09-22-2009 06:20 AM - edited 03-06-2019 07:50 AM
Hi,
In our network we are using an interface with the IP like below
interface GigabitEthernet0/1
ip address 192.168.191.10 255.255.255.0 secondary
ip address XX.XXX.1.2 255.255.255.0
duplex auto
speed auto
media-type rj45
no negotiation auto
standby 10 ip XX.XXX.1.1
standby 10 ip 192.168.191.1 secondary
Now we need some requirement to spilit up the subnet XX.XXX.1.0/24 into subneting
like adding one more subnet XX.XXX.1.32/27 in the same ineterface
can i do the same like this
interface GigabitEthernet0/1
ip address XX.XXX.1.61 255.255.255.224 secondary
ip address 192.168.191.10 255.255.255.0 secondary
ip address XX.XXX.1.2 255.255.255.0
duplex auto
speed auto
media-type rj45
no negotiation auto
standby 10 ip XX.XXX.1.1
standby 10 ip 192.168.191.1 secondary
standby 10 ip XX.XXX.1.33 secondary
will it make any issue since we are using the same subnet as /24 and als0 /27
can any suggest me
09-22-2009 07:08 AM
Hi,vinoth.kumar
ip add 12.12.12.32 255.255.255.224 secondary
ip add 12.12.12.31 255.255.255.224 secondary
will not work under the interface, they are the network bit and broadcast bit for the first two /27 subnet.
hope it help
Yang
09-22-2009 07:17 AM
Thanks for the reply
what i need is in the inter gi o/1 we are using 10.5.1.0 /24
can i use the same interface for the subnet 10.5.1.32/27
i guess both the subnet as the different net id and broadcast id
ilke this
interface GigabitEthernet0/1
ip address 192.168.191.10 255.255.255.0 secondary
ip address 10.5.1.33 255.255.255.224 secondary
ip address 10.5.1.1 255.255.255.0
duplex auto
speed auto
media-type rj45
no negotiation auto
09-22-2009 07:30 AM
Hi,
currently you have 10.5.1.1 255.255.255.0, which is full class C range.
if you want to furter subnet this range to make smaller ranges then you will need to adjust the subnet mask on the current range and then add further secondry range.
your new subnets will become 10.5.1.0/27 and 10.5.1.32/27
this means your interface configuration will become af follows:-
interface GigabitEthernet0/1
ip address 192.168.191.10 255.255.255.0 secondary
ip address 10.5.1.33 255.255.255.224 secondary
ip address 10.5.1.1 255.255.255.224
duplex auto
speed auto
media-type rj45
no negotiation auto
Remember to adjust all other devices/DHCP scopes etc. with the new subnet mask and correct default gateway otherwise you will have problems.
Hope this helps.....
Shaheen
09-22-2009 07:39 AM
sorry i am not going to do any modification on the existing interface IP configuration
Existing is :
interface GigabitEthernet0/1
ip address 192.168.191.10 255.255.255.0 secondary
ip address 10.5.1.1 255.255.255.0
duplex auto
speed auto
media-type rj45
no negotiation auto
in the existing config i used 10.5.1.1 255.255.255.0 which is /24 prefix
Now we need to use the seperate ssubnetting for some reason
that is 10.5.1.32/255.255.255.224 which as the host range of 33-62 which is coming under the existing interface range
new what i am going to do
interface GigabitEthernet0/1
ip address 192.168.191.10 255.255.255.0 secondary
ip address 10.5.1.33 255.255.255.224 secondary
ip address 10.5.1.1 255.255.255.0
duplex auto
speed auto
media-type rj45
no negotiation auto
Will it work
09-22-2009 07:46 AM
no, it will not work as host range 33-62 falls in with your existing subnet 10.5.1.1/24 (which has a host range 10.5.1.1 to 10.5.1.254)
this link will help you to explain how/why to subnet
http://articles.techrepublic.com.com/5100-10878_11-5033672.html
Hope this helps...please rate all helpfull posts
Shaheen
09-22-2009 08:07 AM
Thanks for your information
Sorry to raise the question again
In logic if we enable a secondary Ip on the same interfcae it will act as the Logical interface
for example routing between the interface so if i assign the subneted ip range on to the interface it will work
and also i tried configuring like this and no error as came
Cat-6500# conf t
Enter configuration commands, one per line. End with CNTL/Z.
Cat-6500(config)#interface GigabitEthernet3/30
Cat-6500(config-if)#ip address 10.5.1.1 255.255.255.0
Cat-6500(config-if)#ip address 10.5.1.33 255.255.255.224 se
Cat-6500(config-if)#ip address 10.5.1.33 255.255.255.224 secondary
ICMP redirect is disabled on interfaces with secondary IP address
Cat-6500#sh run int gi 3/30
Building configuration...
Current configuration : 151 bytes
!
interface GigabitEthernet3/30
ip address 10.5.1.33 255.255.255.224 secondary
ip address 10.5.1.1 255.255.255.0
no ip redirects
shutdown
end
if iam going wrong pls apologies
09-22-2009 08:03 AM
you will most likely get an overlapping ip address error and it won't let you do it . Not sure what you accomplish in doing what you are proposing because you have the same address range going down the same interface. It's not really breaking it into different domains as you aren't trunking down to the next device.
09-22-2009 06:28 PM
vinoth
Perhaps it would help if you can explain to us what you are trying to accomplish with this configuration of secondary address. As others have attempted to explain, your secondary does not seem logical since it is a small part of your primary subnet related to your primary address.
In most useage a secondary address (and its associated subnet) are separate and independent from the primary address (and primary subnet). What is the benefit that you seek in configuring a secondary that is already a part of the primary subnet?
I think that I do not agree with Glen about there being an error of overlapping ip address. If you attempt to configure one address (and subnet) on one interface and the other (secondary) address and subnet on another interface, then I agree that the router will say it is an error. But I believe that putting it as primary address and secondary address will be accepted. But what is the benefit of doing this?
HTH
Rick
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