Switching Notes
Layer 2
ACL –> Frame allowed / denied
QoS –> Priority frame marking
CAM –> next-hop information -> exit interface
|
|–> All three operations are performed at the same time using dedicated co-processors (ASICs)
Terney Content Addressable Memory
– 3 values (VMR)
– Value
– Mask
– Result
If destination is starting with 10.x.x.x, then deny
– 10.x.x.x –> Value
– 0.255.255.255 –> Mask
– Deny –> Result
show mac address-table
–> Vlan
–> MAC address
–> Type (how learned)
–> Ports (exit interface)
Layer 3
FIB –> Forwarding Information Base
PR –> Packet Rewrite
CEF –> Cisco Express Forwarding
PR
– rewrite TTL (IP headers)
– MAC source / destination
– IP checksum
– ethernet CRC
show ip cef
-> Prefix
-> Next-hop
-> no route
-> receive
-> drop
-> Interface
Switching is all about interfaces
Interface Modes
-> Access – connected to end devices
-> Trunk – connected to other switches
-> Tunnel – Q in Q tunnel
int fa0/1
switchport mode { access | trunk }
Tunnel mode is configured in access mode
int range fa0/1 – 5
int range fa0/1, fa0/5 – 8 , fa0/15
define interface ABC fa0/1, fa0/5 – 8
int range macro ABC
Trunking
-> ISL – Inter-Switch Link
-> 802.1Q – IEEE standard
ISL
-> not in the R&S v5 lab
-> Cisco proprietary
-> 30 bytles additionally added to the frame
——————–
| 26 | frame | 4 |
———————
-> only 15 bits used to identify the VLAN
-> no untagged VLAN
802.1Q
-> 4 bytes added to the frame
6 6 4 up to 1500 bytes 4
————————————————-
| DA | SA | .1q | type | data………| FCS |
————————————————-
^
-> 12 bits
-> 2^12 VLANs –> 4096
0 to 4095
-> Vlan 0 (hidden system VLAN)
-> Vlan 4095 (hidden system VLAN)
-> Vlans 1 – 4094 usable
Normal frame
-> 1518 bytes
802.1Q frame
-> 1522 bytes
Vlan 1
-> Management VLAN
-> Default native VLAN
-> untagged VLAN
-> used for:
-> CDP packets
-> VTP packets
-> STP packets
-> Shutting down VLAN 1 only affects data traffic
-> All switching protocols use VLAN 1
VLANs 1002 – 1005
-> Tolken Ring VLANs
ISL
-> VLANs 1 – 1001
Reduced MAC Address feature
– One VLAN -> priority number + Base MAC address
– Configured with:
-> SW1(config)# spanning-tree extended system-id
-> Default configuration
-> Required to create more than 1001 VLANs
SW1
– priority number: 32768
– Base MAC address: 0001.0002.0003
– VLAN 10: 32768.0001.0002.0003
– VLAN 11: 32769.0001.0002.0003
Spanning Tree Protocol (801.2D)
-> used to prevent loops while maintaining redundancy
