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Example: Configuring Layer 3 Subinterfaces for a Distribution Switch and an Access Switch

Requirements

This example uses the following hardware and software components:

• For the distribution switch, one EX4200-24F switch. This model is designed to be used as a distribution switch for aggregation or collapsed core network topologies and in space-constrained data centers. It has twenty-four 1-Gigabit Ethernet fiber SFP ports and an EX-UM-2XFP uplink module with two 10-Gigabit Ethernet XFP ports.
• For the access switch, any Layer 2 switch that supports 802.1Q VLAN tags.
• Junos OS Release 9.2 or later for EX Series switches.

Before you connect the switches, make sure you have:

• Connected the two switches.
• Configured the necessary VLANs. See Configuring VLANs for EX Series Switches (CLI Procedure) or Configuring VLANs for EX Series Switches (J-Web Procedure).

Overview and Topology

In a large office with multiple buildings and VLANs, you commonly aggregate traffic from a number of access switches into a distribution switch. This configuration example shows a simple topology to illustrate how to connect a single Layer 2 access switch connected to multiple VLANs to a distribution switch, enabling traffic to pass between those VLANs.

In the example topology, the LAN is segmented into five VLANs, all associated with interfaces on the access switch. One 1-Gigabit Ethernet port on the access switch's uplink module connects to one 1-Gigabit Ethernet port on the distribution switch.

Table 1 lists the settings for the example topology.

Configuring the Access Switch Subinterfaces

CLI Quick Configuration

To quickly create and configure subinterfaces on the access switch, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. On the trunk interface of the access switch, enable VLAN tagging:
   [edit interfaces ge-0/1/0]
user@access-switch# set vlan-tagging
2. Bind vlan1's VLAN ID to the logical interface:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 0 vlan-id 101
3. Set vlan1's subinterface IP address:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 0 family inet address 1.1.1.1/24
4. Bind vlan2's VLAN ID to the logical interface:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 1 vlan-id 102
5. Set vlan2's subinterface IP address:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 1 family inet address 2.1.1.1/24
6. Bind vlan3's VLAN ID to the logical interface:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 2 vlan–id 103
7. Set vlan3's subinterface IP address:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 2 family inet address 3.1.1.1/24
8. Bind vlan4's VLAN ID to the logical interface:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 3 vlan-id 104
9. Set vlan4's subinterface IP address:
   [edit interfaces ge-0/1/0]
user@access-switch# set unit 3 family inet address 4.1.1.1/24
10. Bind vlan5's VLAN ID to the logical interface:
    [edit interfaces ge-0/1/0]
user@access-switch# set unit 4 vlan-id 105
11. Set vlan5's subinterface IP address:
    [edit interfaces ge-0/1/0]
user@access-switch# set unit 4 family inet address 5.1.1.1/24

Results

Check the results of the configuration:

Configuring the Distribution Switch Subinterfaces

CLI Quick Configuration

To quickly create and configure subinterfaces on the distribution switch, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. On the trunk interface of the distribution switch, enable VLAN tagging:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set vlan-tagging
2. Bind vlan1's VLAN ID to the logical interface:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 0 vlan-id 101
3. Set vlan1's subinterface IP address:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 0 family inet address 1.1.1.2/24
4. Bind vlan2's VLAN ID to the logical interface:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 1 vlan-id 102
5. Set vlan2's subinterface IP address:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 1 family inet address 2.1.1.2/24
6. Bind vlan3's VLAN ID to the logical interface:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 2 vlan-id 103
7. Set vlan3's subinterface IP address:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 2 family inet address 3.1.1.2/24
8. Bind vlan4's VLAN ID to the logical interface:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 3 vlan-id 104
9. Set vlan4's subinterface IP address:
   [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 3 family inet address 4.1.1.2/24
10. Bind vlan5's VLAN ID to the logical interface:
    [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 4 vlan-id 105
11. Set vlan5's subinterface IP address:
    [edit interfaces ge-0/0/0]
user@distribution-switch# set unit 4 family inet address 5.1.1.2/24

Results

Verification

To confirm that the configuration is working properly, perform these tasks:

• Verifying That Subinterfaces Were Created
• Verifying That Traffic Passes Between VLANs

Verifying That Subinterfaces Were Created

Purpose

Verify that the subinterfaces were properly created on the access switch and distribution switch.

Action

1. Use the show interfaces command on the access switch:
   user@access-switch> show interfaces ge-0/1/0 terse

   Interface              Admin Link Proto    Local                 Remote
   ge-0/1/0               up    up
   ge-0/1/0.0             up    up   inet     1.1.1.1/24
   ge-0/1/0.1             up    up   inet     2.1.1.1/24
   ge-0/1/0.2             up    up   inet     3.1.1.1/24
   ge-0/1/0.3             up    up   inet     4.1.1.1/24
   ge-0/1/0.4             up    up   inet     5.1.1.1/24
   ge-0/1/0.32767         up    up
   

2. Use the show interfaces command on the distribution switch:
   user@distribution-switch> show interfaces ge-0/0/0 terse

   Interface              Admin Link Proto    Local                 Remote
   ge-0/0/0               up    up
   ge-0/0/0.0             up    up   inet     1.1.1.2/24
   ge-0/0/0.1             up    up   inet     2.1.1.2/24
   ge-0/0/0.2             up    up   inet     3.1.1.2/24
   ge-0/0/0.3             up    up   inet     4.1.1.2/24
   ge-0/0/0.4             up    up   inet     5.1.1.2/24
   ge-0/0/0.32767         up    up
   

Meaning

Each subinterface created is displayed as a ge-fpc/pic/port.x logical interface, where x is the unit number in the configuration. The status is listed as up, indicating the link is working.

Verifying That Traffic Passes Between VLANs

Purpose

Verify that the distribution switch is correctly routing traffic from one VLAN to another.

Action

1. From the access switch, ping the address of the vlan1 subinterface on the distribution switch:
   user@access-switch> ping 1.1.1.2 count 4

   PING 1.1.1.2 (1.1.1.2): 56 data bytes
   64 bytes from 1.1.1.2: icmp_seq=0 ttl=64 time=0.333 ms
   64 bytes from 1.1.1.2: icmp_seq=1 ttl=64 time=0.113 ms
   64 bytes from 1.1.1.2: icmp_seq=2 ttl=64 time=0.112 ms
   64 bytes from 1.1.1.2: icmp_seq=3 ttl=64 time=0.158 ms
   
   --- 1.1.1.2 ping statistics ---
   4 packets transmitted, 4 packets received, 0% packet loss
   round-trip min/avg/max/stddev = 0.112/0.179/0.333/0.091 ms

2. From the access switch, ping the address of the vlan2 subinterface on the distribution switch:
   user@access-switch> ping 2.1.1.2 count 4

   PING 2.1.1.2 (2.1.1.2): 56 data bytes
   64 bytes from 2.1.1.2: icmp_seq=0 ttl=64 time=0.241 ms
   64 bytes from 2.1.1.2: icmp_seq=1 ttl=64 time=0.113 ms
   64 bytes from 2.1.1.2: icmp_seq=2 ttl=64 time=0.162 ms
   64 bytes from 2.1.1.2: icmp_seq=3 ttl=64 time=0.167 ms
   
   --- 2.1.1.2 ping statistics ---
   4 packets transmitted, 4 packets received, 0% packet loss
   round-trip min/avg/max/stddev = 0.113/0.171/0.241/0.046 ms

3. From the access switch, ping the address of the vlan3 subinterface on the distribution switch:
   user@access-switch> ping 3.1.1.2 count 4

   PING 3.1.1.2 (3.1.1.2): 56 data bytes
   64 bytes from 3.1.1.2: icmp_seq=0 ttl=64 time=0.341 ms
   64 bytes from 3.1.1.2: icmp_seq=1 ttl=64 time=0.162 ms
   64 bytes from 3.1.1.2: icmp_seq=2 ttl=64 time=0.112 ms
   64 bytes from 3.1.1.2: icmp_seq=3 ttl=64 time=0.208 ms
   
   --- 3.1.1.2 ping statistics ---
   4 packets transmitted, 4 packets received, 0% packet loss
   round-trip min/avg/max/stddev = 0.112/0.206/0.341/0.085 ms
   

4. From the access switch, ping the address of the vlan4 subinterface on the distribution switch:
   user@access-switch> ping 4.1.1.2 count 4

   PING 4.1.1.2 (4.1.1.2): 56 data bytes
   64 bytes from 4.1.1.2: icmp_seq=0 ttl=64 time=0.226 ms
   64 bytes from 4.1.1.2: icmp_seq=1 ttl=64 time=0.166 ms
   64 bytes from 4.1.1.2: icmp_seq=2 ttl=64 time=0.107 ms
   64 bytes from 4.1.1.2: icmp_seq=3 ttl=64 time=0.221 ms
   
   --- 4.1.1.2 ping statistics ---
   4 packets transmitted, 4 packets received, 0% packet loss
   round-trip min/avg/max/stddev = 0.107/0.180/0.226/0.048 ms

5. From the access switch, ping the address of the vlan5 subinterface on the distribution switch:
   user@access-switch> ping 5.1.1.2 count 4

   PING 5.1.1.2 (5.1.1.2): 56 data bytes
   64 bytes from 5.1.1.2: icmp_seq=0 ttl=64 time=0.224 ms
   64 bytes from 5.1.1.2: icmp_seq=1 ttl=64 time=0.104 ms
   64 bytes from 5.1.1.2: icmp_seq=2 ttl=64 time=0.102 ms
   64 bytes from 5.1.1.2: icmp_seq=3 ttl=64 time=0.170 ms
   
   --- 5.1.1.2 ping statistics ---
   4 packets transmitted, 4 packets received, 0% packet loss
   round-trip min/avg/max/stddev = 0.102/0.150/0.224/0.051 ms

Meaning

If all the ping packets are transmitted and are received by the destination address, the subinterfaces are up and working.