Forwarding Information Base (FIB)—Contains routing and next-hop information. Lookups are performed according to longest-match IP prefix.
Adjacency table—Contains Layer 2 address information for next-hop FIB entries that are one hop away.
Packet rewrite—Hardware dedicated to rewriting the Layer 2 and Layer 3 header information of outbound packets after the forwarding decisions have been made.
Table 12-3 Fallback Bridging Configuration Commands
Task | Command Syntax |
Define a fallback bridge group | Switch(config)# bridge-group bridge-group protocol vlan-bridge |
Assign an interface to a bridge group | Switch(config)# interface vlan vlan-id Switch(config-if)# bridge-group bridge-group |
Table 12-4 Multilayer Switching Verification Commands
Task | Command Syntax |
Show a Layer 2 port status | Switch# show interface type mod/num switchport |
Show a Layer 3 port status | Switch# show interface type mod/num |
Show an SVI status | Switch# show interface vlan vlan-id |
View the FIB contents | Switch# show ip cef |
View FIB information for an interface | Switch# show ip cef [type mod/num | vlan vlan-id] [detail] |
View FIB information for an IP prefix | Switch# show ip cef [prefix-ip prefix-mask] [longer-prefixes] [detail] |
View FIB adjacency information | Switch# show adjacency [type mod/num | vlan vlan-id] [summary | detail] |
View counters for packets not switched by CEF | Switch# show cef not-cef-switched |
Show fallback bridge group status | Switch# show bridge group |
Show fallback bridging table contents | Switch# show bridge bridge-group |
Q&A
The questions and scenarios in this book are more difficult than what you should experience on the actual exam. The questions do not attempt to cover more breadth or depth than the exam; however, they are designed to make sure that you know the answers. Rather than allowing you to derive the answers from clues hidden inside the questions themselves, the questions challenge your understanding and recall of the subject. Hopefully, these questions will help limit the number of exam questions on which you narrow your choices to two options and then guess.
You can find the answers to these questions in Appendix A.
What might you need to implement interVLAN routing?
Can interVLAN routing be performed over a single trunk link?
To configure an SVI, what commands are needed?
What command can verify the VLAN assignments on a Layer 2 port?
A switch has the following interface configurations in its running configuration:
interface fastethernet 0/1 switchport access vlan 5 ! interface vlan 5 ip address 192.168.10.1 255.255.255.0 no shutdown
What is necessary for packets to get from the FastEthernet interface to the VLAN 5 SVI?
What is the source of FIB information?
How often is the FIB updated?
What is meant by the term CEF punt?
What happens to the FIB when distributed CEF (dCEF) is used?
What happens during a CEF glean process?
What does a multilayer switch do to the IP TTL value just before a packet is forwarded?
What is fallback bridging?
Is it possible for an SVI to go down? If so, for what reasons?
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