Fix:
Avaya VOIP phones can get DHCP options from the DHCP servers.
Create a vendor class DHCP option (if the user is planning to create a vendor class the name they specify in the Name field is case sensitive, please check with the Vendor's document and use the suggested name by the vendor otherwise the phone will ignore the DHCP Options) or a standard DHCP option (not case sensitive).
For Option 150 use type as "Byte Array" and for Option 176 use type as "Text Array"
Go to the DHCP range and choose the option they have created and specify the values.
Example: option 176 MCIPADD=10.69.96.250,MCPORT=1719,TFTPSRVR=10.69.121.251
option 150 10.69.171.251 10.69.121.251
