一,交换相关(扩展部分)
1
,
DTP
(动态
trunk协议)
协商
2
,
VLAN
排错
1
)
VLAN
数据库中一定要有
VLAN-ID
-----正确状态:
SW#
show interfaces f0/1 switchport
Name: Fa0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN:
2 (test)
SW#show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/2, Fa0/3, Fa0/4, Fa0/5
Fa0/6, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/11, Fa0/12, Fa0/13
Fa0/14, Fa0/15, Fa0/16, Fa0/17
Fa0/18, Fa0/19, Fa0/20, Fa0/21
Fa0/22, Fa0/23, Fa0/24
2 test active Fa0/1
----VLAN 数据库中缺少VLAN-ID
SW#
show interfaces f0/1 switchport
Name: Fa0/1
Switchport: Enabled
Administrative Mode: static access
Operational Mode: down
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN:
2 (Inactive)
!
interface FastEthernet0/1 ----即使接口配置正确,VLAN依然无法使用
switchport access vlan 2
switchport mode access
!
SW#
sh mac address-table dynamic
Mac Address Table
-------------------------------------------
Vlan Mac Address Type Ports
---- ----------- -------- -----
3
00e0.f9b5.d3a1 DYNAMIC
Fa0/1
3
,构建冗余的
2
层网络拓扑
STP
(生成树)
公有协议:
802.1D----标准生成树
802.1W----快速生成树(rapid STP)
802.1S-----多生成树(MSTP)
思科私有:
PVST----
基于每
VLAN
的生成树(只支持
ISL
的封装)
PVST+---基于每VLAN
的生成树(
ISL/DOT1Q
)
Rapid-PVST+----快速的基于每VLAN的生成树
MIST----多实例生成树
Cisco交换机只能支持如下三种模式:
PVST+(IOS交换机默认)
Rapid PVST+(Nexus交换机默认)
MST(公有标准)(CCNP介绍)
1
)设备角色
a
,根桥(交换机)
---一个2层网络有且只有一个根桥
b
,非根桥(交换机)
----除根交换机以外,所有交换机皆被称为非根交换机
2
)端口角色
a,RP(根端口)----每个非根交换机上有且只有一个RP
b
,
DP
(指定端口)
---每个segement(链路)上有且只有一个DP
c,引入一个接口状态block---除了RP/DP以外,所有的接口皆处于Block(阻塞)状态
3
)
BPDU
(桥协议数据单元)
2111 848 22222
15:26:40.664: STP:
enc
01 80 C2 00 00 00 AA BB CC 00 11 30 00 26 42 42 03
*Mar 31 15:26:40.664: STP:
Data
00000000008003AABBCC001100000000008003AABBCC00110080040000140002000F00
链路开销:
10Gb/s开销为2
1Gb/s开销为4
100Mb/s开销为19
10Mb/s开销为100