Network PC World

The format of the original 802.1d bridge ID was redefined from two byte priority + MAC address to System ID extension mainly due to the advent of multiple spanning trees as supported by Per VLAN Spanning Tree Plus (PVST+) and IEEE 802.1s Multiple Spanning Trees (MST). With the old-style bridge ID format, a switch’s bridge ID for each STP instance (possibly one per VLAN) was identical if the switch used a single MAC address when building the bridge ID. Having multiple STP instances with the same bridge ID was confusing, so vendors such as Cisco Systems used a different Ethernet BIA for each VLAN when creating the old-style bridge IDs. This provided a different bridge ID per VLAN, but it consumed a large number of reserved BIAs in each switch.  The System ID Extension allows a network to use multiple instances of STP, even one per VLAN,  but without the need to consume a separate BIA on each switch for each STP instance. The System ID E...

In case you are finding it hard to reach default gateway from your newly installed Nexus 1000v virtual machine, here is one quick thing to check and configure before you can reach to the default gateway and other allowed subnets from your Nexus 1000v VM. Configure the management IP Address and default gateway on Nexus 1000v as per below commands conf t interface mgmt 0 ip address 192.168.0.100/24 exit vrf context management ip route 0.0.0.0/0 192.168.0.1 exit copy run start Note: Change the IP address as per your subnet.

Spanning-tree operation requires that each switch have a unique BID (Bridge ID). In the original 802.1D standard, the BID was composed of the bridge priority and the MAC address of the switch, and all VLANs were represented by a CST, Common Spanning Tree. Because Cisco started to use unique instance in PVST+ PVRST+ for each VLAN STP Process, there came need to provide Unique BID for each separate instance of STP per VLAN. So what Cisco Did! divided the Bridge priority field of 16 bits into two parts, 4 bits for priority and 12 bits for VLAN ID and named it as Extended VLAN ID. Now because only left most four bits are reserved for Bridge priority, you can only make the combinations of discrete values in increments of 4096 with those bits.

After I reset my Cisco Router 1841, It started to give error messages like below;  %Error opening tftp://255.255.255.255/network-confg (Timed out) %Error opening tftp://255.255.255.255/cisconet.cfg (Timed out) %Error opening tftp://255.255.255.255/router-config(Timed out) %Error opening tftp://255.255.255.255/ciscotr.cfg (Timed out) Actually these error messages are caused due to default configurations in Cisco IOS Software, which attempts to access the service configuration files from a network Trivial File Transfer Protocol (TFTP) server, and if the router is unable to acces the TFTP Server then it start displaying these messages. Yo can stop displaying these error message by entering following commands at Cisco CLI  Router#config terminal  Enter configuration commands, one per line.  Router(config)#no service  (this is command to stop these error messages) config Router(config)#end Router#write

You need to format the partition on which you want to install Linux Ubuntu and the type of Linux Format is completely different than those of Windows Format types. That's why hard disk partition on which Ubuntu is installed is not view able from Windows Operating System, because windows does not support Linux Ubuntu Formats.  This goes good until you want to both operating systems with dual boot system. When you do not want to use Linux Ubuntu you will have to convert its partition to NTFS or FAT32 in order to access the partition and store and access data from this partition. One method to convert Ubuntu partition to Windows is to convert and format the partition with Free MINITOOL Partition Program. Remember this procedure will only convert to Windows Supported partitions and will ask you to format the partition until you can use it. So you will loose any data on your Ubuntu partition.  See  How to access U...

This error is returned by Cisco IOS, when the trunking encapsulation is not set on one side of the switch and the other hand switch is configured properly. One of the case may be, when trunking between the port of a switch on one side and port of Switch-type interface on the router on other side. As you know that Dynamic Trunking Protocol, DTP, is not run by the Router so the Trunking can not be negotiated at this situation. To mitigate the error at this situation do the following steps; networkpcworld(config-if)#switchport mode trunk   Command rejected: An interface whose trunk encapsulation is "Auto" can not be configured to "trunk" mode.   Go to the desired Interface where you are getting this error networkpcworld (config)#int fa0/0/1 Enable trunk ecnapsulation manually  networkpcworld (config-if)#switchport trunk encapsulation dot1q Note:-  After setting encapsulation, most probably the switch interface would be converted to trunk by switchport mo...

Asynchronous transmission uses start and stop bits to signify the beginning bit ASCII character would actually be transmitted using 10 bits e.g.: A "0100 0001" would become "1 0100 0001 0". The extra one (or zero depending on parity bit) at the start and end of the transmission tells the receiver first that a character is coming and secondly that the character has ended. This method of transmission is used when data is sent intermittently as opposed to in a solid stream. In the previous example the start and stop bits are in bold. The start and stop bits must be of opposite polarity. This allows the receiver to recognize when the second packet of information is being sent. Synchronous transmission uses no start and stop bits but instead synchronizes transmission speeds at both the receiving and sending end of the transmission using clock signal(s) built into each component. A continual stream of data is then sent between the two nodes. Due to there being no st...