sh ip socket...

DLS2#sh ip sock
Proto    Remote      Port      Local       Port  In Out Stat TTY OutputIF
 17   --listen--                       10.1.200.253     1985   0   0 1001   0
 17   --listen--                       10.1.200.253     1975   0   0   11   0
 17 0.0.0.0             0            10.1.200.253     2228   0   0  211   0
 17 10.1.80.1          67         10.1.200.253       67   0   0 2211   0
 17   --listen--                        10.1.200.253      161   0   0 1001   0
 17   --listen--                        10.1.200.253      162   0   0 1011   0
 17   --listen--                        10.1.200.253    59533   0   0 1011   0
 17   --listen--                             --any--           161   0   0 20001   0
 17   --listen--                             --any--           162   0   0 20011   0
 17   --listen--                             --any--         54711   0   0 20001   0
 17   --listen--                         10.1.200.253      123   0   0    1   0
 17 10.1.50.1         514          10.1.100.253    57448   0   0 400201   0

note in the protocol field, 17, udp...

ports, well known...

67           dhcp
161-62    snmp
514         syslog
123         ntp

there was a reason they wanted you to memorize protocol and port numbers...

switchport identification...

use sh ver to find the mac address assigned to a switch...

sw2950_02#sh ver
Cisco Internetwork Operating System Software
IOS (tm) C2950 Software (C2950-I6K2L2Q4-M), Version 12.1(22)EA14, RELEASE SOFTWA

Processor board ID FHK0619X14J
Last reset from system-reset
Running Standard Image
24 FastEthernet/IEEE 802.3 interface(s)

32K bytes of flash-simulated non-volatile configuration memory.
Base ethernet MAC Address: 00:09:B7:3F:CE:80


so what is the mac of port 1?

sw2950_02#sh int fa0/1
FastEthernet0/1 is up, line protocol is up (connected)
  Hardware is Fast Ethernet, address is 0009.b73f.ce81 (bia 0009.b73f.ce81)

how about fa0/10? better know hex...

sw2950_02#sh int fa0/10
FastEthernet0/10 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce8a (bia 0009.b73f.ce8a)

15 is easy...

sw2950_02#sh int fa0/15
FastEthernet0/15 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce8f (bia 0009.b73f.ce8f)

16 is not...

sw2950_02#sh int fa0/16
FastEthernet0/16 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce90 (bia 0009.b73f.ce90)

the ten's position incremented by one remainder zero is fa0/16...


which makes fa0/24 easy... what is 16 plus 8...

sw2950_02#sh int fa0/24
FastEthernet0/24 is down, line protocol is down (notconnect)
  Hardware is Fast Ethernet, address is 0009.b73f.ce98 (bia 0009.b73f.ce98)

junk in the trunk...

sw2950_02(config)#int fa0/2
sw2950_02(config-if)#switchport nonegotiate
first, DTP (dynamic trunking protocol) is cisco proprietary and will not work with gray market switches...  use nonegotiate in a mixed environment... this disables DTP, will only become a trunk with ON or NONEGOTIATE ports, and  port ranges are not allowed with this command

sw2950_02(config)#int fa0/2
sw2950_02(config-if)#sw mode trunk
trunking is on... DTP signals are sent to the other connected port to initiate trunking if it is ON, AUTO, or DESIRABLE

if:
sw2950_02(config-if)#sw mode dynamic desirable
the port will become a trunk after detecting DTP signals of  ON, AUTO or DESIRABLE from the connected port

if:
sw2950_02(config-if)#sw mod dyn auto
the port will become a trunk if the other port is ON or DESIRABLE

if:
sw2950_02(config-if)#no sw mod trunk
trunking and DTP are disabled and this is the desired state for access ports; no dynamic establishments can occur

today's post was brought to you by Michael the network cat...

Guster the love muffin...

 and Craze, the queen of the domain...