Module 1 Lesson 3: STP

Used to prevent layer 2 bridging loops
PVST+ default
- One STP instance per VLAN
- Cisco proprietary

Phase I - Root Bridge Election
- "root" of the spanning-tree
- Election based on BID
- Bridge Priority
- MAC Address

Phase II - Root Port Election
- Upstream port closest to root bridge.


STP ROOT PORT ELECTION
- Upstream port closest to root bridge
- Root port election based on
- Lowest cumulative cost
- Inverse value based on interface bandwidth
- Lowest upstream BID
- Used to isolate multiple connections to upstream same bridge
- Lowest port ID
- Lowest port priority
- Lowest port number

Portfast
- Forward through listening and learning phases
BPDU Filter
- If BPDU is received revert out of portast state
BPDU Guard
- If BPDU is received shut port down
Root Guard
- If superior BPDU is received shut port down
Uplinkfast
- Immediately transition alternate ports to forwarding when root port is lost
BackboneFast
- Expire max age when inferior BPDU is received on root port
Loop Guard
- Prevent unidirectional links

Comments

Post a Comment

Popular posts from this blog

BGP Communities

Community Attribute The community attribute provides a way of grouping destinations, called communities, to which routing decisions (such as acceptance, preference, and redistribution) can be applied. Use route-maps to set them. no-export - Do not advertise this route to EBGP peers. no-advertise - Do not advertise this route to any peer. internet - Advertise this route to the Internet community; all routers in the network belong to it.
Read more

Hector Runs Over a Cat

Image
Hector informed me today that he ran over a cat. I asked him if he stopped and he said "I slowed down". I asked him if he was going to bury it but he would not. I then gave him a ride home and pulled up next to the 3 day dead mangled cat and Hector wouldnt look at it. I took a picture and MMS him so he could see what he had done to this poor defenseless animal. I offered to help him bury it but he just seems so callus. I am posting this picture to try to get Hector to help me bury this cat. Please post your thoughts and suggestion for Hector. I think he just needs a hug.
Read more