Description

This article explains a limitation of EX Series devices, in which a secondary TFTP server cannot be configured in the same DHCP pool.

Symptoms

Example:

Configure a primary TFTP server with IP 10.32.201.20.  

{master:0}
labroot@lab001> edit
Entering configuration mode
 
{master:0}[edit]
labroot@lab001# load set terminal
[Type ^D at a new line to end input]
set system services dhcp-local-server group VOICE-US_POOL interface irb.688
set access address-assignment pool VOICE-US_POOL family inet network 10.189.70.0/24
set access address-assignment pool VOICE-US_POOL family inet range IP_RANGE low 10.189.70.10
set access address-assignment pool VOICE-US_POOL family inet range IP_RANGE high 10.189.70.254
set access address-assignment pool VOICE-US_POOL family inet dhcp-attributes router 10.189.70.4
set access address-assignment pool VOICE-US_POOL family inet dhcp-attributes option 150 ip-address 10.32.201.20
load complete
 
{master:0}[edit]
labroot@lab001# commit
[edit protocols]
  'bgp'
    warning: requires 'bgp' license
configuration check succeeds
commit complete
 
{master:0}[edit]
labroot@lab001# show | display set |match VOICE-US_POOL
set system services dhcp-local-server group VOICE-US_POOL interface irb.688
set access address-assignment pool VOICE-US_POOL family inet network 10.189.70.0/24
set access address-assignment pool VOICE-US_POOL family inet range IP_RANGE low 10.189.70.10
set access address-assignment pool VOICE-US_POOL family inet range IP_RANGE high 10.189.70.254
set access address-assignment pool VOICE-US_POOL family inet dhcp-attributes router 10.189.70.4
set access address-assignment pool VOICE-US_POOL family inet dhcp-attributes option 150 ip-address 10.32.201.20

Now, add the secondary TFTP server with the IP (10.32.201.30) to the existing pool and commit.  The commit will be successful. However, primary server IP will be replaced by the secondary one (10.32.201.30): 

{master:0}[edit]
labroot@lab001# set access address-assignment pool VOICE-US_POOL family inet dhcp-attributes option 150 ip-address 10.32.201.30
 
{master:0}[edit]
labroot@lab001# commit
[edit protocols]
  'bgp'
    warning: requires 'bgp' license
configuration check succeeds
commit complete

Once the commit is successful, the primary server IP is replaced by the secondary IP. The following output shows the behavior. 

{master:0}[edit]
labroot@lab001# show | display set |match VOICE-US_POOL
set system services dhcp-local-server group VOICE-US_POOL interface irb.688
set access address-assignment pool VOICE-US_POOL family inet network 10.189.70.0/24
set access address-assignment pool VOICE-US_POOL family inet range IP_RANGE low 10.189.70.10
set access address-assignment pool VOICE-US_POOL family inet range IP_RANGE high 10.189.70.254
set access address-assignment pool VOICE-US_POOL family inet dhcp-attributes router 10.189.70.4
set access address-assignment pool VOICE-US_POOL family inet dhcp-attributes option 150 ip-address 10.32.201.30

Solution

This is a hardware limitation in EX Series platforms.