Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 85)

Brocade ICX 6650 Layer 3 Routing Configuration Guide 67
53-1002603-01
Configuring IP parameters – Layer 3 Switches
Changing the maximum number of hops to a BootP relay server
Each BootP or DHCP request includes a field Hop Count field. The Hop Count field indicates how
many routers the request has passed through. When the Layer 3 Switch receives a BootP/DHCP
request, the Layer 3 Switch looks at the value in the Hop Count field:
• If the hop count value is equal to or less than the maximum hop count the Layer 3 Switch
allows, the Layer 3 Switch increments the hop count by one and forwards the request.
• If the hop count is greater than the maximum hop count the Layer 3 Switch allows, the Layer 3
Switch discards the request.
To change the maximum number of hops the Layer 3 Switch allows for forwarded BootP/DHCP
requests, use either of the following methods.
NOTE
The BootP and DHCP hop count is not the TTL parameter.
To modify the maximum number of BootP/DHCP hops, enter the following command.
Brocade(config)#bootp-relay-max-hops 10
This command allows the Layer 3 Switch to forward BootP/DHCP requests that have passed
through ten previous hops before reaching the Layer 3 Switch. Requests that have traversed 11
hops before reaching the switch are dropped. Since the hop count value initializes at zero, the hop
count value of an ingressing DHCP Request packet is the number of Layer 3 routers that the packet
has already traversed.
Syntax: bootp-relay-max-hops 1 through 15
DHCP Server
All Brocade ICX 6650 devices can be configured to function as DHCP Servers.
Dynamic Host Configuration Protocol (DHCP) is a computer networking protocol used by devices
(DHCP clients) to obtain leased (or permanent) IP addresses. DHCP is an extension of the
Bootstrap Protocol (BOOTP). The differences between DHCP and BOOTP are the address allocation
and renewal process.
DHCP introduces the concept of a lease on an IP address. Refer to “How DHCP Client-Based
Auto-Configuration and flash image update works” on page 82. The DHCP server can allocate an IP
address for a specified amount of time, or can extend a lease for an indefinite amount of time.
DHCP provides greater control of address distribution within a subnet. This feature is crucial if the
subnet has more devices than available IP address. In contrast to BOOTP, which has two types of
messages that can be used for leased negotiation, DHCP provides 7 types of messages. Refer to
“Supported options for DHCP Servers” on page 85.
DHCP allocates temporary or permanent network IP addresses to clients. When a client requests
the use of an address for a time interval, the DHCP server guarantees not to reallocate that
address within the requested time and tries to return the same network address each time the
client makes a request. The period of time for which a network address is allocated to a client is
called a lease. The client may extend the lease through subsequent requests. When the client is
done with the address, they can release the address back to the server. By asking for an indefinite
lease, clients may receive a permanent assignment.