Wired Networks

Multiple IP addresses per VLAN and loopback interface

Aruba Employee

Introduction- ArubaOS supports multiple IP addresses per VLAN and loopback interface. This allows the user to specify any number of secondary IP addresses. Secondary IP address can be used in a variety of situations, such as the
following: 

  • If an insufficient number of host addresses are available on a particular network segment. Using secondary IP addresses on the routers or access devices allows you to have two logical subnets using one physical subnet
  • If the an older network is built using Layer 2 bridges and has no subnetting. Secondary addresses can aid in the transition to a subnetted, router-based network.
  • Two subnets of a single network might be otherwise separated by another network. You can create a single network from subnets that are physically separated by another network using a secondary address.

Feature Notes- Important Points to Remember:

  • OSPF advertises the secondary IP address in the router LSA but it does not form adjacency on the secondary IP address. 
  • PIM will not send hello packets on the secondary IP address. 
  • DHCP servers identify the subnets associated with secondary IP addresses used for allocation.

Configuration Steps- Configuring Secondary IP:

To configure a secondary IP address, use the following command:

(host) (vlan "1") #ip address 1.1.1.1 255.255.255.0 ?
secondary Make this IP address a secondary address


Sample Configuration:

(host) (config) #interface vlan 2
(host) (vlan "2") #ip address 1.1.1.1 255.255.255.0 secondary

Answer- (host) (vlan "2") #show interface vlan 2
VLAN2 is administratively Up, Line protocol is Up
Hardware is CPU Interface, Address is 00:0b:86:6a:1c:c0
Description: 802.1Q VLAN
Internet address is 20.20.20.1, Netmask is 255.255.255.0
Internet address is 1.1.1.1, Netmask is 255.255.255.0 secondary
IPV6 link-local address is fe80::b:8600:26a:1cc0
Global Unicast address(es):
Routing interface is enable, Forwarding mode is enable
Directed broadcast is disabled, BCMC Optimization disabled

Verification- (ArubaS1500-24P) (config) #interface vlan  20
(ArubaS1500-24P) (vlan "20") #ip address  10.1.1.4 255.255.255.0 secondary
(ArubaS1500-24P) (vlan "20") #show ip interface brief

Flags: S - Secondary IP address
Probe: U - Up, D - Down, U/O - Up & Own IP, N/A - Not Applicable
Interface                   IP Address / IP Netmask        Admin   Protocol Probe  Flags
vlan 1                   10.17.169.165 / 255.255.255.0     Up      Up       N/A
vlan 10                     unassigned / unassigned        Up      Down     N/A
vlan 20                       20.1.1.2 / 255.255.255.0     Up      Up       N/A
vlan 20                       10.1.1.4 / 255.255.255.0     Up      Up       N/A    S --> S Flag indicate its secondary
gre-tunnel 1                unassigned / unassigned        Up      Down     N/A

 

Internal Note- Verified and tested in 7.4.0.2 image version.

Version history
Revision #:
1 of 1
Last update:
‎04-05-2015 11:18 PM
Updated by:
 
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