IP it would be most useful...
Sandeep GuptaConsultant

Commented:
to which port of your device it is connected?

check cdp neighbor.
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Top Expert 2014
Commented:
That shows you the MAC address in the forwarding table and which port it see's that MAC address on.

That looks more like the output of "show mac table".  Not sure if on the SG300 the command to see the arp table is "show arp" or "show ip arp".  Try one of those, once you find the IP address you want to know about then do "show mac table | i x.x.x.x" where "x.x.x.x" is the IP address you want to know about.
TimotiStDatacenter Technician
Top Expert 2012

Commented:
You could enable DHCP snooping on the switch. That won't show you static IPs, though.

Tamas
Alexandre TakacsCTO

Author

Commented:
Sorry a bit late responding - no sure how to "enable DHCP snooping" ? Most of our IPs are dynamic so it would be a godd starting point.
TimotiStDatacenter Technician
Top Expert 2012
Commented:
Attached a CLI reference, see at "DHCP snooping".
Basically it inspects every DHCP request, and stores the IP addresses in them in a nice table on the switch. It's for preventing rogue DHCP servers primarily, but also great for port-to-IP mapping.

Tamas
CLI-300-1-2-5.pdf
Alexandre TakacsCTO

Author

Commented:
Thanks - I believe that with the various pointers you gave me I shall be able to figure out which IP is used on which port.

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