CCNP switch slides 12 Flashcards
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http://www.coursehero.com/flashcards/430760/CCNP-SWITCH-642-813-InterVLAN-routing/
What are the two types of port queues on a switchport?
ingrees queues, and egress queues.
What three decisions must be made after the switch processes the ingress queue?
Where to forward the frame, where it should be forwarded, and how. All happen simultaneously.
What is the FIB in multilayer switching?
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.
What table contains the Layer 2 information for every next-hop entry in the FIB?
The adjacency table.
What two components are part of the TCAM operation?
Feature Manager and Switching Database Manager.
What is another name for Topology-based Multilayer switching?
Cisco Express Forwarding (CEF).
By default how long are CAM table entries kept before they are deleted?
300 seconds.
What are the name differences between the Layer-3 and Layer-2 forwarding tables?
-Layer-2 is the CAM.-Layer-3 is the FIB.
What is the max cable length of most X-BASE-T wiring?
100m (328 ft)
ACLs on a switch can identify frames based on what 5 features?
MAC address, non-IP protocol types, IP Addresses, Protocols, and Layer-4 port numbers.
What is ARP throttling, or throttling adjacency mean?
That until an APR reply is received, additional ARP requests will dropped so they don’t fill up the input queues.
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?
The MAC address, the switch port, and the VLAN on which it arrived.
TCAM entries are organized by which of its three components?
Mask.
What three things are contained in the Hex-value when looking at the FIB adjacency table?
-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).
If an error is detected on a switchport what happens to it?
It is placed in the errdisable state, and disabled.
Will a FIB contain host routes (/32) entries?
Yes. Even though most routing tables do not (unless manually configured) the FIB does.
What are the four types of adjacency’s that can be found in the FIB adjacency table?
Null, Drop (actual error), Discard (ACL or policy), and Punt.
What are the two techniques of CEF that use specialized hardware?
-aCEF, functions as a FIB cache.-dCEF, has its own FIB table and forwarding engine!
Within a frame, what does an Ethernet switch use to make decisions about forward frames?
The destination MAC address.
What is the command to view the FIB?
(exec)show ip cef
What is a ‘CEF Glean’?
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.
What is an LOU and when is it used?
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.
What command establishes a DHCP relay to another network?
(if)ip helper-address IP
In multilayer switching, what 4 specific decision are made simultaneously to forward data?
-The L2 forwarding table(CAM)-The L3 forwarding table(FIB)-Security ACLs.-QoS ACLs.
What are the two types of multilayer switching (MLS)?
-Route caching, basically route-once-switch-many.-Topology based, uses the layer-3 routing table (called FIB) to make a forwarding decision.
What is the DHCP DORA process?
Discover (any servers), Offer (address info), Request (to use the offer), ACK (that its ok to use the offer).
What is unknown unicast flooding?
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.
What is the IEEE standard for 10 GigE?
802.3ae
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?
The L2 source and destination MAC, the L3 TTL and L3 header checksum, and the L2 checksum.
If set to automatic recovery, an errdisabled port will stay down for how long? What is the range for configuring this time?
300 seconds, and 30-86,400 seconds.
In topology-based multilayer switching, is the shortest or longest match used as the layer-3 destination?
The LONGEST match is always considered the best match.
In a switch, what is the CAM?
Content-Addressable Memory, or the address table. It holds the MAC, egress port, VLAN ID, and a time stamp.
What are TCAM entries composed of?
-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.
What is the IEEE standard for Gigabit Ethernet? (over copper)
802.3ab
What 5 basic commands are needed to configure DHCP on a multilayer switch?
ip dhcp exclude-address START ENDip dhcp pool NAMEnetwork IP MASKdefault-router IP1 IP2 IP3 etc…lease [infinite, D H M)
What is the IEEE standard for FastEthernet?
802.3u
When a packet is ‘punted’ what does this mean?
That the packet was unable to be forwarded naturally and is sent to the switch CPU for process switching.
Each TCAM mask can have/has how many values associated with it?
8 Values for each Mask
Is duplex autonegotiation possible on Gigabit Ethernet?
No, because Gigabit Ethernet is, by definition, Full Duplex.
What are the 9 reasons that a packet can be ‘punted’?
-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.
What does the Switching Database Manager do in TCAM?
It configures and manages TCAM partitions.
What is the IEEE standard for Gigabit Ethernet? (over fiber)
802.3z
What are the two Physical classifications of 10 GigE?
-LAN PHY, Connects switches, usually in the Core layer.-WAN PHY, Connects to SONET or SDH networks, typically in MANs.
What does the Feature Manager do in the TCAM?
It merges any ACLs into the TCAM table so that it can be processed at hardware speeds.
