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Example: Configuring DHCP Relay on MC- LAG with VRRP on an EX9200 Switch

Requirements

• Junos OS Release 12.3 or later for EX Series
• Two EX9200 switches

• Configure MC-LAG and verify that MC-LAG and ICCP is up and running

To complete the configuration, enable VRRP by completing the following steps for each MC-LAG:

• Create a Integrated Routing and Bridging (IRB) interface
• Create a VRRP group and assign a virtual IP address that is shared between each switch in the VRRP group
• Enable a member of a VRRP group to accept all packets destined for the virtual IP address if it is the master in the VRRP group
• Configure Layer 3 connectivity between the VRRP groups

Overview

In this example, you configure DHCP relay with MC-LAG across two switches, consisting of two EX9200 switches, an interchassis control link-protection link (ICL-PL), multichassis protection link for the ICL-PL, ICCP for the peers hosting the MC-LAG, and Layer 3 connectivity between MC-LAG peers. Layer 3 connectivity is required for ICCP.

Note: On EX9200 switches, dynamic ARP resolution is not supported over inter-chassis control links (ICLs). As a workaround, you can configure static ARP on both ends of the ICL.

Topology

Configuration

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them in a text file, remove any line breaks, change any details necessary to match your network configuration, and paste the commands into the CLI at the [edit forwarding-options] hierarchy level of Switch A.

To quickly configure this example, copy the following commands, paste them in a text file, remove any line breaks, change any details necessary to match your network configuration, and paste the commands into the CLI at the [edit forwarding-options] hierarchy level of Switch B.

Step-by-Step Procedure

1. Configure forward snooped (unicast) packets on interfaces.
   [edit]

   set forwarding-options dhcp-relay forward-snooped-clients all-interfaces
2. Create a DHCP server group, which is a group of 1 through 5 DHCP server IP addresses:
   set forwarding-options dhcp-relay server-group GVP-DHCP 10.168.61.5
3. Allow the creation of a binding entry using snooped (unicast) clients:
   set forwarding-options dhcp-relay overrides allow-snooped-clients
4. Apply a DHCP relay agent configuration to the named group of DHCP server addresses:
   set forwarding-options dhcp-relay active-server-group GVP-DHCP
5. Create a DHCP relay group that includes at least one interface. DHCP relay runs on the interfaces defined in DHCP groups:
   set forwarding-options dhcp-relay group Floor1 interface irb.2540
6. Configure the relay agent to suppress the installation of ARP and route entries for corresponding client binding:
   set forwarding-options dhcp-relay route-suppression destination

Step-by-Step Procedure

1. Configure forward snooped (unicast) packets on interfaces.
   [edit]

   set forwarding-options dhcp-relay forward-snooped-clients all-interfaces
2. Create a DHCP server group, which is a group of 1 through 5 DHCP server IP addresses:
   set forwarding-options dhcp-relay server-group GVP-DHCP 10.168.61.5
3. Allow the creation of a binding entry using snooped (unicast) clients:
   set forwarding-options dhcp-relay overrides allow-snooped-clients
4. Apply a DHCP relay agent configuration to the named group of DHCP server addresses:
   set forwarding-options dhcp-relay active-server-group GVP-DHCP
5. Create a DHCP relay group that includes at least one interface. DHCP relay runs on the interfaces defined in DHCP groups:
   set forwarding-options dhcp-relay group Floor1 interface irb.2540
6. Configure the relay agent to suppress the installation of ARP and route entries for corresponding client binding:
   set forwarding-options dhcp-relay route-suppression destination

Results

Display the results of the configuration on Switch A.

Display the results of the configuration on Switch B.

Overwriting Address Information

Step-by-Step Procedure

1. Specify that you want to configure override options.
   [edit forwarding-options dhcp-relay]
user@host# edit overrides
2. Specify that the address of DHCP packets is overwritten.
   [edit forwarding-options dhcp-relay overrides]
user@host# set always-write-giaddr

Verification

• Check whether DHCP Relay Binding is happening
• Check whether relay statistics are being displayed

Check whether DHCP Relay Binding is happening

Purpose

To check whether address bindings in the Dynamic Host Configuration Protocol (DHCP) client table are being displayed.

Action

Client IP Address:  10.168.103.20
Hardware Address:             84:18:88:a8:ca:80
State:            BOUND(RELAY_STATE_BOUND)
Lease Expires:                2013-10-03 12:17:43 CEST
Lease Expires in:             85829 seconds
Lease Start:                  2013-10-02 10:48:34 CEST
Last Packet Received:         2013-10-02 12:17:43 CEST
Incoming Client Interface:    ae0.0(irb.2540)
Server Ip Address:            10.168.61.5
Server Interface:             none
Bootp Relay Address:          10.168.103.2
Session Id:                   29

Client IP Address:  10.168.103.20
Hardware Address:             84:18:88:a8:ca:80
State:            BOUND(RELAY_STATE_BOUND)
Lease Expires:                2013-10-03 12:17:43 CEST
Lease Expires in:             86228 seconds
Lease Start:                  2013-10-02 10:48:34 CEST
Last Packet Received:         2013-10-02 10:48:34 CEST
Incoming Client Interface:    ae11.0(irb.2540)
Server Ip Address:            10.168.61.5
Server Interface:             none
Bootp Relay Address:          10.168.103.2
Session Id:                   16

Meaning

The field State indicates the state of DHCP relay address binding table on the DHCP client. The state BOUND indicates that the client has an active IP address lease.

Check whether relay statistics are being displayed

Purpose

To check whether DHCP relay statistics are being displayed.

Action

Packets dropped:
	Total                      9
	dhcp-service total         9
Messages received:
    BOOTREQUEST                4
    DHCPDECLINE                0
    DHCPDISCOVER               1
    DHCPINFORM                 0
    DHCPRELEASE                0
    DHCPREQUEST                3

Messages sent:
    BOOTREPLY                  0
    DHCPOFFER                  0
    DHCPACK                    0
    DHCPNAK                    0
    DHCPFORCERENEW             0

Meaning

The field Total displays the total number of packets discarded by the extended DHCP relay agent application.