Subject:
How to find out the port number by IP address
Solution:
In core
switch, ping the IP address,
Ex:
[email protected]#ping 10.20.12.111
Sending 1, 16-byte ICMP Echo to 10.20.12.111, timeout
5000 msec, TTL 64
Type Control-c to abort
Reply from 10.20.12.111 : bytes=16 time=1ms TTL=128
Success rate is 100 percent (1/1), round-trip
min/avg/max=1/1/1 ms.
[email protected]#
And then:
[email protected]#sh arp 10.20.12.111
IP Address Mac Address Type Age Port
Status
1 10.20.12.111 6c62.6d99.023c Dynamic 1 1/19 Valid
[email protected]#
And we find one device be connected to Port:1/19
But the device‘s IP address is 10.20.12.111?
Let show MAC address again.
[email protected]#sh mac ethernet 1/19
Total active entries from port 19 = 10
MAC-Address
Port Type Index VLAN
0012.f20c.d234
1/19 Dynamic 15838
2
001b.78a5.1abb
1/19 Dynamic 1186
11
6c62.6d99.023c 1/19
Dynamic 9116 12
0022.641b.a7d6
1/19 Dynamic 14968
11
0022.641b.a89f
1/19 Dynamic 7876
11
1cc1.de13.3269
1/19 Dynamic 14167
11
0015.5d0c.6f0b
1/19 Dynamic 10006
12
4061.86c6.9d40
1/19 Dynamic 567
11
9cb6.543a.d6b6
1/19 Dynamic 9426
11
000d.f411.af84
1/19 Dynamic 5002
12
[email protected]#
We can find not only 6c62.6d99.023cdevice communication by this switch port. So we know
a switch or router be connected to this switch port number.
Let me show fdp(Cisco named CDP) neighbor.
[email protected]#sh fdp neighbors ethernet 1/19
Device ID: HF-OA-B1-1C
configured as tag-type8100
Entry address(es):
IP address:
10.20.0.20
Platform: FES4802 Switch, Capabilities: Switch
Interface: ethernet1/19
Port ID (outgoing port): ethernet50 is TAGGED in
following VLAN(s):
2 11
Holdtime : 122 seconds
Foundry Networks, Inc. FES4802, IronWare Version
03.6.00cTc1 Compiled on Oct 31 2006 at 22:18:23 labeled as FES03600c
One device named HF-OA-B1-1C be connected to this
port.
Now let‘s login this switch by telnet.
Let‘s ping the IP address: 10.20.12.111 at first.
[email protected]#ping 10.20.12.111
Sending 1, 16-byte ICMP Echo to 10.20.12.111, timeout
5000 msec, TTL 64
Type Control-c to abort
Reply from 10.20.12.111 : bytes=16 time<1ms TTL=127
Success rate is 100 percent (1/1), round-trip
min/avg/max=0/0/0 ms.
[email protected]#^C
[email protected]#
And then let‘s show the mac address:
[email protected]#sh mac-address
Total active entries from all ports = 31
MAC-Address Port Type
VLAN
6c62.6d99.0129
50 Dynamic 12
6c62.6d99.0309
50 Dynamic 12
6c62.6d99.023f
50 Dynamic 12
6c62.6d99.023c 7
Dynamic 12
d067.e531.3ec0
50 Dynamic 12
02e0.52ea.ca0c
50 Dynamic 12
02e0.52c5.ca0b
50 Dynamic 11
02e0.522e.ca02
50 Dynamic 2
9cb6.543a.d6b6
22 Dynamic 11
000d.f411.d7d2
50 Dynamic 12
0012.f21a.da00
50 Dynamic 11
0012.f21a.da12
50 Dynamic 11
000d.f410.c492
50 Dynamic 12
0015.5d0c.6f0b
7 Dynamic 12
000d.f411.c18e
50 Dynamic 12
000d.f411.4920
50 Dynamic 11
0022.641b.a7d6
21 Dynamic 11
0022.641b.a89f
14 Dynamic 11
4061.86c8.12a1
50 Dynamic 11
0012.f21b.2500
50 Dynamic 11
000d.f411.af84
7 Dynamic 12
MAC-Address Port Type
VLAN
4061.86c6.9d60
50 Dynamic 12
4061.86c6.9d40
25 Dynamic 11
001b.78a5.1abb
23 Dynamic 11
001c.c41e.a6cf
50 Dynamic 11
1cc1.de13.3269
16 Dynamic 11
0012.f21a.da12
50 Dynamic 12
0012.f21b.2500
50 Dynamic 12
0012.f21a.da12
50 Dynamic 2
0012.f21b.2500
50 Dynamic 2
0012.f21a.da00
50 Dynamic 12
We can find the mac-address 6c62.6d99.023c matching with IP address, and the switch port
number is 7. but we find not only the mac address
communication by this switch port. Let‘s check it again. We find one a small
hub is connected to this switch port. So we can ignore this small HUB and think
the device directly connected to this port.
Now we have found the switch port.