Example for Configuring MLAG with DHCP Relay
- Tracy Yang (Unlicensed)
Networking Requirements
Figure 1. Example for Configuring MLAG with DHCP Relay
As shown in Figure 1, Switch 1 and Switch 2 are a pair of MLAG peers. DHCP client connects to Switch 3 which is dual-homed to the MLAG network. The DHCP client in network segment 10.20.20.0/24 wants to dynamically obtain IP address from the DHCP server which is in a different subnet. In this case, we need to configure DHCP relay on MLAG peers to forward DHCP packets between client and server.
When an MLAG is deployed to provide L3 routing functions to downstream clients, the MLAG peers should provide the same gateway address to the downstream clients. VRRP groups combine the MLAG peer devices into a virtual router and use the IP address of the VRRP virtual router to communicate with the access devices as the default gateway address.
Follow the configuration roadmap below to complete the example for configuring MLAG with DHCP relay:
- Configure Switch 1 and Switch 2 as an MLAG pair.
- Configure Active-Active VRRP on Switch1 and Switch2 as a virtual Gateway for DHCP client.
- Enable DHCP relay on Switch 1 and Switch 2.
- DHCP relay configuration should be identical on both MLAG peer devices.
- Configure DHCP relay agent IP address to use VRRP virtual IP.
    4. Configure a route to DHCP server on Switch 1 and Switch 2. The static route is used as an example.
    5. As a Layer 2 device, access Switch3 dual-accesses to the network through Switch1 and Switch2 by a LAG interface.
    6. Configure the DHCP client with a gateway address that is the IP address of the VRRP virtual router.
Procedure
Switch1
MLAG Configuration
Step1Â Â Â Â Â Â Â Â Â Configure the VLANs.
admin@Switch1# set vlans vlan-id 10 admin@Switch1# set vlans vlan-id 4088 l3-interface vlan4088 admin@Switch1# set interface aggregate-ethernet ae48 family ethernet-switching native-vlan-id 4088 admin@Switch1# set interface aggregate-ethernet ae48 family ethernet-switching port-mode trunk admin@Switch1# set interface aggregate-ethernet ae48 family ethernet-switching vlan members 10 admin@Switch1# set interface aggregate-ethernet ae71 family ethernet-switching port-mode trunk admin@Switch1# set interface aggregate-ethernet ae71 family ethernet-switching vlan members 10Â Â Â Â Â Â
Step2        Configure aggregation interfaces with LACP mode.      Â
admin@Switch1# set interface aggregate-ethernet ae71 aggregated-ether-options lacp enable true admin@Switch1# set interface aggregate-ethernet ae48 aggregated-ether-options lacp enable true
Step3Â Â Â Â Â Â Â Â Â Add member interfaces to the LAG.
admin@Switch1# set interface gigabit-ethernet te-1/1/1 ether-options 802.3ad ae48 admin@Switch1# set interface gigabit-ethernet te-1/1/2 ether-options 802.3ad ae48 admin@Switch1# set interface gigabit-ethernet te-1/1/41 ether-options 802.3ad ae71Â
Step4Â Â Â Â Â Â Â Â Configure an MLAG domain ID.
admin@Switch1# set protocols mlag domain 10
NOTE: Currently, only one MLAG domain is allowed to be configured on one MLAG device.
Step5Â Â Â Â Â Â Â Â Â Specify Switch1 as MLAG Node 0.
admin@Switch1# set protocols mlag domain 10 node 0
Step6         Configure the L3 interface IP address for peer link port on local MLAG peer device.      Â
admin@Switch1# set l3-interface vlan-interface vlan4088 address 10.10.0.1 prefix-length 24
Step7         Configure link ID for the MLAG member port.      Â
admin@Switch1# set protocols mlag domain 10Â interface ae71 link 1
NOTE: The paired MLAG member ports separately configured on two MLAG peer must be bound to the same MLAG link ID.
Step8Â Â Â Â Â Â Â Â Â Configure MLAG peer link and peer VLAN.
admin@Switch1# set protocols mlag domain 10 peer-ip 10.10.0.2 peer-link ae48 admin@Switch1# set protocols mlag domain 10 peer-ip 10.10.0.2 peer-vlan 4088
NOTE: Peer-link port should be configured as a LAG port.
VRRP Configuration
Step 1Â Â Â Â Configure the L3 interface IP address.
admin@Switch1# set l3-interface vlan-interface vlan10 address 11.251.201.1 prefix-length 24
Step 2 Â Enable Active-Active-VRRP function.
admin@Switch1# set protocols vrrp interface vlan10 vrid 100 ip 11.251.201.3 admin@Switch1# set protocols vrrp interface vlan10 vrid 100 load-balance disable false
DHCP Relay Configuration
Step 1Â Â Enable IP routing function when using DHCP relay.
admin@Switch1# set ip routing enable true
Step 2Â Â Enable the DHCP relay function on L3 VLAN interface vlan10.
admin@Switch1# set protocols dhcp relay interface vlan10 disable false
Step 3Â Â Configure the IP address of DHCP server 192.168.2.100.
admin@Switch1# set protocols dhcp relay interface vlan10 dhcp-server-address 192.168.2.100
Step 4Â Â Configure DHCP relay agent IP address to use VRRP virtual IP.
admin@Switch1# set protocols dhcp relay interface vlan10 relay-agent-address 11.251.201.3
Other Configuration
Step1Â Â Â Â Â Â Â Configure VLAN and VLAN interface.
admin@Switch1# set vlans vlan-id 20 admin@Switch1# set vlans vlan-id 20 l3-interface vlan20 admin@Switch1# set interface gigabit-ethernet te-1/1/42 family ethernet-switching native-vlan-id 20 admin@Switch1# set l3-interface vlan-interface vlan20 address 10.1.1.1 prefix-length 24
Step 2Â Â Configure route to DHCP server. The following command configures static route as an example.
admin@Switch1# set protocols static route 192.168.2.0/24 next-hop 10.1.1.2
Step 3 Â Commit the configuration.
admin@Switch1# commit
Switch2
MLAG Configuration
Step 1Â Â Â Â Â Â Â Configure the VLANs.
admin@Switch2# set vlans vlan-id 10 admin@Switch2# set vlans vlan-id 4088 l3-interface vlan4088 admin@Switch2# set interface aggregate-ethernet ae48 family ethernet-switching native-vlan-id 4088 admin@Switch2# set interface aggregate-ethernet ae48 family ethernet-switching port-mode trunk admin@Switch2# set interface aggregate-ethernet ae48 family ethernet-switching vlan members 10 admin@Switch2# set interface aggregate-ethernet ae71 family ethernet-switching port-mode trunk admin@Switch2# set interface aggregate-ethernet ae71 family ethernet-switching vlan members 10
Step 2    Configure aggregation interfaces with LACP mode. Â
admin@Switch2# set interface aggregate-ethernet ae71 aggregated-ether-options lacp enable true admin@Switch2# set interface aggregate-ethernet ae48 aggregated-ether-options lacp enable true
Step 3Â Â Â Â Â Â Add member interfaces to the LAG.
admin@Switch2# set interface gigabit-ethernet te-1/1/1 ether-options 802.3ad ae48 admin@Switch2# set interface gigabit-ethernet te-1/1/2 ether-options 802.3ad ae48 admin@Switch2# set interface gigabit-ethernet te-1/1/41 ether-options 802.3ad ae71Â
Step 4Â Â Â Â Â Configure an MLAG domain ID.Â
admin@Switch2# set protocols mlag domain 10
 NOTE: Currently, only one MLAG domain is allowed to be configured on one MLAG device.
Step 5Â Â Â Â Â Specify Switch2 as MLAG Node 1.
admin@Switch2# set protocols mlag domain 10 node 1
Step 6Â Â Â Configure the L3 interface IP address for peer link port on local MLAG peer device.
admin@Switch2# set l3-interface vlan-interface vlan4088 address 10.10.0.2 prefix-length 24
Step 7      Configure link ID for the MLAG member port.
admin@Switch2# set protocols mlag domain 10Â interface ae71 link 1
NOTE: The paired MLAG member ports separately configured on two MLAG peer must be bound to the same MLAG link ID.
Step 8Â Â Â Â Â Â Â Configure MLAG peer link and peer VLAN.
admin@Switch2# set protocols mlag domain 10 peer-ip 10.10.0.1 peer-link ae48 admin@Switch2# set protocols mlag domain 10 peer-ip 10.10.0.1 peer-vlan 4088
NOTE: Peer-link port should be configured as a LAG port.
VRRP Configuration
Step 1Â Â Â Â Â Configure the L3 interface IP address.
admin@Switch2# set l3-interface vlan-interface vlan10 address 11.251.201.2 prefix-length 24
Step 2Â Â Enable Active-Active-VRRP function.
admin@Switch2# set protocols vrrp interface vlan10 vrid 100 ip 11.251.201.3 admin@Switch2# set protocols vrrp interface vlan10 vrid 100 load-balance disable false
DHCP Relay Configuration
Step 1Â Â Enable IP routing function when using DHCP relay.
admin@Switch2# set ip routing enable true
Step 2Â Â Enable the DHCP relay function on L3 VLAN interface vlan10.
admin@Switch2# set protocols dhcp relay interface vlan10 disable false
Step 3Â Â Configure the IP address of DHCP server 192.168.2.100.
admin@Switch2# set protocols dhcp relay interface vlan10 dhcp-server-address 192.168.2.100
Step 4Â Â Configure DHCP relay agent IP address to use VRRP virtual IP.
admin@Switch2# set protocols dhcp relay interface vlan10 relay-agent-address 11.251.201.3
Other Configuration
Step1Â Â Â Â Â Â Â Configure VLAN and VLAN interface.
admin@Switch2# set vlans vlan-id 30 admin@Switch2# set vlans vlan-id 30 l3-interface vlan30 admin@Switch2# set interface gigabit-ethernet te-1/1/42 family ethernet-switching native-vlan-id 30 admin@Switch2# set l3-interface vlan-interface vlan30 address 20.1.1.1 prefix-length 24
Step2       Configure a route to DHCP server. The following command uses the static route as an example.   Â
admin@Switch2# set protocols static route 192.168.2.0/24 next-hop 20.1.1.2
Step3       Commit the configuration.   Â
admin@Switch2# commit
Switch3
Step1       Enable aggregation interface with LACP mode.      Â
admin@Switch3# set interface aggregate-ethernet ae1 aggregated-ether-options lacp enable true
Step2         Add member interfaces to a LAG.     Â
admin@Switch3# set interface gigabit-ethernet ge-1/1/1 ether-options 802.3ad ae1 admin@Switch3# set interface gigabit-ethernet ge-1/1/2 ether-options 802.3ad ae1
Step3         Configure VLAN.      Â
admin@Switch3# set vlans vlan-id 10 admin@Switch3# set interface aggregate-ethernet ae1 family ethernet-switching native-vlan-id 10
Step4         Commit the configuration. Â
admin@Switch3# commit
Verify the Configuration
- You can use the run show mlag domain command to display the global MLAG domain information.
admin@Switch1# run show mlag domain summary Domain ID: 10   Domain MAC: 62:9E:73:FF:00:01   Node ID: 0 ----------------------------------------------------------------------- Peer Link Peer IP  Peer Vlan Neighbor Status Config Matched MAC Synced # of Links --------- --------------- --------- --------------- -------------- ----------  ---------- ae48    10.10.10.2  4088    ESTABLISHED Yes  Yes         1
- You can use the run show mlag link command to display MLAG link information.
admin@Switch1# run show mlag link summary # of Links: 1 Link  Local LAG  Link Status  Local Status  Peer Status  Config Matched  Flood ----  ---------  -----------  ------------  -----------  --------------  ----- 1     ae71        IDLE         UP            UNKNOWN      No              No
- You can use the run show mlag consistency-parameter command to display the result of MLAG configuration consistency check, including the global and per MLAG configuration.
admin@Switch1# run show mlag consistency-parameter link 1 Port Configurations: ----------------------------------------------------------------- Property          Local Value     Peer Value      Result ----------------------- --------------- --------------- ------ MTU                     1514            1514            PASS Mac Learning            Yes             Yes             PASS Lag Mode                LACP            LACP            PASS Native Vlan             1               1              PASS Port Vlan Mode          Trunk          Trunk          PASS Spanning-Tree Configurations: ----------------------------------------------------------------- Property                Local Value     Peer Value      Result ----------------------- --------------- --------------- ------ Mode                                                 PASS admin@Switch1# run show mlag consistency-parameter summary Overall : PASS -------------- Global : PASS Link 1 : PASS MLAG Configurations: ----------------------------------------------------------------- Property                Local Value     Peer Value      Result ----------------------- --------------- --------------- ------ Domain ID               1               1               PASS Node ID                 0               1               PASS Peer VLAN               4088            4088            PASS Link Count              1               1              PASS Link IDs                2               2       PASS                          Spanning-Tree Configurations: ----------------------------------------------------------------- Property                Local Value     Peer Value      Result ----------------------- --------------- --------------- ------ Enable                  No              No              PASS   DHCP Snooping Configurations: ----------------------------------------------------------------- Property                Local Value     Peer Value      Result ----------------------- --------------- --------------- ------ Enable                  No              No              PASS IGMP Snooping Configurations: ----------------------------------------------------------------- Property                Local Value     Peer Value      Result ----------------------- --------------- --------------- ------ Enable                  No              No              PASS
- You can use run show vrrp command to view the configuration information of VRRP group. The result of show command on Switch1 is as follows.
admin@Switch1# run show vrrp Interface: vlan10 VRID: 100 Version: 2 Load-balance: enable State: Master Master IP: 11.251.201.1 Virtual MAC: 00:00:5e:00:01:01 Preempt: disable Adver Interval: 1 Priority: 250 Virtual IP: 11.251.201.3 Auth-type: none Auth-key:
- DHCP client can obtain the IP address normally.
Copyright © 2024 Pica8 Inc. All Rights Reserved.