Cisco WS-X6248-RJ-45 - Catalyst 6000 Expansion Module Instrukcja Użytkownika Pobierz pdf (Strona 17)

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information such as an IP subnet or IPX network number. If a particular Layer 2 VLAN does not have an associated

SVI created, then trafﬁc will be bridged in that VLAN but not routable to or from that VLAN. As switch ports

are added and removed from various VLANs, they automatically participate in the Layer 3 environment

created by the appropriate SVI. For managing a device in Cisco IOS Software, the SVI requires an IP address for

network reachability.

Access Switchport

An access switchport is a Layer 2 port that belongs to only one VLAN. For conﬁguration, the switchport command

is used to convert an interface from the default routed interface to a Layer 2 interface. In converting the port from a

Layer 3 port to a Layer 2 port, Layer 2 features, including DTP and STP, are enabled. This single switchport

command must be enabled before any other switch port-related conﬁguration is allowed. Like port operation in

CatOS, switchports automatically default to VLAN 1. To statically create an access port (one that will not attempt

to negotiate a trunk), enter the switchport mode access command from the interface conﬁguration. Then use the

switchport access vlan <vlan-id> command to assign the access port to a particular VLAN. The following example

deﬁnes port 5/1 as an access port in VLAN2.

Trunk Switchport

Trunk switchports in Cisco IOS Software are Layer 2 ports that carry multiple VLANs using ISL or IEEE 802.1q

encapsulations. They are fully compatible with any other device supporting the ISL or IEEE 802.1q protocols.

After converting a routed interface to a Layer 2 switchport, the switchport will default to switchport mode dynamic

desirable. The port is capable of forming a trunk with a neighboring Layer 2 device by using DTP for negotiating a

trunk. If the neighboring interface supports trunking and is conﬁgured to allow trunking, the link becomes a Layer

2 trunk when you enter the switchport command (due to the dynamic/desirable default). By default, trunks negotiate

encapsulation: if the neighboring interface supports bothISL andIEEE 802.1qencapsulation andboth interfacesare

set to negotiate the encapsulation type, the trunk will use ISL encapsulation. This is the same operation as in CatOS.

The following example shows how to conﬁgure a trunk for IEEE 802.1q encapsulation.

IOS# configure terminal

IOS(Config)# interface fastethernet5/1

IOS(Config-if)# switchport

IOS(Config-if)# switchport mode access

IOS(Config-if)# switchport access vlan 2

IOS(Config-if)# no shut

IOS(Config-if)# end

IOS# configure terminal

IOS(Config)# interface fastethernet 5/1

IOS(Config-if)# switchport

IOS(Config-if)# switchport trunk encapsulation dot1q

IOS(Config-if)# end

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Cisco WS-X6248-RJ-45 - Catalyst 6000 Expansion Module Instrukcja Użytkownika Strona 17