RSTP Alternative Port vs Backup Port

The following is some basic info on STP and RSTP. This list is not comprehensive. Refer to the link at the bottom of the page for more in depth details.

RSTP Priority

Default Priority is 32768 + VLAN ID

For example, if we are using vlan 10, then our default priority is 32768 + 10 = 32778

RSTP Priority can be set from 0 – 61440 in increments of 4096.

RSTP Port Roles

Ports can fill 1 of 4 roles.

Port RoleDescription
Root PortPort closest to the Root Bridge (Switches going to the Root switch)
Designated PortPorts going away from the Root Bridge (To clients)
Alternate PortA “backup” port for the Root port. If the Root Port fails, this port takes over
Backup PortEssentially a backup port for the designated port
RSTP Port Roles

RSTP Port States

A port can be in one of 3 states. Well technically 4 states if you include down/unplugged.

Port StateDescription
DiscardingPort discards packets (Alternate and Backup Ports)
LearningPort learns MACs and doesn’t forward data
ForwardingPort forwards data and learns MACs
RSTP Port States

RSTP Port Types

There are 3 port Types. Not to be confused with port States or Roles.

Port TypeDescription
Point to PointSwitch to Switch
Point to Point EdgeEdge of Network. Connected to a PC, Printer etc.
SharedHalf Duplex, Port connected to a Hub
STP/RSTP Port Types

RSTP Timers

There are three RSTP timers. STP has the same timers, but the MaxAge is 10 seconds, and the Forward Delay is used for both Learning and Listening states which takes a total of 30 seconds to complete.

Timer NameDefault ValueDescription
Hello Timer2 SecondsTime between Hellos created by Root
MaxAge6 Seconds (Hello Timer * 3)How long a Switch should wait before trying to readjust the network
Forward Delay15 SecondsDelay used for Learning/Listening in STP. Shouldn’t be necessary if legacy bridges are not used.

Port Cost

There are technically two types of cost. The newer cost values were introduced so we could use faster ethernet speeds.

By default Cisco switches use the old cost values, but they can be changed to use the new ones.

spanning-tree pathcost method long
Ethernet SpeedOld CostNew Cost
10 Mbps1002,000,000
100 Mbps19200,000
1 Gbps420,000
10 Gbps22000
100 GbpsN/A200
1 TbpsN/A20
STP/RSTP Path Cost

More information can be found at the following link.

How to Stop a Continuous Ping on Cambium Radio

The Cambium equipment comes with a nice little ping utility when you SSH to it. Very simple to use. Maybe we should say too simple.

usage: ping <host>
       ping -n <count> <host>
                count = 0 for continuous ping

So if I want to continuously ping a website, say, I can put in the following

ping -n 0

Hit return and we are off to the races. But wait. I can’t get it to stop. Ctrl + C, doesn’t do anything, Ctrl + D or Ctrl +Z don’t help either.

Okay well fine. We’ll launch another terminal and ssh into it again and see what we can do. Excellent, now we are in aaand… wait… why are the ping results showing up here too? Help!!!

Buried in the heart of the helpful help command are these lines.

       ping -- Send ICMP ECHO_REQUEST packets to network hosts
    pingend -- End ICMP ECHO_REQUEST packets to network hosts

You don’t say. Well lets try typing in pingend with all the commotion going on in the terminal.

SSH+> pingend
Ping statistics for
        Packets: Sent = 3, Received = 3, Lost = 0 (0% loss)

Well good to know. Saves having to reboot the device.

Baicells eNodeB – Random Stuff

Looks like Default SSH port is 27149

Runs Quagga

CELL> show version
Quagga 0.99.21 ().
Copyright 1996-2005 Kunihiro Ishiguro, et al.

show network config

CELL> enable
CELL# show network
% Command incomplete.
CELL# show network config


CELL# show user
User      Permission    State
admin     admin         unlocked
anonymous admin         unlocked

User commands

CELL# user
 USERNAME User name
 add Add user
 delete Delete user
 lock User lock
 role User role
 unlock User unlock
CELL# user

Mikrotik – bridge port received packet with own address as source address (), probably loop

Sometime the following warning can show up in the log.

10:48:45 interface,warning ether2: bridge port received packet with own address as source address (74:4d:28:69:89:9d), probably loop

Check and verify that your interface MAC addresses are unique. VLANs look to be the exception as they should share the MAC address of the interface the VLAN is on.

More information in this thread.

Set static ip address in Ubuntu 19.04

The network configuration settings for the server edition of Ubuntu are now stored in the following location. Create the file if it does not exist.

sudo vi /etc/netplan/01-network-manager-all.yaml

Add or edit the config file to the following. Change eno1 to your interface name and the address and gateway to the appropriate IP’s

For more information, see netplan(5).
   version: 2
   renderer: networkd
      dhcp4: no
      addresses: []
        addresses: [,]

Now apply the changes with the following command.

sudo netplan apply

Find IP address from command line on Linux

Using ip command

ip add

example output

bob@localhost:~$ ip add
1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eno1: mtu 1500 qdisc mq state UP group default qlen 1000
link/ether 38:ea:a7:13:a4:fe brd ff:ff:ff:ff:ff:ff
inet brd scope global dynamic noprefixroute eno1
valid_lft 513sec preferred_lft 513sec
inet6 13ac::98fe::ae78:d1ff/64 scope link noprefixroute
valid_lft forever preferred_lft forever


You may need to install net-tools to use


example output

bob@localhost:~$ ifconfig 
eno1: flags=4163 mtu 1500
inet netmask broadcast
inet6 13ac::98fe::ae78:d1ff prefixlen 64 scopeid 0x20
ether b8:ac:6f:91:01:e8 txqueuelen 1000 (Ethernet)
RX packets 184950632 bytes 9487577263452
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 128473456 bytes 234612443785
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Using the hostname command

hostname -I

Output is just the IP address. Example below