CCNP switch slides 4 Flashcards
source
http://quizlet.com/3373163/ccnp-switch-deck-4-flash-cards/
what do multilayer switches do?
both layer 2 switching and IVR (inter-vlan routing)
where does L2 switching occur?
between interfaces that are assigned to L2 VLANs or L2 trunks
Where does layer 3 switching occur?
between any type of interface as long as the interface can have an L3 address assigned
what is an SVI?
Switched Virtual Interface - an L3 address can be assigned to a logical interface that represents an entire VLAN, which becomes the DGW for that VLAN
By default, what layer do catalyst switchports operate on?
L2
if the switchport is part of an etherchannel, where is the network assigned
to the virtual port-channel interface
what must be done on an SVI before it is activated?
no shut
What is the traditional MLS view of switching?
route once, switch many
what does the RP do?
receives the first packet of a traffic flow and routes it
what does the SP do?
listens to the first packet going to router and away from the router. If it can switch in both directions, it learns a shortcut path so subsequent packets can be switched without the RP
How does the CEF L3 engine operate?
it’s a router that maintains routes (static or dynamic), and populates the FIB
What contains the next-hop entries?
FIB
what does the version number indicate when looking at CEF entries?
the number of times the entry has been updated since the table was generated
what does the epoch number indicate when looking at cef entries?
the number of times the CEF table has bee flushed and regenerated as a whole
what is a CEF punt?
a packet can’t be switched in hardware with the FIB and must go to the L3 engine
what is accelerated CEF (aCEF)?
CEF is distributed across multiple L3 forwarding engines, typically on Catalyst 6500 line cards each having only a subset
what I s distributed CEF (dCEF)?
CEF is distributed completely among multiple L3 forwarding engines.
what is the adjacency table?
a router keeps a routing table and an ARP table. The FIB combines them for every next-hop entry
what is a CEF glean?
the L3 forwarding engine can’t forward the packet in hardware because there is no L2 next-hop address, so the packet is sent to the L3 engine to generate the ARP response
what is arp throttling?
during the time that the FIB entry is in CEF glean waiting for ARP entries, subsequent packet to that host are dropped to keep input queues from filling
what is a null adjacency?
used to switch packets destined for the null interface
what is a drop adjacency?
used to switch packets that can’t be forwarded normallly due to an encapsulation failure, unresolved address, unsupported protocol, etc.
what is a discard adjacency?
packets are discarded due to an ACL or policy action
what is a punt adjacency?
packets must be sent to the L3 engine for further processing
what does the rewrite engine do?
it updates the L2 headers with the proper src and dst MAC, L3 TTL, L3 checksum, and L2 checksum information
How do you enable CEF?
it is enabled by default on all CEF capable switches
What are the 4 steps in DHCP negotiation?
1-client sends DHCP discover as broadcast, 2-DHCP server sends DHCP offer, client sends DHCP Request, DHCP server sends DHCP ack
How do you configure a DHCP gateway?
first configure a L3 interface in same VLAN as clients, then use the ip helper-address command to ID the DHCP server
What are the characteristics of the access layer?
low cost, high density ports, multiple scalable uplinks, vlans, traffic and protocol filtering and QoS
What are the characteristics of the distribution layer?
aggregation, high L3 throughput, security and policy based connectivity functions through access lists and packet filters, QoS, scalable high-speed links
what are the characteristics of the core layer
Very high L3 throughput, no access lists or port filtering, redundancy and resilience, advanced QoS
What is the core block?
the campus network’s backbone
What is the switch block?
Two distribution switches that aggregate one or more access switches
Where should multilayer switches be implemented?
Distribution layer
How far chould a VLAN extend?
Distribution layer
What criteria are used to size a switch block?
traffic types and patterns, amount of L3 switching cap. At dist. Layer, # users at access layer, geography, size of spanning tree domains
How many users should be within a switch block?
roughly 2000
How can you tell if a switch block is too large?
Routers at the distribution layer become the bottlenecks or broadcast or multicast traffic slows the switches in the switch block
What is the access layer best practice?
All L2 connectivity should be contained within the access layer.
What is the distribution layer best practice?
The distribution layer should have only L3 links
