Restrict DHCPD to only respond to arista devices

[jerearista]

Add a filter to DHCPD.conf so it only responds to Arista devices by default.

  option broadcast-address 192.1.1.255;
  option subnet-mask 255.255.255.0;

  class "arista" {
    match if substring(option vendor-class-identifier, 0, 6) = "Arista"
    option bootfile-name "http://10.10.10.11:8080/bootstrap";
  }

  pool {
    #range 192.1.1.6;
    allow members of "arista";
  }

}