Foundry Networks Switch and Router Installation And Configuration Manual page 962

Foundry Switch and Router Installation and Configuration Guide
NOTE: If the Foundry device's ARP table does not contain the requested host, the Foundry device forwards
the ARP request on Layer 2 to the same VLAN as the one that received the ARP request. Then the device
sends an ARP for the destination to the other VLANs that are using the same IP sub-net address.
• If the destination is in the same VLAN as the source, the Foundry device does not need to perform a proxy
ARP.
To configure multiple VLANs to use the same IP sub-net address:
• Configure each VLAN, including adding tagged or untagged ports.
• Configure a separate virtual interface for each VLAN, but do not add an IP sub-net address to more than one
of the virtual interfaces.
• Configure the virtual interfaces that do not have the IP sub-net address to "follow" the virtual interface that
does have the address.
USING THE CLI
To configure the VLANs shown in Figure 25.18, you could enter the following commands.
BigIron(config)# vlan 1 by port
BigIron(config-vlan-1)# untag ethernet 1/1
BigIron(config-vlan-1)# tag ethernet 1/8
BigIron(config-vlan-1)# router-interface ve 1
Syntax: ip follow ve <num>
The commands above configure port-based VLAN 1. The VLAN has one untagged port (1/1) and a tagged port
(1/8). In this example, all three VLANs contain port 1/8 so the port must be tagged to allow the port to be in
multiple VLANs. You can configure VLANs to share a Layer 3 protocol interface regardless of tagging. A
combination of tagged and untagged ports is shown in this example to demonstrate that sharing the interface does
not change other VLAN features.
Notice that each VLAN still requires a unique virtual interface.
The following commands configure port-based VLANs 2 and 3.
BigIron(config-vlan-1)# vlan 2 by port
BigIron(config-vlan-2)# untag ethernet 1/2
BigIron(config-vlan-2)# tag ethernet 1/8
BigIron(config-vlan-2)# router-interface ve 2
BigIron(config-vlan-2)# vlan 3 by port
BigIron(config-vlan-3)# untag ethernet 1/5 to 1/6
BigIron(config-vlan-3)# tag ethernet 1/8
BigIron(config-vlan-3)# router-interface ve 3
The following commands configure an IP sub-net address on virtual interface 1.
BigIron(config-vlan-3)# interface ve 1
BigIron(config-vif-1)# ip address 10.0.0.1/24
The following commands configure virtual interfaces 2 and 3 to "follow" the IP sub-net address configured on
virtual interface 1.
BigIron(config-vif-1)# interface ve 2
BigIron(config-vif-2)# ip follow ve 1
BigIron(config-vif-2)# interface ve 3
BigIron(config-vif-3)# ip follow ve 1
NOTE: Since virtual interfaces 2 and 3 do not have their own IP sub-net addresses but instead are "following"
virtual interface a's IP address, you still can configure an IPX or AppleTalk interface on virtual interfaces 2 and 3.
25 - 42 December 2000