Topologi
Objective
- Configure inter-VLAN routing using an external router, also known as a router on a stick.
Background
Inter-VLAN routing using an external router can be a cost-effective solution when it is necessary to segment a network into multiple broadcast domains. In this lab, you split an existing network into two separate VLANs on the access layer switches, and use an external router to route between the VLANs. An 802.1Q trunk connects the switch and the Fast Ethernet interface of the router for routing and management. Static routes are used between the gateway router and the ISP router. The switches are connected via an 802.1Q EtherChannel link.
Genomförande
För omväxlingsskull kan vi väl börja med routrarna den här gången. ISP
1
2
3
4
5
6
7
8
9
10
11
Router(config)#hostname ISP
ISP(config)#line con 0
ISP(config-line)#logging synchro
ISP(config-line)#exit
ISP(config)#int lo0
ISP(config-if)#ip add 200.200.200.1 255.255.255.0
ISP(config-if)#int s0/0/0
ISP(config-if)#ip add 192.168.1.2 255.255.255.0
ISP(config-if)#no shut
ISP(config-if)#exit
ISP(config)#ip route 0.0.0.0 0.0.0.0 s0/0/0 192.168.1.1
Gateway
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Router(config)#hostname Gateway
Gateway(config)#line con 0
Gateway(config-line)#logging sync
Gateway(config-line)#int s0/0/0
Gateway(config-if)#ip add 192.168.1.1 255.255.255.0
Gateway(config-if)#no shut
Gateway(config-if)#clock rate 256000
Gateway(config-if)#exit
Gateway(config)#ip route 0.0.0.0 0.0.0.0 s0/0/0 192.168.1.2
Gateway(config)#do ping 200.200.200.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 200.200.200.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/8/8 ms
Vi kan väl vänta lite med att sätta upp Intervlan-routingen tills vi är klara med grundkonfigen så vi fortsätter med S1 och S3 istället. S1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Switch(config)#hostname S1
S1(config)#line con 0
S1(config-line)#logging sync
S1(config-line)#exit
S1(config)#int range fa0/3 - 4
S1(config-if-range)#switchport trunk encaps dot1q
S1(config-if-range)#switchport mode dynamic desirable
S1(config-if-range)#description to S3
S1(config-if-range)#channel-protocol pagp
S1(config-if-range)#channel-group 1 mode desirable
Creating a port-channel interface Port-channel 1
S1(config-if-range)#int vlan 1
% Command exited out of interface range and its sub-modes.
Not executing the command for second and later interfaces
S1(config-if)#ip add 172.16.1.2 255.255.255.0
S1(config-if)#no shut
S1(config-if)#exit
S1(config)#ip default-gateway 172.16.1.1
S1(config)#vlan 100,200
S3
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Switch(config)#hostname S3
S3(config)#line con 0
S3(config-line)#logging sync
S3(config-line)#exit
S3(config)#int range fa0/3 - 4
S3(config-if-range)#switchport trunk encaps dot1q
S3(config-if-range)#switchport mode dynamic auto
S3(config-if-range)#channel-protocol pagp
S3(config-if-range)#channel-group 1 mode auto
Creating a port-channel interface Port-channel 1
S3(config-if-range)#description to S1
S3(config-if-range)#int vlan 1
% Command exited out of interface range and its sub-modes.
Not executing the command for second and later interfaces
S3(config-if)#ip add 172.16.1.3 255.255.255.0
S3(config-if)#no shut
S3(config-if)#exit
S3(config)#ip default-gateway 172.16.1.1
S3(config)#vlan 100,200
Då var det dags att konfa upp Inter-VLAN routing. För att kunna använda oss av subinterface för varje vlan (1, 100, 200) behöver vi aktivera trunking mellan S1 & Gateway. Observera att vi ej kan använda DTP-negotiaton när det är en router vi ansluter till (inget stöd för DTP). S1
1
2
3
4
5
6
7
8
9
S1(config)#int fa0/5
S1(config-if)#switchport trunk encapsulation dot1q
S1(config-if)#switchport mode trunk
S1(config-if)#description to Gateway
S1(config-if)#spanning-tree portfast trunk
%Warning: portfast should only be enabled on ports connected to a single
host. Connecting hubs, concentrators, switches, bridges, etc... to this
interface when portfast is enabled, can cause temporary bridging loops.
Use with CAUTION
Gateway
1
2
3
4
5
6
7
8
9
10
11
12
13
Gateway(config)#int fa0/1
Gateway(config-if)#description to S1
Gateway(config-if)#no shut
Gateway(config-if)#inte fa0/1.1
Gateway(config-subif)#encapsulation dot1q 1 native
Gateway(config-subif)#ip add 172.16.1.1 255.255.255.0
Gateway(config-subif)#inte fa0/1.100
Gateway(config-subif)#encapsulation dot1q 100
Gateway(config-subif)#ip add 172.16.100.1 255.255.255.0
Gateway(config-subif)#inte fa0/1.200
Gateway(config-subif)#encapsulation dot1q 200
Gateway(config-subif)#ip add 172.16.200.1 255.255.255.0
Gateway(config-subif)#end
Klart! Vi kan verifera med att pinga mellan S3 & ISPs loopback t.ex.:
1
2
3
4
5
S3#ping 200.200.200.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 200.200.200.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 8/209/1015 ms