Mapping out a network
I may move part of this into a separate guide section if I create more guide like posts. This is a very rough draft, so it is not very cohesive. Version 2 I would organize it more along with creating an actual visual map to show each section then a final map with everything connected.
I am aware that some other vendors have automatic visual map. I just have not worked with them outside of a Unifi switch that I have at home currently. They also don’t seem to be fully reliably. For example:
In this automatically generated chart it shows the Unifi Wireless AP’s Port 1 connects back to the Unifi Switch on Port 16. However if you look at Laptop C930 it also shows it is on port 16. Which it does lead back to that port, but it actually connects through Port 2 on the Unifi AP in the other room. In the new Unifi network topology it also looks like the Flex Mini switch is online when it hasn’t been powered on for over a year.
In the older Unifi interface it correctly doesn’t show at all in the topology view. Though with testing it also doesn’t show the laptop plugged into the Wireless AP Port 2 just shows port 16.
Note: most of these commands are for Cisco , however the general idea still applies with other vendor equipment. For example :(Cisco show mac address table, Allied Telesis/Dell : show bridge address table)
Example Devices:
Router: fc:d4:f2:aa:bb:c1
Root Switch: 24:16:9d:aa:bb:23
Switch 1: 24:16:9d:aa:bb:11
Switch 2: 24:16:9d:aa:bb:47
Switch 3: 24:16:9d:aa:bb:33
Switch 4: 24:16:9d:aa:bb:59First find the root switch that is connected to the Router. In this case I’ll use a Linux computer as the example as I usually work on Linux routers at work. ip addr list eth0 You should see similar to this:
Grab the MAC Address (Example MAC: fc:d4:f2:aa:bb:c1)
Then go to the switch that you think is the core. If you have no idea, then just check every switch you discover until you find it.
show mac address-table address fc:d4:f2:aa:bb:c1
Verify the port is correct
show mac address-table interface
Note down all your switches that you think have. Switch 1, Switch 2, Switch 3, ect.
Now to do some shortcuts if possible: If LLDP is enabled you can find other devices that also use LLDP. It will sometimes even show the hostname/mac of the device
Show lldp neighborsSwitch4# show lldp neighbors
Port Device ID Port ID System Name
------- ----------------- ----------------- -------------------
1/e6 24:16:9d:aa:bb:23 gi1/1/26 Root Switch
1/e9 64:16:00:00:00:01 gi1 Polycom Note: This won’t work on older Cisco devices as they didn’t support LLDP. If CDP is enabled you can also note those quick too. (Mostly Cisco Only Devices)
Show cdp neighborsSW3#show cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone
Device ID Local Intrfce Holdtme Capability Platform Port ID
50000000000006 Fas 0/24 162 S I SG300-10P gi10
SEP4CBC48000001 Fas 0/24 142 H P IP Phone Port 1
Switch-11 Fas 0/24 150 S I WS-C3550- Fas 0/24
Switch-22 Fas 0/24 151 S I WS-C3550- Fas 0/24
Root_Switch Fas 0/24 168 S I SG350X-48P gi10Show spanning tree is how you can find the other switches that are running spanning tree (STP). Which most switches should all be using STP on the ports. To make sure spanning tree is enabled on all ports run:
show spanning-treeYou should see similar to this on the core of the network:
Root_Switch# show spanning-tree
Spanning tree enabled mode RSTP
Default port cost method: short
Root ID Priority 0
Address 24:16:9d:aa:bb:23
This switch is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Number of topology changes 64 last change occurred 651:28:23 ago
Times: hold 1, topology change 35, notification 2
hello 2, max age 20, forward delay 15
Interfaces
Name State Prio.Nbr Cost Sts Role PortFast Type
------ -------- -------- --------- ------ ---- -------- -----------------
1/e1 enabled 128.1 19 Frw Desg No P2P (RSTP)
1/e2 enabled 128.2 19 Frw Desg No P2P (RSTP)On the switches that aren’t root you’ll see what port is determined as the best path to the root switch.
show spanning tree detailLook for details such as:
Root port is 24 (FastEthernet0/24)"
Designated root........24:16:9d:aa:bb:23
Designated bridge......24:16:9d:aa:bb:33 <ROOT or OTHER MAC HERE>
Designated port id is 128.XXIf the designated bridge address doesn’t match the root mac, then there is another switch in-between it and the root. The Port ID is the port of the switch that it connects directly to. For example if you have switches connected like this:
Root_Switch port 1 > Switch_1 port 23 > SW7 port 48
Root will be Root Switch's Address 24:16:9d:aa:bb:23
SW7 Designated bridge will be SW1
SW7 Designated port id should show 128.23
If you also had
SW CORE A Port 3 > SW2 port 22 > SW6 port 47
Root will be Switch A
SW2 Designated bridge will be Root
SW2 Designated port will be 128.3
SW6 Designated bridge will be SW2
SW6 Designated port will be 128.22For example:
Switch7# show spanning-tree
Root ID Priority 0
Address 24:16:9d:aa:bb:23
Cost 19
Port 24 (FastEthernet0/24)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768)
Address 24:16:9d:aa:bb:11
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300You can see how 7’s next bridge is Switch 1’s address. Which is the path it will take to get to the root switch address.
Note: Ports that go beyond 48 may be higher speed ports(Such as Gigabit or 10 Gigabit) or ports of a stacked switch
1/g1 enabled 128.49
1/g2 enabled 128.50
1/g3 enabled 128.51
1/g4 enabled 128.52
2/e1 enabled 128.53
2/e2 enabled 128.54Further beyond those steps if STP is not enabled. Looking by mac address is the one of the last few options.
show mac address-table address <MAC HERE>Verify the port is correct
show mac address-table interface <PORT HERE>