ARP and Proxy Arp:
- method to learn another hosts MAC address
- all 0’s in des MAC
- ARP protocol type: 0x0806
- Proxy Arp: if a router can route packet to the target host in another subnet, router uses proxy ARP on behalf of the target.
RARP, BOOTP and DHCP
- main function: how host can discover it’s own IP address plus other details
- RARP: same old ARP message but uses it’s own MAC address as TARGET and IP address of 0.0.0.0. RARP server must be on the same subnet as the client.
- BOOTP: commands are encapsulated in an IP and UDP header. Router can forward the BOOTP packets to other subnets. Also allows assignment of: subnet mask, default gateway, DNS address and IP address of a boot server. STILL REQUIRES CONFIGURATION LIKE RARP.
- DHCP: Router would change the clients DHCP request from a source and destination of 255.255.255.255 to a source of directed broadcast of clients subnet (e.g 10.1.1.255) and destination of DHCP server. DHCP response would be forwarded to destination 10.1.1.255.
- Only configuration command: ip helper-address <dhcpserverIP> on the inside router interface (client side).
- DHCP pool includes keys such as: subnet, default gateway, length of lease time, dns domain name.
- you can use (global) ip dhcp excluded-address command to exclude IP hosts. (global configuration)