3.4.5 Packet Tracer - Configure Trunks Answers
Topology
3.4.5 Packet Tracer - Configure Trunks
Addressing Table
| Device | Interface | IP Address | Subnet Mask | Switch Port | VLAN |
|---|---|---|---|---|---|
| PC1 | NIC | 172.17.10.21 | 255.255.255.0 | S2 F0/11 | 10 |
| PC2 | NIC | 172.17.20.22 | 255.255.255.0 | S2 F0/18 | 20 |
| PC3 | NIC | 172.17.30.23 | 255.255.255.0 | S2 F0/6 | 30 |
| PC4 | NIC | 172.17.10.24 | 255.255.255.0 | S3 F0/11 | 10 |
| PC5 | NIC | 172.17.20.25 | 255.255.255.0 | S3 F0/18 | 20 |
| PC6 | NIC | 172.17.30.26 | 255.255.255.0 | S3 F0/6 | 30 |
Objectives
- Part 1: Verify VLANs
- Part 2: Configure Trunks
Background
Trunks are required to pass VLAN information between switches. A port on a switch is either an access port or a trunk port. Access ports carry traffic from a specific VLAN assigned to the port. A trunk port by default is a member of all VLANs. Therefore, it carries traffic for all VLANs. This activity focuses on creating trunk ports and assigning them to a native VLAN other than the default.
Instructions
Part 1: Verify VLANs
Step 1: Display the current VLANs.
a. On S1, issue the command that will display all VLANs configured. There should be ten VLANs in total. Notice that all 26 access ports on the switch are assigned to VLAN 1.
S1# show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, 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
Gig0/1, Gig0/2
10 Faculty/Staff active
20 Students active
30 Guest(Default) active
88 Management active
99 Native active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default activeb. On S2 and S3, display and verify that all the VLANs are configured and assigned to the correct switch ports according to the Addressing Table.
S2# show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/12, Fa0/13, Fa0/14
Fa0/15, Fa0/16, Fa0/17, Fa0/19
Fa0/20, Fa0/21, Fa0/22, Fa0/23
Fa0/24, Gig0/1, Gig0/2
10 Faculty/Staff active Fa0/11
20 Students active Fa0/18
30 Guest(Default) active Fa0/6
88 Management active
99 Native active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default activeS3# show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/12, Fa0/13, Fa0/14
Fa0/15, Fa0/16, Fa0/17, Fa0/19
Fa0/20, Fa0/21, Fa0/22, Fa0/23
Fa0/24, Gig0/1, Gig0/2
10 Faculty/Staff active Fa0/11
20 Students active Fa0/18
30 Guest(Default) active Fa0/6
88 Management active
99 Native active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default activeStep 2: Verify loss of connectivity between PCs on the same network.
Ping between hosts on the same VLAN on the different switches. Although PC1 and PC4 are on the same network, they cannot ping one another. This is because the ports connecting the switches are assigned to VLAN 1 by default. In order to provide connectivity between the PCs on the same network and VLAN, trunks must be configured.
C:\> ping 172.17.10.24
Part 2: Configure Trunks
Step 1: Configure trunking on S1 and use VLAN 99 as the native VLAN.
a. Configure G0/1 and G0/2 interfaces on S1 for trunking.
S1(config)# interface range gigabitethernet 0/1 - 2 S1(config-if-range)# switchport mode trunk
b. Configure VLAN 99 as the native VLAN for G0/1 and G0/2 interfaces on S1.
S1(config-if-range)# switchport trunk native vlan 99
The trunk port takes a short time to become active due to Spanning Tree Protocol. Click Fast Forward Time to speed the process. After the ports become active, you will periodically receive the following syslog messages:
%CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/2 (99), with S3 GigabitEthernet0/2 (1). %CDP-4-NATIVE_VLAN_MISMATCH: Native VLAN mismatch discovered on GigabitEthernet0/1 (99), with S2 GigabitEthernet0/1 (1).
You configured VLAN 99 as the native VLAN on S1. However, S2 and S3 are using VLAN 1 as the default native VLAN as indicated by the syslog messages.
Although you have a native VLAN mismatch, pings between PCs on the same VLAN are now successful.
Explain.
Pings are successful because trunking has been enabled on S1. Dynamic Trunking Protocol (DTP) has automatically negotiated the other side of the trunk links. In this case, S2 and S3 have now automatically configured the ports attached to S1 as trunking ports.
Step 2: Verify trunking is enabled on S2 and S3.
On S2 and S3, issue the show interfaces trunk command to confirm that DTP has successfully negotiated trunking with S1 on S2 and S3. The output also displays information about the trunk interfaces on S2 and S3. You will learn more about DTP later in the course.
S2# show interfaces trunk Port Mode Encapsulation Status Native vlan Gig0/1 auto n-802.1q trunking 1 Port Vlans allowed on trunk Gig0/1 1-1005 Port Vlans allowed and active in management domain Gig0/1 1,10,20,30,88,99 Port Vlans in spanning tree forwarding state and not pruned Gig0/1 10,20,30,88
S3# show interfaces trunk Port Mode Encapsulation Status Native vlan Gig0/2 auto n-802.1q trunking 1 Port Vlans allowed on trunk Gig0/2 1-1005 Port Vlans allowed and active in management domain Gig0/2 1,10,20,30,88,99 Port Vlans in spanning tree forwarding state and not pruned Gig0/2 10,20,30,88
Which active VLANs are allowed to cross the trunk?
1,10,20,30,88,99
Step 3: Correct the native VLAN mismatch on S2 and S3.
a. Configure VLAN 99 as the native VLAN for the appropriate interfaces on S2 and S3.
S2(config)# interface gigabitethernet 0/1 S2(config-if)# switchport mode trunk S2(config-if)# switchport trunk native vlan 99
S3(config)# interface gigabitethernet 0/2 S3(config-if)# switchport mode trunk S3(config-if)# switchport trunk native vlan 99
b. Issue the show interfaces trunk command to verify the correct native VLAN configuration.
S2# show interfaces trunk
Port Mode Encapsulation Status Native vlan
Gig0/1 on 802.1q trunking 99
Port Vlans allowed on trunk
Gig0/1 1-1005
Port Vlans allowed and active in management domain
Gig0/1 1,10,20,30,88,99
Port Vlans in spanning tree forwarding state and not pruned
Gig0/1 1,10,20,30,88,99S3# show interfaces trunk
Port Mode Encapsulation Status Native vlan
Gig0/2 on 802.1q trunking 99
Port Vlans allowed on trunk
Gig0/2 1-1005
Port Vlans allowed and active in management domain
Gig0/2 1,10,20,30,88,99
Port Vlans in spanning tree forwarding state and not pruned
Gig0/2 1,10,20,30,88,99Step 4: Verify configurations on S2 and S3.
a. Issue the show interfaces interface switchport command to verify that the native VLAN is now 99.
S2# show interfaces gigabitethernet 0/1 switchport Name: Gig0/1 Switchport: Enabled Administrative Mode: trunk Operational Mode: trunk Administrative Trunking Encapsulation: dot1q Operational Trunking Encapsulation: dot1q Negotiation of Trunking: On Access Mode VLAN: 1 (default) Trunking Native Mode VLAN: 99 (Native) Voice VLAN: none Administrative private-vlan host-association: none Administrative private-vlan mapping: none Administrative private-vlan trunk native VLAN: none Administrative private-vlan trunk encapsulation: dot1q Administrative private-vlan trunk normal VLANs: none Administrative private-vlan trunk private VLANs: none Operational private-vlan: none Trunking VLANs Enabled: All Pruning VLANs Enabled: 2-1001 Capture Mode Disabled Capture VLANs Allowed: ALL Protected: false Unknown unicast blocked: disabled Unknown multicast blocked: disabled Appliance trust: none
S3# show interfaces gigabitethernet 0/2 switchport Name: Gig0/2 Switchport: Enabled Administrative Mode: trunk Operational Mode: trunk Administrative Trunking Encapsulation: dot1q Operational Trunking Encapsulation: dot1q Negotiation of Trunking: On Access Mode VLAN: 1 (default) Trunking Native Mode VLAN: 99 (Native) Voice VLAN: none Administrative private-vlan host-association: none Administrative private-vlan mapping: none Administrative private-vlan trunk native VLAN: none Administrative private-vlan trunk encapsulation: dot1q Administrative private-vlan trunk normal VLANs: none Administrative private-vlan trunk private VLANs: none Operational private-vlan: none Trunking VLANs Enabled: All Pruning VLANs Enabled: 2-1001 Capture Mode Disabled Capture VLANs Allowed: ALL Protected: false Unknown unicast blocked: disabled Unknown multicast blocked: disabled Appliance trust: none
b. Use the show vlan command to display information regarding configured VLANs.
S2# show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/12, Fa0/13, Fa0/14
Fa0/15, Fa0/16, Fa0/17, Fa0/19
Fa0/20, Fa0/21, Fa0/22, Fa0/23
Fa0/24, Gig0/2
10 Faculty/Staff active Fa0/11
20 Students active Fa0/18
30 Guest(Default) active Fa0/6
88 Management active
99 Native active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
<output omitted>S3# show vlan
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4
Fa0/5, Fa0/7, Fa0/8, Fa0/9
Fa0/10, Fa0/12, Fa0/13, Fa0/14
Fa0/15, Fa0/16, Fa0/17, Fa0/19
Fa0/20, Fa0/21, Fa0/22, Fa0/23
Fa0/24, Gig0/1
10 Faculty/Staff active Fa0/11
20 Students active Fa0/18
30 Guest(Default) active Fa0/6
88 Management active
99 Native active
1002 fddi-default active
1003 token-ring-default active
1004 fddinet-default active
1005 trnet-default active
<output omitted>Why is port G0/1 on S2 no longer assigned to VLAN 1?
Port G0/1 is now a trunk port, and trunk ports are not displayed in the show vlan output.
Device Configs - Final
SWITCH S1
! ============================================================== !--- 3.4.5 Packet Tracer - Configure Trunks !--- ANSWER SCRIPT FOR SWITCH S1 !--- Usage: copy this whole file and paste it into the S1 terminal (start at the S1> prompt). Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. !--- The VLANs and the access ports on S2/S3 are preconfigured; this lab only configures the trunk links. ! ============================================================== enable configure terminal ! -------------------------------------------------------------- !--- Part 2, Step 1: Configure trunking on S1 and use VLAN 99 as the native VLAN. ! -------------------------------------------------------------- !--- a. Configure G0/1 (to S2) and G0/2 (to S3) for trunking. !--- b. Configure VLAN 99 as the native VLAN on both trunks. CDP reports a native VLAN mismatch until S2 and S3 are also set to VLAN 99. interface range gigabitethernet 0/1 - 2 switchport mode trunk switchport trunk native vlan 99 exit end ! -------------------------------------------------------------- !--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- show interfaces trunk -> Gig0/1 and Gig0/2 trunking, native VLAN 99 !--- From PC1, ping 172.17.10.24 (PC4) -> success across the trunks ! ==============================================================
SWITCH S2
! ============================================================== !--- 3.4.5 Packet Tracer - Configure Trunks !--- ANSWER SCRIPT FOR SWITCH S2 !--- Usage: copy this whole file and paste it into the S2 terminal (start at the S2> prompt). Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. !--- S2 connects to S1 on G0/1 only. ! ============================================================== enable configure terminal ! -------------------------------------------------------------- !--- Part 2, Step 3: Correct the native VLAN mismatch on S2 and S3. ! -------------------------------------------------------------- !--- a. Make G0/1 a static trunk (Step 4 expects "Administrative Mode: trunk") and set the native VLAN to 99 to match S1. interface gigabitethernet 0/1 switchport mode trunk switchport trunk native vlan 99 exit end ! -------------------------------------------------------------- !--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- show interfaces trunk -> Gig0/1 trunking, native VLAN 99, VLANs 1,10,20,30,88,99 active !--- show interfaces gigabitethernet 0/1 switchport -> Administrative Mode: trunk, Native VLAN 99 !--- show vlan -> Gig0/1 no longer listed (trunk ports are not shown) ! ==============================================================
SWITCH S3
! ============================================================== !--- 3.4.5 Packet Tracer - Configure Trunks !--- ANSWER SCRIPT FOR SWITCH S3 !--- Usage: copy this whole file and paste it into the S3 terminal (start at the S3> prompt). Every line beginning with "!" is a comment; IOS ignores it, so pasting a comment by accident is harmless. !--- S3 connects to S1 on G0/2 only. ! ============================================================== enable configure terminal ! -------------------------------------------------------------- !--- Part 2, Step 3: Correct the native VLAN mismatch on S2 and S3. ! -------------------------------------------------------------- !--- a. Make G0/2 a static trunk (Step 4 expects "Administrative Mode: trunk") and set the native VLAN to 99 to match S1. interface gigabitethernet 0/2 switchport mode trunk switchport trunk native vlan 99 exit end ! -------------------------------------------------------------- !--- Save the configuration to NVRAM. (Press Enter when prompted for the destination filename.) ! -------------------------------------------------------------- copy running-config startup-config ! ============================================================== !--- Verification: !--- show interfaces trunk -> Gig0/2 trunking, native VLAN 99, VLANs 1,10,20,30,88,99 active !--- show interfaces gigabitethernet 0/2 switchport -> Administrative Mode: trunk, Native VLAN 99 !--- show vlan -> Gig0/2 no longer listed (trunk ports are not shown) ! ==============================================================
