![background image](http://html.mh-extra.com/html/foundry-networks/switch-and-router/switch-and-router_installation-and-configuration-manual_2324275961.webp)
Configuring Virtual LANs (VLANs)
December 2000
25 - 41
Figure 25.18
Multiple port-based VLANs with the same protocol address
Each VLAN still requires a separate virtual interface. However, all three VLANs now use the same IP sub-net
address.
In addition to conserving IP sub-net addresses, this feature allows containment of Layer 2 broadcasts to segments
within an IP sub-net. For ISP environments where the same IP sub-net is allocated to different customers, placing
each customer in a separate VLAN allows all customers to share the IP sub-net address, while at the same time
isolating them from one another’s Layer 2 broadcasts.
NOTE:
You can provide redundancy to an IP sub-net address that contains multiple VLANs using a pair of
Foundry Layer 3 Switches configured for Foundry’s VRRP (Virtual Router Redundancy Protocol) or FSRP
(Foundry Standby Router Protocol).
The Foundry device performs proxy Address Resolution Protocol (ARP) for hosts that want to send IP traffic to
hosts in other VLANs that are sharing the same IP sub-net address. If the source and destination hosts are in the
same VLAN, the Foundry device does not need to use ARP.
•
If a host attached to one VLAN sends an ARP message for the MAC address of a host in one of the other
VLANs using the same IP sub-net address, the Foundry device performs a proxy ARP on behalf of the other
host. The Foundry device then replies to the ARP by sending the virtual interface MAC address. The
Foundry device uses the same MAC address for all virtual interfaces.
When the host that sent the ARP then sends a unicast packet addressed to the virtual interface’s MAC
address, the device switches the packet on Layer 3 to the destination host on the VLAN.
BigIron
Switching Router
VLAN 2
VE 1
-IP 10.0.0.1/24
VLAN 4
VE 3
-Follow VE 1
VLAN 2
VLAN 3
VLAN 4
VLAN 3
VE 2
-Follow VE 1
Summary of Contents for Switch and Router
Page 2: ...December 2000 Copyright 2000 by Foundry Networks Inc ...
Page 26: ...Foundry Switch and Router Installation and Configuration Guide xxvi December 2000 ...
Page 64: ...Foundry Switch and Router Installation and Configuration Guide 2 34 December 2000 ...
Page 162: ...Foundry Switch and Router Installation and Configuration Guide 5 38 December 2000 ...
Page 196: ...Foundry Switch and Router Installation and Configuration Guide 6 34 December 2000 ...
Page 208: ...Foundry Switch and Router Installation and Configuration Guide 7 12 December 2000 ...
Page 236: ...Foundry Switch and Router Installation and Configuration Guide 8 28 December 2000 ...
Page 258: ...Foundry Switch and Router Installation and Configuration Guide 9 22 December 2000 ...
Page 420: ...Foundry Switch and Router Installation and Configuration Guide 13 32 December 2000 ...
Page 442: ...Foundry Switch and Router Installation and Configuration Guide 14 22 December 2000 ...
Page 554: ...Foundry Switch and Router Installation and Configuration Guide 15 112 December 2000 ...
Page 574: ...Foundry Switch and Router Installation and Configuration Guide 16 20 December 2000 ...
Page 626: ...Foundry Switch and Router Installation and Configuration Guide 17 52 December 2000 ...
Page 682: ...Foundry Switch and Router Installation and Configuration Guide 18 56 December 2000 ...
Page 826: ...Foundry Switch and Router Installation and Configuration Guide 20 20 December 2000 ...
Page 994: ...Foundry Switch and Router Installation and Configuration Guide 26 10 December 2000 ...
Page 1004: ...Foundry Switch and Router Installation and Configuration Guide B 6 December 2000 ...
Page 1044: ...Foundry Switch and Router Installation and Configuration Guide C 40 December 2000 ...
Page 1048: ...Foundry Switch and Router Installation and Configuration Guide D 4 December 2000 ...
Page 1070: ...Foundry Switch and Router Installation and Configuration Guide Index 18 December 2000 ...