Scenario 3: Using Proxy Arp To Enable An Ons 15454 Gateway; Figure 19-2 Scenario 2: Ctc And Ons 15454S Connected To Router (Ansi And Etsi) - Cisco ONS 15454 DWDM Installation And Operation Manual

19.2.3 Scenario 3: Using Proxy ARP to Enable an ONS 15454 Gateway

Figure 19-2 Scenario 2: CTC and ONS 15454s Connected to Router (ANSI and ETSI)

Subnet Mask 255.255.255.0
Default Router = 192.168.2.1
19.2.3 Scenario 3: Using Proxy ARP to Enable an ONS 15454 Gateway
ARP matches higher-level IP addresses to the physical addresses of the destination host. It uses a lookup
table (called ARP cache) to perform the translation. When the address is not found in the ARP cache, a
broadcast is sent out on the network with a special format called the ARP request. If one of the machines
on the network recognizes its own IP address in the request, it sends an ARP reply back to the requesting
host. The reply contains the physical hardware address of the receiving host. The requesting host stores
this address in its ARP cache so that all subsequent datagrams (packets) to this destination IP address
can be translated to a physical address.
Proxy ARP enables one LAN-connected ONS 15454 to respond to the ARP request for ONS 15454s not
connected to the LAN. (ONS 15454 proxy ARP requires no user configuration.) For this to occur, the
DCC-connected ONS 15454s must reside on the same subnet as the LAN-connected (gateway)
ONS 15454. When a LAN device sends an ARP request to an ONS 15454 that is not connected to the
LAN, the gateway ONS 15454 (the one connected to the LAN) returns its MAC address to the LAN
device. The LAN device then sends the datagram for the remote ONS 15454 to the MAC address of the
proxy ONS 15454. The proxy ONS 15454 uses its routing table to forward the datagram to the non-LAN
ONS 15454.
Cisco ONS 15454 DWDM Installation and Operations Guide, R4.7
19-4
LAN A
CTC Workstation
IP Address 192.168.1.100
Subnet Mask 255.255.255.0
Default Gateway = 192.168.1.1
Host Routes = N/A
ONS 15454 #1
IP Address 192.168.2.10
Static Routes = N/A
Int "A"
Int "B" Router
IP Address of interface "A" to LAN "A" 192.168.1.1
IP Address of interface "B" to LAN "B" 192.168.2.1
Subnet Mask 255.255.255.0
Default Router = N/A
Host Routes = N/A
ONS 15454 #2
IP Address 192.168.2.20
Subnet Mask 255.255.255.0
Default Router = 192.168.2.1
Static Routes = N/A
Ring
Chapter 19 CTC Connectivity Reference
LAN B
ONS 15454 #3
IP Address 192.168.2.30
Subnet Mask 255.255.255.0
Default Router = 192.168.2.1
Static Routes = N/A
September 2004