Daily Archives: February 28, 2013

2.1.c Implement and troubleshoot VLAN

2.1.c [iii] Normal, extended VLAN, voice VLAN


In order to facilitate a loop free topology a root switch is elected as a reference point for the entire tree. This is accomplished by establishing a BID (bridge id) for every switch in the diameter. A bridge ID is an 8 byte construct composed of 2 bytes of priority, and 6 bytes MAC address. Further, the priority is segmented into 4 bits priority and 12 bits extended system id, where the extended system id is the VLAN ID.



Spanning tree enabled protocol rstp

Root ID Priority 32778

Address 0009.b73f.ce80

Cost 12

Port 64 (Port-channel2)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec


Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)


32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 8 4 2 1


here is the binary math with the example vlan 10


1000 0000 0000 1010


32768 + 8 + 2

3.6.a Describe packet types

3.6.a [i] LSA types [1, 2, 3, 4, 5, 7, 9]

this is a great article…

OSPF route calculation overview

1) Routers establish adjacencies to flood topological information. The flooding process in OSPF is pretty complicated, and ensures the LSAs are delivered to all routers in a single area. As mentioned, topological information is carried in the form of LSAs and cannot be filtered, which it is essential to the OSPF algorithm. The only thing that limits LSA propagation is the flooding domain associated with the particular LSA type. Using the topological information learned, all routers within an area build the consistent graph of the network connections.

the rest is here: