CCNP - Packet Forwarding Flashcards
What does CSMA/CD stand for?
Carrier Sense Multiple Access/Collision Detection
What is CSMA/CD used for? CSMA/CD is used in what type of network?
Ensure that only one device talks at a time in a collision domain Wired Networks
What is a collision domain? What is a network device where collisions can occur?
shared media that connects different network devices same media network where packet collisions can occur. ex. hubs, switches
What is the broadcast address used with MAC addressing?
FF:FF:FF:FF:FF:FF
What is a broadcast domain?
where a broadcast message can reach all devices on a subnet
What network devices are used to separate boundaries of broadcast domains?
routers
Is each port on a hub in the same or different collision domain?
same domain
Rather then flooding all the traffic out every port, what do switches maintain in order to forward traffic to the destination MAC address Where is that routing data stored?
MAC Address Table CAM or TCAM Table
What occurs when there is an unknown unicast?
is flooded to every switch port
What is a VLAN? Do VLANs create single or multiple broadcast domains on the same network switch?
Virtual Local Area Network multiple broadcast domains
What term are VLANs also know as?
SVI (Switch Virtual Interface)
By default do network devices in a VLAN communicate with other devices in a different VLANs
no
Can access ports be assigned to multiple or a single VLAN?
single VLAN
When packets are transmitted or received on an access port are 802.1Q tags included?
not included
What does the MAC Address table contain?
forwarding information of mac addresses mapped to assigned ports.
In the OSI model, which layer does all traffic start?
Layer 7 the application layer.
The ARP protocol is responsible for?
mapping mac addresses to switch ports
What three ways can packets be configured to route?
static route entry default-gateway routing protocol
What is a static route?
manually configured route to a destination network
What is a default-gateway?
default static route for all network traffic
What is a routing protocol used for?
route and distribute data and network information
What is a Routing Information Base-RIB?
Default routing table
What would be considered a routed interface?
any interface on a router
What does packet switching relate to?
Way packets are moved to/from the input interface to the output interface or interfaces to CEF
Process switching requires what to be personally involved with every forwarding decision? What layer does process switching take place?
CPU - every packet is inspected by the CPU (Software) L3
How does fast-switching work?
Packet passes and forward from the CPU once then stored in fast-switching route cache for faster access
How does Cisco Express Forwarding CEF work? Benefit of using Cisco Express Forwarding CEF
CEF caches routing information in the FIB (Forwarding Information Base) and Layer 2 next hop address in an adjacent table. (all in L2 data plane) Ability to forward more packets faster
How does CEF handle routing information in specialized ASICs?
Layer 3 routing table (RIB) is copied down into the (hardware level) L2 data plane and stored in both FIB (Forwarding Information Base) and (next hop) adjacent tables
What does ASIC stand for? What are ASIC used for?
Application Specific Integrated Circuit Integrated circuit (IC) for a particular use, rather for general-purpose use
What does TCAM stand for? What is the TCAM used for? Is TCAM an extension of the CAM architecture? True/False
Ternary Content Addressable Memory allowing the matching and evaluation of packets on more than one field. True
How are the TCAM entries stored?
Value, Mask and Result (VMR format)
What does the value in a TCAM indicate? What are those values?
value that should be searched IP address and protocol fields
What does the mask in a TCAM indicate?
field of interest that should be queried
What does the results in TCAM indicate?
action that should be taken with a match on the value and mask
What does CAM stand for? What is CAM used for?
Content Addressable Memory Store mac address and port information in a MAC address table
What do multi-layer switches use to forward frames and packets at wire speed?
ASIC hardware
What is centralized forwarding architecture?
When RP engine “route processor” is equipped to make all packet switching decisions/CPU.
What is distributed forwarding architecture?
When a packet is received on the ingress line card and then forwarded to the local forwarding engine.
What does the CEF - Software Forwarding Information base consist of?
Forwarding information base and Adjacent Table
What is the main advantage of distributed forwarding architecture Hardware CEF?
offloading packet switching responsibilities to line cards dCEF improves packet throughput performance.
What is the process of dCEF?
CEF data structures are downloaded to the forwarding ASIC and the CPUs of all the line cards to allow for switching to be done at the distribution level “data plane”
What is a RP route processor responsible for?
learning the network topology and building the route table “RIB”
Can a “RP” Routing Processor failure trigger routing protocol adjacency to reset resulting in packet loss and instability? True/False
True
What does the redundancy feature in stateful switchover (SSO) allows Cisco routers with two RPs to do?
synchronize router configuration and control plane state information
The process of mirroring information between “RPs” Route Processors is referred to as what?
checkpointing
During stateful switchover what two things happen immediately?
“RP” Route Processor immediately takes control and prevents problems such as interface link flaps.
What does CSMA/CA stand for? What is CSMA/CA used for? CSMA/CA is used in what type of network?
Carrier Sense Multiple Access / Collision Avoidance Reduces the possibility of a collision Wireless Networks
Is each port on a bridge, switch, router in the same or different collision domain?
separate domain
How many results does CAM tables provide?
only two results: 0 (true) or 1 (false)
How many results does TCAM tables provide?
three results 0, 1, and “X-don’t care.”
What does the forwarding engine perform?
Packet lookup and determines if that outbound interface is local, it forwards packet out a local interface. If the outbound interface is located on a different line card, packet is sent across the switch fabric, back plane, directly to the egress line card bypassing the RP.
