MLS Flashcards
What does L3 switching allow you to avoid?
Router-on-a-stick. Reduces points of failure and saves bandwith.
What are the two flavors of Cisco’s catalyst switch-route software?
MLS (multilayer switching) and CES (Cisco express forwarding)
What are ASICs responsible for in L3 switching?
The same as in layer two–sending info out the correct port, and rewriting the source/destination MAC address.
What information does the TCAM table hold?
ACLs, next-hop routes, and QOS info.
How does MLS work?
With route-caching. The first packet in a flow is routed by the switch processor, while the rest in the flow are sent through ASICs.
What does “packet flow” mean?
A unidirectional stream of packets to a single destination, all part of the same protocol.
How does CEF work?
By having the hardware route all packets, saving CPU resources. This is accomplished with FIB and AT.
What’s the FIB?
Forwarding information database. Contains all of the information that the IP routing table does, but in a format usable by ASICs.
What is more common, CEF or MLS?
CEF, and it’s newer.
What’s the AT?
Adjacency table. Contains next-hop layer 2 information learned through ARP.
In CEF L3 switching, how is excessive information handled after the AT and TCAM tables are filled?
It’s processed by the routing engine.
Does CEF or MLS need to be configured?
No, but IP routing must be enabled.
What must be enabled for a switch to act as a default gateway?
IP routing.
What is a requirement for an SVI to be active?
It must be tagged/untagged on at least one port.
What does each layer 3 segment require to be utilized?
Some kind of route or routing protocol.
