Fallback

This scenario shows how to configure an Ethernet interface with DHCP and with a fallback IP address.

Test DHCP client

Description

Initially, DHCP-Server (DUT1) is disabled. Since no IP address is received on the client-side (DUT0), the fallback IP address is used instead. Once DHCP-Server is enabled, DUT0 starts using the new IP address.

Scenario

Step 1: Set the following configuration in DUT1:

set interfaces ethernet eth0 address 192.168.100.1/24
set interfaces ethernet eth1 address 10.0.0.1/24
set service dhcp-server shared-network dhcpserver subnet 192.168.100.0/24 options default-router 192.168.100.1
set service dhcp-server shared-network dhcpserver subnet 192.168.100.0/24 start 192.168.100.50 stop 192.168.100.50
set service dhcp-server disable

Step 2: Set the following configuration in DUT0:

set interfaces ethernet eth0 address dhcp
set interfaces ethernet eth0 dhcp client fallback 192.168.100.100/24

Step 3: Run command interfaces ethernet show at DUT0 and check if output contains the following tokens:

192.168.100.100/24

Show output

-----------------------------------------------------------------
Name           IP Address           Admin  Oper  Vrf  Description
-----------------------------------------------------------------
eth0  192.168.100.100/24            up     up
      fe80::dcad:beff:feef:6c10/64
eth1                                down   down

Step 4: Ping IP address 192.168.100.1 from DUT0:

admin@DUT0$ ping 192.168.100.1 count 1 size 56 timeout 1

Show output

PING 192.168.100.1 (192.168.100.1) 56(84) bytes of data.
64 bytes from 192.168.100.1: icmp_seq=1 ttl=64 time=0.607 ms

--- 192.168.100.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.607/0.607/0.607/0.000 ms

Step 5: Set the following configuration in DUT1:

del service dhcp-server disable

Step 6: Run command service dhcp-client renew interface eth0 at DUT0 and expect this output:

Show output

Renewing DHCP lease on interface eth0...

Step 7: Run command interfaces ethernet show at DUT0 and check if output contains the following tokens:

192.168.100.50/24

Show output

-----------------------------------------------------------------
Name           IP Address           Admin  Oper  Vrf  Description
-----------------------------------------------------------------
eth0  192.168.100.50/24             up     up
      fe80::dcad:beff:feef:6c10/64
eth1                                down   down

Step 8: Ping IP address 192.168.100.1 from DUT0:

admin@DUT0$ ping 192.168.100.1 count 1 size 56 timeout 1

Show output

PING 192.168.100.1 (192.168.100.1) 56(84) bytes of data.
64 bytes from 192.168.100.1: icmp_seq=1 ttl=64 time=0.338 ms

--- 192.168.100.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.338/0.338/0.338/0.000 ms

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