Term
| Within a frame, what does an Ethernet switch use to make decisions about forward frames? |
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Definition
| The destination MAC address. |
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Term
| If a switch receives a frame and the source MAC is not in it's forwarding table, what information will be stored about the new frame? |
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Definition
| The MAC address, the switch port, and the VLAN on which it arrived. |
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Term
| What is unknown unicast flooding? |
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Definition
| When a switch receives a frame and the destination MAC is not in its forwarding table, it forwards the message (or floods) out all ports on the same VLAN as the source. |
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Term
| What are the two types of port queues on a switchport? |
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Definition
| ingrees queues, and egress queues. |
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Term
| What three decisions must be made after the switch processes the ingress queue? |
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Definition
| Where to forward the frame, where it should be forwarded, and how. All happen simultaneously. |
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Term
| In a switch, what is the CAM? |
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Definition
| Content-Addressable Memory, or the address table. It holds the MAC, egress port, VLAN ID, and a time stamp. |
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Term
| ACLs on a switch can identify frames based on what 5 features? |
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Definition
| MAC address, non-IP protocol types, IP Addresses, Protocols, and Layer-4 port numbers. |
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Term
| What are the two types of multilayer switching (MLS)? |
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Definition
-Route caching, basically route-once-switch-many.
-Topology based, uses the layer-3 routing table (called FIB) to make a forwarding decision. |
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Term
| In topology-based multilayer switching, is the shortest or longest match used as the layer-3 destination? |
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Definition
| The LONGEST match is always considered the best match. |
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Term
| What is another name for Topology-based Multilayer switching? |
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Definition
| Cisco Express Forwarding (CEF). |
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Term
| What is the FIB in multilayer switching? |
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Definition
| The FIB is the Forwarding Information Base, and is a table of layer-3 routing information used to hardware switch packets. It contains the next hop address for each entry. |
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Term
| What are the name differences between the Layer-3 and Layer-2 forwarding tables? |
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Definition
-Layer-2 is the CAM.
-Layer-3 is the FIB. |
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Term
| In multilayer switching, what 4 specific decision are made simultaneously to forward data? |
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Definition
-The L2 forwarding table(CAM)
-The L3 forwarding table(FIB)
-Security ACLs.
-QoS ACLs. |
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Term
| When multilayer switching, what information must be changed in the packet and frame, by the packet rewrite engine, before the data can be forwarded out a port? |
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Definition
| The L2 source and destination MAC, the L3 TTL and L3 header checksum, and the L2 checksum. |
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Term
| When a packet is 'punted' what does this mean? |
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Definition
| That the packet was unable to be forwarded naturally and is sent to the switch CPU for process switching. |
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Term
| What are the 9 reasons that a packet can be 'punted'? |
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Definition
-ARP requests and replies
-IP packets needing a response (TTL, MTU, frag
-IP broadcasts
-Routing protocol updates
-CDP packets
-IPX routing packets
-Packets needing encryption
-Packets triggering NAT
-Non-IP and non-IPX packets. |
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Term
| By default how long are CAM table entries kept before they are deleted? |
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Definition
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Term
| What two components are part of the TCAM operation? |
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Definition
| Feature Manager and Switching Database Manager. |
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Term
| What does the Feature Manager do in the TCAM? |
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Definition
| It merges any ACLs into the TCAM table so that it can be processed at hardware speeds. |
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Term
| What does the Switching Database Manager do in TCAM? |
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Definition
| It configures and manages TCAM partitions. |
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Term
| What are TCAM entries composed of? |
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Definition
-Values, Mask, and Result (VMR) combinations.
-Values are 134-bit, containing source and dest IP address and protocol information.
-Masks are 134-bit (self explanatory)
-Results are numeric values that represent what action to take. |
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Term
| TCAM entries are organized by which of its three components? |
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Definition
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Term
| Each TCAM mask can have/has how many values associated with it? |
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Definition
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Term
| What is an LOU and when is it used? |
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Definition
| Logical Operation Unit, used when an ACL line uses a port operator like gt, lt, or range. The Feature Manager uses this to compile the TCAM entry for the ACL. |
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Term
| What is the max cable length of most X-BASE-T wiring? |
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Definition
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Term
| What is the IEEE standard for FastEthernet? |
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Definition
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Term
| What is the IEEE standard for Gigabit Ethernet? (over fiber) |
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Definition
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Term
| What is the IEEE standard for Gigabit Ethernet? (over copper) |
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Definition
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Term
| Is duplex autonegotiation possible on Gigabit Ethernet? |
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Definition
| No, because Gigabit Ethernet is, by definition, Full Duplex. |
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Term
| What is the IEEE standard for 10 GigE? |
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Definition
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Term
| What are the two Physical classifications of 10 GigE? |
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Definition
-LAN PHY, Connects switches, usually in the Core layer.
-WAN PHY, Connects to SONET or SDH networks, typically in MANs. |
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Term
| If an error is detected on a switchport what happens to it? |
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Definition
| It is placed in the errdisable state, and disabled. |
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Term
| If set to automatic recovery, an errdisabled port will stay down for how long? What is the range for configuring this time? |
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Definition
| 300 seconds, and 30-86,400 seconds. |
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Term
| Will a FIB contain host routes (/32) entries? |
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Definition
| Yes. Even though most routing tables do not (unless manually configured) the FIB does. |
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Term
| What are the two techniques of CEF that use specialized hardware? |
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Definition
-aCEF, functions as a FIB cache.
-dCEF, has its own FIB table and forwarding engine! |
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Term
| What table contains the Layer 2 information for every next-hop entry in the FIB? |
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Definition
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Term
| What three things are contained in the Hex-value when looking at the FIB adjacency table? |
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Definition
-The first 6 octets are the Hex value of the next hop MAC address.
-the second 6 octets are the Source MAC for the layer 3 engine interface (like VLAN 99).
-the last two octets are the EtherType (0800 for Ethernet). |
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Term
| What are the four types of adjacency's that can be found in the FIB adjacency table? |
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Definition
| Null, Drop (actual error), Discard (ACL or policy), and Punt. |
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Term
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Definition
| When a L3 forwarding engine cannot forward a packet because of missing L2 info, the time it takes to have the L3 engine generate an ARP request and figure out the L2 information is the CEF Glean. |
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Term
| What is ARP throttling, or throttling adjacency mean? |
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Definition
| That until an APR reply is received, additional ARP requests will dropped so they don't fill up the input queues. |
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Term
| What is the command to view the FIB? |
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Definition
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Term
| What is the DHCP DORA process? |
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Definition
| Discover (any servers), Offer (address info), Request (to use the offer), ACK (that its ok to use the offer). |
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Term
| What 5 basic commands are needed to configure DHCP on a multilayer switch? |
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Definition
ip dhcp exclude-address START END
ip dhcp pool NAME
network IP MASK
default-router IP1 IP2 IP3 etc...
lease [infinite, D H M) |
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Term
| What command establishes a DHCP relay to another network? |
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Definition
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