Edit 2:
As you mentioned...
ip route 10.1.0.0 255.255.0.0 iface0
Forces the Brocade to proxy-arp for every destination in 10.1.0.0/16 as if it was directly connected to iface0.
I can't respond about Brocade's ARP cache implementation, but I would simply point out the easy solution to your problem... configure your route differently:
ip route 10.1.0.0 255.255.0.0 CiscoNextHopIP
By doing this, you prevent the Brocade from ARP-ing for all of 10.1.0.0/16 (note, you might need to renumber the link between R1 and R2 to be outside 10.1.0.0/16, depending on Brocade's implementation of things).
Original answer:
I expect that in most, or even all, implementations, there is a hard limit on the capacity of the ARP table.
Cisco IOS CPU routers are only limited by the amount of DRAM in the router, but that is typically not going to be a limiting factor. Some switches (like Catalyst 6500) have a hard limitation on the adjacency table (which is correlated to the ARP table); Sup2T has 1 Million adjacencies.
So, what happens when the ARP cache is full and a packet is offered with a destination (or next-hop) that isn't cached?
Cisco IOS CPU routers don't run out of space in the ARP table, because those ARPs are stored in DRAM. Let's assume you're talking about Sup2T. Think of it like this, suppose you had a Cat6500 + Sup2T and you configured all Vlans possible, technically that is
4094 total Vlans - Vlan1002 - Vlan1003 - Vlan1004 - Vlan1005 = 4090 Vlans
Assume you make each Vlan a /24 (so that's 252 possible ARPs), and you pack every Vlan full... that is 1 Million ARP entries.
4094 * 252 = 1,030,680 ARP Entries
Every one of those ARPs would consume a certain amount of memory in the ARP table itself, plus the IOS adjacency table. I dont know what it is, but let's say the total ARP overhead is 10 Bytes...
That means you have now consumed 10MB for ARP overhead; it still isn't very much space... if you were that low on memory, you would see something like %SYS-2-MALLOCFAIL.
With that many ARPs and a four hour ARP timeout, you would have to service almost 70 ARPs per second on average; it's more likely that the maintenance on 1 million ARP entries would drain the CPU of the router (potentially CPUHOG messages).
At this point, you could start bouncing routing protocol adjacencies and have IPs that are just unreachable because the router CPU was too busy to ARP for the IP.
I want to coonect those 2 lan's with a router , Is that possible ?
Yes, that is what routers do! If you already have gateway IPs configured then that implies that you already have at least one router (or device acting as a router) configured.
If these are actual LAN subnets then you ideally want to route all traffic through the gateways you already have configured.
A much less optimal solution would be to configure your gateway device(s) to send ICMP redirects instructing the hosts to route traffic through a different gateway IP (i.e. your new router) when trying to get to one of those subnets.
what are the modifications to do to my configurations
With no configs posted here, it's hard to say!
Best Answer
ARP requests are broadcast, and broadcasts are bounded by layer-3 devices, such as routers. Frames are layer-2 PDUs, and are also bounded by routers. Routers will strip off the layer-2 frame header before forwarding the layer-3 packet, which is the payload of the layer-2 frame. Hence, layer-2 frame addresses are only relevant or seen in the layer-2 LAN.
MAC addresses are the layer-2 frame addresses of some layer-2 LAN protocols (IEEE LAN protocols, such as ethernet, Wi-Fi, token ring, etc.). Some layer-2 protocols use 48-bit MAC addresses, some use 64-bit MAC addresses, some use something else, and some use nothing at all for addressing.
Layer-3 addresses, such as IPv4 or IPv6 addresses, are used to move layer-3 packets between different layer-3 networks. In almost all cases, each layer-2 LAN will use a different layer-3 network. There are corner cases where this may not be true, but they are special and have nothing to do with what you are studying.
Layer-2 addresses are used to deliver directly from one host to another host on the layer-2 LAN. ARP (Address Resolution Protocol) is used to resolve a layer-2 address from a layer-3 address so that the packet can be encapsulated in a layer-2 frame. For hosts on the same layer-2 LAN, there will be a one-to-one correspondence between the layer-3 address and the layer-2 address. If the destination layer-3 address is on a different layer-3 network, the host will use ARP to get the layer-2 address of its configured gateway (the host that knows how to reach other networks, usually a router), and the layer-3 packet is encapsulated in a layer-2 frame with the layer-2 address of the gateway, even though the layer-3 address is for a different host on a different network.
The gateway will strip off the layer-2 frame, inspect the layer-3 destination address, make a decision on which interface to forward the layer-3 packet, and create a new layer-2 frame for the packet on the new interface.