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CCIE Ethernet
Study questions for CCIE Written
48
Computer Networking
Professional
01/03/2012

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Cards

Term
What pins does a PC NIC card transmit on?
Definition
Pins 1 and 2
Term
What pins does a PC NIC card receive on?
Definition
Pins 3 and 6
Term
What pins does a switch transmit on?
Definition
Pins 3 and 6. "3, 6 -- switch transmits"
Term
What pins does a switch receive on?
Definition
Pins 1 and 2.
Term
How can the switch detect link speed?
Definition
1) Via Fast Link Pulses (FLP) in the auto-negotiation process
2) Based on incoming electrical signal
Term
What is the default duplex for a 1 G port?
Definition
Full duplex
Term
What is the default duplex for a 10 or 100 Mbps port?
Definition
half-duplex
Term
How many bytes in an 802.3 MAC header?
Definition
22
8 -- preamble and start of frame
6 -- dest MAC
6 -- source MAC
2 -- Type/Length
Term
What is the FCS in 802.3?
Definition
4 byte frame check sequence at the end of the frame.
Term
What 3 functions does 802.3 perform?
Definition
Medium access, error detection and framing.
Term
What IEEE standard defines Ethernet Link Layer Control (LLC)?
Definition
802.2
Term
What function does 802.2 LLC provide?
Definition
Allows multiple upper layer protocols to share use of data link.
Term
What are the fields in 802.2 header?
Definition
1 byte -- DSAP (destination service access point)
1 byte -- SSAP (source SAP)
1 - 2 bytes -- Control (allows for connection or connectionless operation, generally only for connectionless with a 1 byte value of 0x03)
Term
What does a DSAP value of 0xaa indicate?
Definition
0xaa is an indication to use SNAP and look at 5 additional bytes in header for upper layer protocol.
Term
What are the fields in the SNAP header?
Definition
3 bytes -- OUI (but rarely used)
2 bytes -- type (upper layer protocol)
Term
What is the IEEE standard for Fast Ethernet over copper and optical?
Definition
802.3u
Term
What is the IEEE standard for GigE over optical?
Definition
802.3Z
"you can Z far with optical"
(100 km with 1000Base-ZX)
Term
What is the IEEE standard for GigE over copper?
Definition
IEEE 802.3ab
Term
Of what significance is the leftmost bit in canonical bit order?
Definition
Leftmost is least significant.
Term
What are the two most significant bits in the 1st byte of a MAC address?
Definition
U/L | I/G

Most significant: I/G
Second most significant: U/L
Term
What is the I/G bit for in a MAC address?
Definition
0 if this is a unicast address
1 if this is a multicast/broadcast address
Term
What does it mean if the U/L bit is set to 0 in a MAC address?
Definition
U/L bit = 0 means this is a vendor assigned MAC address.
Term
What does it mean if the U/L bit is set to 1 in a MAC address?
Definition
U/L = 1 means this is an administratively assigned MAC address
Term
What is the only defined MAC Control frame in the MAC Control Sublayer?
Definition
The MAC Control PAUSE frame is sent to multicast address 0180.C200.0001 to tell the receiver to wait before sending more frames.
Term
When is the use of Ethernet flow control negotiated?
Definition
The use of PAUSE frames for flow control happens during auto negotiation.
Term
What is used for auto-negotiation on GigE links?
Definition
Next-Page-Exchange
Term
When is auto-negotiation appropriate?
Definition
Use auto-negotiation when connecting to end users or transient users.
Term
When is it best to hard-code speed and duplex?
Definition
Switch to switch, switch to server, switch to router.
Term
Can you auto-negotiate speed and hard-code duplex?
Definition
No, speed must be manually configured before duplex is manually configured.
Term
What color is a err-disabled port LED?
Definition
orange
Term
What are 5 causes of errDisable?
Definition
1) Excessive collisions (> 16 in a row)
2) bpduguard
3) UDLD
4) Etherchannel misconfig
5) L2 protocol tunnel config
Term
Name 3 causes of flooding in switched networks and possible solutions.
Definition
1) Asymmetric routing (fix: configure switch MAC aging time = router ARP aging time 14400 seconds)
2) Frequent TCNs (minimize with use of portfast)
3) forwarding table overflow (use 802.1X or psec)
Term
How many destination span ports can be configured per switch?
Definition
64
Term
If you are monitoring a tx session on a port, which of the following are applied before going to SPAN port: ACL, VACL, QoS, policing?
Definition
All of them. For tx SPAN sessions, ACL, VACLs, QoS and policing are applied before traffic is spanned.
Term
How do you send SPAN traffic from one device to another without routing?
Definition
Use RSPAN to configure a special "remote span" VLAN on all switches between source and destination.
Term
What technology enables routing of spanned traffic?
Definition
ERSPAN uses GRE tunnels to route spanned traffic.
Term
What is VLAN 199 given this config:
vlan 199
remote span
Definition
Vlan 199 is an RSPAN vlan.
Term
What ACL numbers can be used for MAC address ACLs?
Definition
700 - 799, 1100-1199
Term
What ACL numbers can be used for ethernet type ACLS?
Definition
200-299
Term
What is the MTU of a PPPoE frame?
Definition
1492 bytes (accounts for 8 byte header that PPP adds)
Term
What happens to a PPPoE connection if MTU doesn't match between client and server?
Definition
The PPPoE negotiation will fail.
Term
What protocol enables the concept connection or circuit on Ethernet and adds features to protect against IP and MAC conflicts and rogue DHCP servers?
Definition
PPPoE users can virtually "dial" from one machine to another over an Ethernet network, establish a point to point connection between them and then securely transport data packets over the connection
Term
How do you disable auto-negotiation on an Ethernet port?
Definition
Manually configure speed AND duplex.
Term
What's the quickest way to enable vtp pruning in a domain?
Definition
Configure it on the server.
Term
What are two motivations for PVLANs?
Definition
1) Better LAN security
2) IP subnet conservation (separate VLANs on same subnet)
Term
What kind of PVLAN can talk to primary VLAN and others in their secondary VLAN (but not any other secondary VLAN) ?
Definition
Community (e.g. Employee ports)
Term
What kind of PVLAN can talk to primary VLAN but no others in any secondary VLAN (including their own)?
Definition
Isolated (e.g. Guest ports)
Term
In RSTP, which timers (Hello, fwd delay, etc) does a switch use -- its own or the roots?
Definition
Always the root. One of the roles of the root bridge is to set timers and properties of the tree
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