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New Member

Problem with IP addressing

Hello.

I have a 8 port BRI card on a 3660. I am trying to assign IP addresses to all the 8 ports from the same subnet. But the moment I am on the 7th port, it gives an error saying too many addresses on the same subnet. It lets me assign only 6 Ip addresses from the same subnet on the same router.

Any one faced this earlier?

Any help is appreciated.

Thanks in advance.

5 REPLIES
New Member

Re: Problem with IP addressing

Hi.

First of all, the router shouldn't let you configure the same subnet on different interfaces... What subnet mask are you using?

Rgds,

NM

New Member

Re: Problem with IP addressing

Hi.

Thanks for the response.

I am trying to assign IP addresses from this subnet:

10.11.7.192/26. I can assign IP addresses from 10.11.7.193/26 to 10.11.7.198/26 to the first 6 interfaces of the same 8-port BRI card on the same 3660 router. But the moment I get to the 7th port and try to assign 10.11.7.199/26, it says too many IP addresses from the 10.11.7.192 subnet.

I had heard Cisco routers let us assign IP addresses from the same subnet to multiple interfaces on the same router for load balancing purposes. But is 6 the maximum I can assign?

I am running IOS version 12.1(3a)T1.

Any help/clarification is appreciated.

Thanks.

New Member

Re: Problem with IP addressing

Hi.

If you say you can do it... I'm not aware of that "feature". It's weird, because how does the router route among those interfaces?

NM

New Member

Re: Problem with IP addressing

Hi

Yes, you can assign ip address from the same sub-net on point-to-point interfaces only (you can even use the same IP address), the maximum number of interfaces is 6. (search for max-paths on cco)

I've configued this once on a network that had multiple STM1's between nodes. I assigned the same /30 ip address to each STM1. (good way to save IP addresses)

i.e

Local End (Router A)

=========

interface pos1/0

ip address 10.1.1.1 255.255.255.252

!

interface pos1/1

ip address 10.1.1.1 255.255.255.252

!

Remote End (Router B)

==========

interface loopback0

ip address 20.1.1.1 255.255.255.255

!

interface pos1/0

ip address 10.1.1.2 255.255.255.252

!

interface pos1/1

ip address 10.1.1.2 255.255.255.252

!

if routing is enabled for the above interfaces in this network, you would see the following from router A

sh ip route 20.1.1.1

20.1.1.1 via 10.1.1.2, pos1/0

via 10.1.1.2, pos1/1

(route metric info omitted)

Traffic will then load balance accross both pos interfaces (maximum paths = 6).

New Member

Re: Problem with IP addressing

Thanks.

We're always learning!

Rgds.

NM

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