route-4-dhcp

Calculate Classless Route Option 121, RFC 3442, The Classless Static Route Option for Dynamic Host Configuration Protocol (DHCP) version 4

Classless Route Option Format

The code for this option is 121, and its minimum length is 5 bytes. This option can contain one or more static routes, each of which consists of a destination descriptor and the IP address of the router that should be used to reach that destination.

 Code  Len Destination 1   Router 1
+-----+---+----+-----+----+----+----+----+----+
| 121 | n | d1 | ... | dN | r1 | r2 | r3 | r4 |
+-----+---+----+-----+----+----+----+----+----+

 Destination 2        Router 2
+----+-----+----+----+----+----+----+
| d1 | ... | dN | r1 | r2 | r3 | r4 |
+----+-----+----+----+----+----+----+

Sample use

$ rfc3442.route-4-dhcp.pl 10.0.0.0/8 192.168.88.2 172.16.0.0/12 192.168.88.2 192.168.0.0/16 192.168.88.2 0.0.0.0/0 192.168.88.1
option_121_route_10.0.0.0/8_via_192.168.88.2 : 0x080ac0a85802
option_249_route_10.0.0.0/8_via_192.168.88.2 : 0x080ac0a85802
option_121_route_172.16.0.0/12_via_192.168.88.2 : 0x0cac10c0a85802
option_249_route_172.16.0.0/12_via_192.168.88.2 : 0x0cac10c0a85802
option_121_route_192.168.0.0/16_via_192.168.88.2 : 0x10c0a8c0a85802
option_249_route_192.168.0.0/16_via_192.168.88.2 : 0x10c0a8c0a85802
option_121_route_0.0.0.0/0_via_192.168.88.1 : 0x00c0a85801
option_249_route_0.0.0.0/0_via_192.168.88.1 : 0x00c0a85801
aggregate_opt_121 : 0x080ac0a858020cac10c0a8580210c0a8c0a8580200c0a85801
aggregate_opt_249 : 0x080ac0a858020cac10c0a8580210c0a8c0a8580200c0a85801

Sample use (Powershell)

PS C:\Tools\route-4-dhcp> .\Calculate-Route-Option-121.ps1  10.0.0.0/8, 192.168.88.2, 172.16.0.0/12, 192.168.88.2, 192.168.0.0/16, 192.168.88.2, 0.0.0.0/0, 192.168.88.1
Option 121 route 10.0.0.0/8 via 192.168.88.2 : 0x080ac0a85802
Option 121 route 172.16.0.0/12 via 192.168.88.2 : 0x0cac10c0a85802
Option 121 route 192.168.0.0/16 via 192.168.88.2 : 0x10c0a8c0a85802
Option 121 route 0.0.0.0/0 via 192.168.88.1 : 0x00c0a85801
Aggregate option 121 : 0x080ac0a858020cac10c0a8580210c0a8c0a858020000c0a85801

See more http://oldengremlin.blogspot.com/2016/10/routeros-dhcp.html