Chapter 10 Flashcards
CDP
Cisco Discovery Protocol. Discovers basic info about neighboring routers, switches without needing to know passwords for those devices
CDP works by
Devices send out advertisements with information about them. Other devices listen and take note
IEEE version of CDP
LLDP, Link Layer Discovery Protocol
What can be used to confirm or fix the documentation in a network diagram?
CDP
Two ways CDP sends info, depending on the medium
On ethernet, CDP uses broadcasts. On other media, CDP sends frames to any known data link address
Details CDP includes
Device identifier (hostname, usually) Address list (network and data link address) Port ID (interface that sent the CDP advertisement) Capabilities list (information on the type of device: router, switch) Platform (model and OS version running on the device)
show cdp neighbors [type number]
Lists summary line of information about each neighbor, or just the neighbor found on a specific interface, if an interface was listed
show cdp neighbors detail
lists one large set of info for all neighbors
show cdp entry [name]
lists detailed information for a specific neighbor.
What interfaces should have CDP enabled
Any switch port connected to another switch, a router, or an IP phone
Interface subcomands to disable CDP
no cdp enable
interface subcommands to enable CDP
cdp enable
global command to disable CDP for all interfaces
no cdp run
When an interface with autonegotation connects to an interface without autonegotiation, how does the first device determine duplex configuration
Based on speed
When an interface with autonegotation connects to an interface without autonegotiation, how does the first device determine duplex configuration when speed is not known
10mbps, half duplex
When an interface with autonegotation connects to an interface without autonegotiation, how does the first device determine duplex configuration when speed is 10 or 100 mbps
half duplex
When an interface with autonegotation connects to an interface without autonegotiation, how does the first device determine duplex configuration when speed is 11,000Mbps
full duplex
What problem could cause both ends of an ethernet segment to report up/up (connected) even when the connection doesn’t work
duplex mis-match. switches still report that hte connection is up.
Runts
frames that did not meet the minimum frame size requirement (64 bytes, including destination/source MAC, type, and FCS). Can be caused by collissions
Giants
Frames that exceed the max frame size requirements (1518 bytes, including source/destination MAC, type FCS)
Input Errors
Total of many counters, including runts, giants, no buffer, CRC, frame, overrun, and ignored counrts
CRC errors
Received frames that did not pass the FCS math; can be caused by collisions
Frame errors
received frames that have an illegal format, for example, ending with a partial byte. Can be caused by collissions
Packets output
Total number of packets (frames) forwarded out the interface
